[RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Abinash Singh]

The function serial8250_probe_acpi() in 8250_platform.c triggered a
    frame size warning:
drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_acpi’:
drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch reduces the stack usage by dynamically allocating the
    `uart` structure using kmalloc(), rather than placing it on
    the stack. This eliminates the overflow warning and improves kernel
    robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
The stack usage was further confirmed by using -fstack-usage flag.
it was using 1200 bytes:
..............................
drivers/tty/serial/8250/8250_platform.c:110:12:serial8250_probe_acpi	1200	static
drivers/tty/serial/8250/8250_platform.c:351:20:serial8250_exit	16	static
......................................
After applying the patch it becomes :
.........
It doesn't show up in stack usage  and warning is fixed.
.......
This function is used for probing . So dynamic allocation will not create
any issues.

Thank You
---
 drivers/tty/serial/8250/8250_platform.c | 29 +++++++++++++++----------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index c0343bfb8064..f7f9c5036d39 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -15,7 +15,7 @@
 #include <linux/moduleparam.h>
 #include <linux/once.h>
 #include <linux/platform_device.h>
-
+#include <linux/cleanup.h>
 #include <linux/serial_8250.h>
 
 #ifdef CONFIG_SPARC
@@ -110,41 +110,46 @@ void __init serial8250_isa_init_ports(void)
 static int serial8250_probe_acpi(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
-	struct uart_8250_port uart = { };
+	struct uart_8250_port *uart __free(kfree) = NULL;
 	struct resource *regs;
 	int ret, line;
 
+	uart = kmalloc(sizeof(*uart), GFP_KERNEL);
+	if (!uart)
+		return -ENOMEM;
+	memset(uart, 0, sizeof(*uart));
+
 	regs = platform_get_mem_or_io(pdev, 0);
 	if (!regs)
 		return dev_err_probe(dev, -EINVAL, "no registers defined\n");
 
 	switch (resource_type(regs)) {
 	case IORESOURCE_IO:
-		uart.port.iobase = regs->start;
+		uart->port.iobase = regs->start;
 		break;
 	case IORESOURCE_MEM:
-		uart.port.mapbase = regs->start;
-		uart.port.mapsize = resource_size(regs);
-		uart.port.flags = UPF_IOREMAP;
+		uart->port.mapbase = regs->start;
+		uart->port.mapsize = resource_size(regs);
+		uart->port.flags = UPF_IOREMAP;
 		break;
 	default:
 		return -EINVAL;
 	}
 
 	/* default clock frequency */
-	uart.port.uartclk = 1843200;
-	uart.port.type = PORT_16550A;
-	uart.port.dev = &pdev->dev;
-	uart.port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
+	uart->port.uartclk = 1843200;
+	uart->port.type = PORT_16550A;
+	uart->port.dev = &pdev->dev;
+	uart->port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
 
-	ret = uart_read_and_validate_port_properties(&uart.port);
+	ret = uart_read_and_validate_port_properties(&uart->port);
 	/* no interrupt -> fall back to polling */
 	if (ret == -ENXIO)
 		ret = 0;
 	if (ret)
 		return ret;
 
-	line = serial8250_register_8250_port(&uart);
+	line = serial8250_register_8250_port(uart);
 	if (line < 0)
 		return line;
 
-- 
2.50.1

[RFC PATCH 2/2] tty: serial/8250: Fix build warning in serial8250_probe_platform()

[Abinash Singh]

    The function serial8250_probe_platform() in 8250_platform.c triggered a
        frame size warning:
    drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_platform.isra’:
drivers/tty/serial/8250/8250_platform.c:201:1: warning: the frame size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch reduces the stack usage by dynamically allocating the
`uart` structure using kmalloc(), rather than placing it on
the stack. This eliminates the overflow warning and improves kernel
robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
The stack usage was further confirmed by using -fstack-usage flag.
it was usiing 1248 bytes:
..............................
drivers/tty/serial/8250/8250_platform.c:154:12:serial8250_probe_platform.isra	1248	dynamic,bounded
drivers/tty/serial/8250/8250_platform.c:208:12:serial8250_probe	16	static
......................................
After applying the patch it becomes :
.........
It doesn't show up in stack usage  and warning is fixed.
.......
This function is used for probing . So dynamic allocation will not create
any issues.

Thank You
---
 drivers/tty/serial/8250/8250_platform.c | 63 +++++++++++++------------
 1 file changed, 33 insertions(+), 30 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index f7f9c5036d39..86816d9b32ce 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -158,43 +158,46 @@ static int serial8250_probe_acpi(struct platform_device *pdev)
 
 static int serial8250_probe_platform(struct platform_device *dev, struct plat_serial8250_port *p)
 {
-	struct uart_8250_port uart;
+	struct uart_8250_port *uart __free(kfree) = NULL;
 	int ret, i, irqflag = 0;
 
-	memset(&uart, 0, sizeof(uart));
+	uart = kmalloc(sizeof(*uart), GFP_KERNEL);
+	if (!uart)
+		return -ENOMEM;
+	memset(uart, 0, sizeof(*uart));
 
 	if (share_irqs)
 		irqflag = IRQF_SHARED;
 
 	for (i = 0; p && p->flags != 0; p++, i++) {
-		uart.port.iobase	= p->iobase;
-		uart.port.membase	= p->membase;
-		uart.port.irq		= p->irq;
-		uart.port.irqflags	= p->irqflags;
-		uart.port.uartclk	= p->uartclk;
-		uart.port.regshift	= p->regshift;
-		uart.port.iotype	= p->iotype;
-		uart.port.flags		= p->flags;
-		uart.port.mapbase	= p->mapbase;
-		uart.port.mapsize	= p->mapsize;
-		uart.port.hub6		= p->hub6;
-		uart.port.has_sysrq	= p->has_sysrq;
-		uart.port.private_data	= p->private_data;
-		uart.port.type		= p->type;
-		uart.bugs		= p->bugs;
-		uart.port.serial_in	= p->serial_in;
-		uart.port.serial_out	= p->serial_out;
-		uart.dl_read		= p->dl_read;
-		uart.dl_write		= p->dl_write;
-		uart.port.handle_irq	= p->handle_irq;
-		uart.port.handle_break	= p->handle_break;
-		uart.port.set_termios	= p->set_termios;
-		uart.port.set_ldisc	= p->set_ldisc;
-		uart.port.get_mctrl	= p->get_mctrl;
-		uart.port.pm		= p->pm;
-		uart.port.dev		= &dev->dev;
-		uart.port.irqflags	|= irqflag;
-		ret = serial8250_register_8250_port(&uart);
+		uart->port.iobase	= p->iobase;
+		uart->port.membase	= p->membase;
+		uart->port.irq		= p->irq;
+		uart->port.irqflags	= p->irqflags;
+		uart->port.uartclk	= p->uartclk;
+		uart->port.regshift	= p->regshift;
+		uart->port.iotype	= p->iotype;
+		uart->port.flags		= p->flags;
+		uart->port.mapbase	= p->mapbase;
+		uart->port.mapsize	= p->mapsize;
+		uart->port.hub6		= p->hub6;
+		uart->port.has_sysrq	= p->has_sysrq;
+		uart->port.private_data	= p->private_data;
+		uart->port.type		= p->type;
+		uart->bugs		= p->bugs;
+		uart->port.serial_in	= p->serial_in;
+		uart->port.serial_out	= p->serial_out;
+		uart->dl_read		= p->dl_read;
+		uart->dl_write		= p->dl_write;
+		uart->port.handle_irq	= p->handle_irq;
+		uart->port.handle_break	= p->handle_break;
+		uart->port.set_termios	= p->set_termios;
+		uart->port.set_ldisc	= p->set_ldisc;
+		uart->port.get_mctrl	= p->get_mctrl;
+		uart->port.pm		= p->pm;
+		uart->port.dev		= &dev->dev;
+		uart->port.irqflags	|= irqflag;
+		ret = serial8250_register_8250_port(uart);
 		if (ret < 0) {
 			dev_err(&dev->dev, "unable to register port at index %d "
 				"(IO%lx MEM%llx IRQ%d): %d\n", i,
-- 
2.50.1

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Andy Shevchenko]

On Wed, Aug 06, 2025 at 01:21:54AM +0530, Abinash Singh wrote:
> The function serial8250_probe_acpi() in 8250_platform.c triggered a
>     frame size warning:
> drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_acpi’:
> drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> This patch reduces the stack usage by dynamically allocating the
>     `uart` structure using kmalloc(), rather than placing it on
>     the stack. This eliminates the overflow warning and improves kernel
>     robustness.

...

>  #include <linux/platform_device.h>
> -

Stray change.

> +#include <linux/cleanup.h>

Please, keep it ordered.

>  #include <linux/serial_8250.h>

...

>  	struct device *dev = &pdev->dev;
> -	struct uart_8250_port uart = { };
> +	struct uart_8250_port *uart __free(kfree) = NULL;
>  	struct resource *regs;
>  	int ret, line;
>  
> +	uart = kmalloc(sizeof(*uart), GFP_KERNEL);

Just declare variable here, as the NULL assignment may lead to subtle issues.

> +	if (!uart)
> +		return -ENOMEM;

> +	memset(uart, 0, sizeof(*uart));

We have kzalloc() for this.


-- 
With Best Regards,
Andy Shevchenko

Re: [RFC PATCH 2/2] tty: serial/8250: Fix build warning in serial8250_probe_platform()

[Andy Shevchenko]

On Wed, Aug 06, 2025 at 01:21:55AM +0530, Abinash Singh wrote:
>     The function serial8250_probe_platform() in 8250_platform.c triggered a
>         frame size warning:
>     drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_platform.isra’:
> drivers/tty/serial/8250/8250_platform.c:201:1: warning: the frame size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> This patch reduces the stack usage by dynamically allocating the
> `uart` structure using kmalloc(), rather than placing it on
> the stack. This eliminates the overflow warning and improves kernel
> robustness.

Same comments as per patch 1.
Also, here in the Subject you have an extra space. Actually, check output of

git log --oneline --no-merges -- drivers/tty/serial/8250/8250_platform.c

to have a hint how the Subject should look like.

...

The approach in general is okay to me.

-- 
With Best Regards,
Andy Shevchenko

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Arnd Bergmann]

On Tue, Aug 5, 2025, at 21:51, Abinash Singh wrote:
> The function serial8250_probe_acpi() in 8250_platform.c triggered a
>     frame size warning:
> drivers/tty/serial/8250/8250_platform.c: In function 
> ‘serial8250_probe_acpi’:
> drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size 
> of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]

Hi Abinash,

I've seen this one as well in some configurations, thanks
for helping out addressing it!

> This patch reduces the stack usage by dynamically allocating the
>     `uart` structure using kmalloc(), rather than placing it on
>     the stack. This eliminates the overflow warning and improves kernel
>     robustness.

The same problem does show up in a lot of 8250 driver variants,
plus a couple that have it in theory but don't run into the
1024 byte limit:

drivers/char/mwave/mwavedd.c-static int register_serial_portandirq(unsigned int port, int irq)
drivers/char/mwave/mwavedd.c-{
drivers/char/mwave/mwavedd.c:   struct uart_8250_port uart;

drivers/ptp/ptp_ocp.c-ptp_ocp_serial_line(struct ptp_ocp *bp, struct ocp_resource *r)
drivers/ptp/ptp_ocp.c-{
drivers/ptp/ptp_ocp.c-  struct pci_dev *pdev = bp->pdev;
drivers/ptp/ptp_ocp.c:  struct uart_8250_port uart;

drivers/tty/serial/8250/8250_acorn.c-serial_card_probe(struct expansion_card *ec, const struct ecard_id *id)
drivers/tty/serial/8250/8250_acorn.c-{
drivers/tty/serial/8250/8250_acorn.c:   struct uart_8250_port uart;

drivers/tty/serial/8250/8250_bcm2835aux.c-static int bcm2835aux_serial_probe(struct platform_device *pdev)
drivers/tty/serial/8250/8250_bcm2835aux.c-{
drivers/tty/serial/8250/8250_bcm2835aux.c:      struct uart_8250_port up = { };

In total, I see 34 drivers using this exact pattern for 
their probe function, and ideally we would to to fix them
all to do it some other way.

Note how serial8250_register_8250_port() ands up just copying
individual members of the passed uart_8250_port structure into
the global array of the same type, so one way of addressing
this would be to use a structure for initialization that only
contains a subset of the uart_8250_port members and can still
be allocated on the stack, or possibly be constant.

There is already a 'struct plat_serial8250_port', which some
(mostly ancient) drivers use to register a 8250 compatible
uart through the 8250_platform driver. That driver has
a number of problems, so I don't really want to expand its
usage, but it may be possible to use a single structure
for both purposes.

      Arnd

[PATCH v2 0/2] serial: 8250_platform: Reduce stack usage in probe functions

[Abinash Singh]

Hello,

I’m very happy and grateful to receive such valuable feedback and
support from you all.I’ve carefully reviewed the comments and
have applied the suggested changes in this v2 series.
Please let me know if there is anything else I can
improve or correct further. I truly appreciate your
time and guidance.

Changes in v2:
- Use kzalloc() instead of kmalloc() + memset()
- Removed unnecessary NULL initialization
- Fixed include ordering
- Improved subject line clarity

Thank you very much !

Best regards,
Abinash

Abinash Singh (2):
  serial: 8250_platform: Reduce stack usage in serial8250_probe_acpi()
  serial: 8250_platform: Reduce stack usage in
    serial8250_probe_platform()

 drivers/tty/serial/8250/8250_platform.c | 87 +++++++++++++------------
 1 file changed, 46 insertions(+), 41 deletions(-)

-- 
2.50.1

[PATCH v2 1/2] serial: 8250_platform: Reduce stack usage in serial8250_probe_acpi()

[Abinash Singh]

The function serial8250_probe_acpi() in 8250_platform.c triggered a
    frame size warning:
drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_acpi’:
drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch reduces the stack usage by dynamically allocating the
`uart` structure using kzalloc(), rather than placing it on
the stack. This eliminates the overflow warning and improves kernel
robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
 drivers/tty/serial/8250/8250_platform.c | 26 ++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index c0343bfb8064..50cec2413aeb 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -10,6 +10,7 @@
  */
 #include <linux/acpi.h>
 #include <linux/array_size.h>
+#include <linux/cleanup.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
@@ -110,9 +111,12 @@ void __init serial8250_isa_init_ports(void)
 static int serial8250_probe_acpi(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
-	struct uart_8250_port uart = { };
 	struct resource *regs;
 	int ret, line;
+	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
+
+	if (!uart)
+		return -ENOMEM;
 
 	regs = platform_get_mem_or_io(pdev, 0);
 	if (!regs)
@@ -120,31 +124,31 @@ static int serial8250_probe_acpi(struct platform_device *pdev)
 
 	switch (resource_type(regs)) {
 	case IORESOURCE_IO:
-		uart.port.iobase = regs->start;
+		uart->port.iobase = regs->start;
 		break;
 	case IORESOURCE_MEM:
-		uart.port.mapbase = regs->start;
-		uart.port.mapsize = resource_size(regs);
-		uart.port.flags = UPF_IOREMAP;
+		uart->port.mapbase = regs->start;
+		uart->port.mapsize = resource_size(regs);
+		uart->port.flags = UPF_IOREMAP;
 		break;
 	default:
 		return -EINVAL;
 	}
 
 	/* default clock frequency */
-	uart.port.uartclk = 1843200;
-	uart.port.type = PORT_16550A;
-	uart.port.dev = &pdev->dev;
-	uart.port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
+	uart->port.uartclk = 1843200;
+	uart->port.type = PORT_16550A;
+	uart->port.dev = &pdev->dev;
+	uart->port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
 
-	ret = uart_read_and_validate_port_properties(&uart.port);
+	ret = uart_read_and_validate_port_properties(&uart->port);
 	/* no interrupt -> fall back to polling */
 	if (ret == -ENXIO)
 		ret = 0;
 	if (ret)
 		return ret;
 
-	line = serial8250_register_8250_port(&uart);
+	line = serial8250_register_8250_port(uart);
 	if (line < 0)
 		return line;
 
-- 
2.50.1

[PATCH v2 2/2] serial: 8250_platform: Reduce stack usage in serial8250_probe_platform()

[Abinash Singh]

The function serial8250_probe_platform() in 8250_platform.c triggered a
        frame size warning:
drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_platform.isra’:
drivers/tty/serial/8250/8250_platform.c:201:1: warning: the frame size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch reduces the stack usage by dynamically allocating the
`uart` structure using kzalloc(), rather than placing it on
the stack. This eliminates the overflow warning and improves kernel
robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
 drivers/tty/serial/8250/8250_platform.c | 61 +++++++++++++------------
 1 file changed, 31 insertions(+), 30 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index 50cec2413aeb..0baedc7ff6e9 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -157,43 +157,44 @@ static int serial8250_probe_acpi(struct platform_device *pdev)
 
 static int serial8250_probe_platform(struct platform_device *dev, struct plat_serial8250_port *p)
 {
-	struct uart_8250_port uart;
 	int ret, i, irqflag = 0;
+	struct uart_8250_port *uart = kzalloc(sizeof(*uart), GFP_KERNEL);
 
-	memset(&uart, 0, sizeof(uart));
+	if (!uart)
+		return -ENOMEM;
 
 	if (share_irqs)
 		irqflag = IRQF_SHARED;
 
 	for (i = 0; p && p->flags != 0; p++, i++) {
-		uart.port.iobase	= p->iobase;
-		uart.port.membase	= p->membase;
-		uart.port.irq		= p->irq;
-		uart.port.irqflags	= p->irqflags;
-		uart.port.uartclk	= p->uartclk;
-		uart.port.regshift	= p->regshift;
-		uart.port.iotype	= p->iotype;
-		uart.port.flags		= p->flags;
-		uart.port.mapbase	= p->mapbase;
-		uart.port.mapsize	= p->mapsize;
-		uart.port.hub6		= p->hub6;
-		uart.port.has_sysrq	= p->has_sysrq;
-		uart.port.private_data	= p->private_data;
-		uart.port.type		= p->type;
-		uart.bugs		= p->bugs;
-		uart.port.serial_in	= p->serial_in;
-		uart.port.serial_out	= p->serial_out;
-		uart.dl_read		= p->dl_read;
-		uart.dl_write		= p->dl_write;
-		uart.port.handle_irq	= p->handle_irq;
-		uart.port.handle_break	= p->handle_break;
-		uart.port.set_termios	= p->set_termios;
-		uart.port.set_ldisc	= p->set_ldisc;
-		uart.port.get_mctrl	= p->get_mctrl;
-		uart.port.pm		= p->pm;
-		uart.port.dev		= &dev->dev;
-		uart.port.irqflags	|= irqflag;
-		ret = serial8250_register_8250_port(&uart);
+		uart->port.iobase	= p->iobase;
+		uart->port.membase	= p->membase;
+		uart->port.irq		= p->irq;
+		uart->port.irqflags	= p->irqflags;
+		uart->port.uartclk	= p->uartclk;
+		uart->port.regshift	= p->regshift;
+		uart->port.iotype	= p->iotype;
+		uart->port.flags		= p->flags;
+		uart->port.mapbase	= p->mapbase;
+		uart->port.mapsize	= p->mapsize;
+		uart->port.hub6		= p->hub6;
+		uart->port.has_sysrq	= p->has_sysrq;
+		uart->port.private_data	= p->private_data;
+		uart->port.type		= p->type;
+		uart->bugs		= p->bugs;
+		uart->port.serial_in	= p->serial_in;
+		uart->port.serial_out	= p->serial_out;
+		uart->dl_read		= p->dl_read;
+		uart->dl_write		= p->dl_write;
+		uart->port.handle_irq	= p->handle_irq;
+		uart->port.handle_break	= p->handle_break;
+		uart->port.set_termios	= p->set_termios;
+		uart->port.set_ldisc	= p->set_ldisc;
+		uart->port.get_mctrl	= p->get_mctrl;
+		uart->port.pm		= p->pm;
+		uart->port.dev		= &dev->dev;
+		uart->port.irqflags	|= irqflag;
+		ret = serial8250_register_8250_port(uart);
 		if (ret < 0) {
 			dev_err(&dev->dev, "unable to register port at index %d "
 				"(IO%lx MEM%llx IRQ%d): %d\n", i,
-- 
2.50.1

Re: [PATCH v2 0/2] serial: 8250_platform: Reduce stack usage in probe functions

[Andy Shevchenko]

On Thu, Aug 07, 2025 at 01:40:45AM +0530, Abinash Singh wrote:
> Hello,
> 
> I’m very happy and grateful to receive such valuable feedback and
> support from you all.I’ve carefully reviewed the comments and
> have applied the suggested changes in this v2 series.
> Please let me know if there is anything else I can
> improve or correct further. I truly appreciate your
> time and guidance.

Have you had a chance to see Arnd's comments?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/2] serial: 8250_platform: Reduce stack usage in serial8250_probe_acpi()

[Andy Shevchenko]

On Thu, Aug 07, 2025 at 01:40:46AM +0530, Abinash Singh wrote:
> The function serial8250_probe_acpi() in 8250_platform.c triggered a
>     frame size warning:
> drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_acpi’:
> drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> This patch reduces the stack usage by dynamically allocating the
> `uart` structure using kzalloc(), rather than placing it on
> the stack. This eliminates the overflow warning and improves kernel
> robustness.

...

>  	struct resource *regs;
>  	int ret, line;
> +	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
> +
> +	if (!uart)
> +		return -ENOMEM;

For cleanup (__free() in particular) we allow to mix definitions with the code
and it would be natural to have it a bit different

	struct resource *regs;
	int ret, line;

	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
	if (!uart)
		return -ENOMEM;

(In your case just a blank line placement is one line above.)

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/2] serial: 8250_platform: Reduce stack usage in serial8250_probe_platform()

[Andy Shevchenko]

On Thu, Aug 07, 2025 at 01:40:47AM +0530, Abinash Singh wrote:
> The function serial8250_probe_platform() in 8250_platform.c triggered a
>         frame size warning:
> drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_platform.isra’:
> drivers/tty/serial/8250/8250_platform.c:201:1: warning: the frame size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> 
> This patch reduces the stack usage by dynamically allocating the
> `uart` structure using kzalloc(), rather than placing it on
> the stack. This eliminates the overflow warning and improves kernel
> robustness.

...

> -	struct uart_8250_port uart;
>  	int ret, i, irqflag = 0;
> +	struct uart_8250_port *uart = kzalloc(sizeof(*uart), GFP_KERNEL);
>  
> -	memset(&uart, 0, sizeof(uart));
> +	if (!uart)
> +		return -ENOMEM;

Missed __free and same comment as in previous patch. An rule of thumb: avoid
such a split in the future, try to have an assignment and followed up check go
together, it 's easier to maintain and less prone to subtle mistakes.


-- 
With Best Regards,
Andy Shevchenko

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Abinash Singh]

On Wed, Aug 6, 2025 at 12:32 PM Arnd Bergmann <arnd@arndb.de> wrote:
> Hi Abinash,
Hi ,Arnd

> I've seen this one as well in some configurations, thanks
> for helping out addressing it!

You are welcome ..! ,
 I have a patch accepted in that
commit : (3df63fa8f2af) dma: dw-edma: Fix build warning in dw_edma_pcie_probe()

In general, using dynamic memory allocation in functions that are not in
performance-critical paths—like probe routines—is a reasonable approach
to reduce large stack usage without performance penalties.

> The same problem does show up in a lot of 8250 driver variants,
> plus a couple that have it in theory but don't run into the
> 1024 byte limit:

You are absolutely right. I compiled these drivers with
"-fstack-usage" flag which generated the stack usage of each function.

> drivers/char/mwave/mwavedd.c-static int register_serial_portandirq(unsigned int port, int irq)
> drivers/char/mwave/mwavedd.c-{
> drivers/char/mwave/mwavedd.c:   struct uart_8250_port uart;
>
// stack usage using -fstack-usage in bytes
drivers/char/mwave/mwavedd.c:123:13:mwave_ioctl 216 static
drivers/char/mwave/mwavedd.c:437:12:register_serial_portandirq 976 static

> drivers/ptp/ptp_ocp.c-ptp_ocp_serial_line(struct ptp_ocp *bp, struct ocp_resource *r)
> drivers/ptp/ptp_ocp.c-{
> drivers/ptp/ptp_ocp.c-  struct pci_dev *pdev = bp->pdev;
> drivers/ptp/ptp_ocp.c:  struct uart_8250_port uart;
>
// stack usage using -fstack-usage bytes
drivers/ptp/ptp_ocp.c:2273:1:ptp_ocp_serial_line.isra 984 static
drivers/ptp/ptp_ocp.c:2295:1:ptp_ocp_register_serial 32 static

similar results for other drivers mentioned.....

> In total, I see 34 drivers using this exact pattern for
> their probe function, and ideally we would to to fix them
> all to do it some other way.
>
Dynamic memory allocation is acceptable in probe functions,
as the introduced delay is minimal and these functions are
called infrequently.

> Note how serial8250_register_8250_port() ands up just copying
> individual members of the passed uart_8250_port structure into
> the global array of the same type, so one way of addressing
> this would be to use a structure for initialization that only
> contains a subset of the uart_8250_port members and can still
> be allocated on the stack, or possibly be constant.
>
This is a very good approach because it confines dynamic
memory allocation to the probe function, where it is acceptable.
In most other functions, dynamic allocation is generally not suitable.

I also reviewed a few functions and noticed that only a small number
of fields from the stack-allocated struct uart_8250_port are
actually used. Therefore, this method is well-suited for such cases.

> There is already a 'struct plat_serial8250_port', which some
> (mostly ancient) drivers use to register a 8250 compatible
> uart through the 8250_platform driver. That driver has
> a number of problems, so I don't really want to expand its
> usage, but it may be possible to use a single structure
> for both purposes.
>
To proceed, we can introduce a smaller struct containing only the
required fields.
In the probe function, the choice between dynamic allocation and using
this reduced
struct can be made based on the number of fields used in each specific scenario.

Thanks.

Abinash

[PATCH v3 0/2] serial: 8250_platform: Reduce stack usage in probe functions

[Abinash Singh]

On Wed, 6 Aug 2025 23:39 Andy Shevchenko wrote:
> Have you had a chance to see Arnd's comments?
>
Yeah ,I have made comments on that.
Please check that and provide feedback.

Hi,
Apologies for not reviewing the patch carefully before submitting it.
It's 3 A.M. here, and I’m still up, so I missed it


Changes in v3:
- fix missing __free(kfree)
- mixed defination with code for cleanup attribute

And I will remember the rule of thumb to mix the code and defination
in such cases.

Thank you very much !

Best regards,
Abinash

Abinash Singh (2):
  serial: 8250_platform: Reduce stack usage in serial8250_probe_acpi()
  serial: 8250_platform: Reduce stack usage in
    serial8250_probe_platform()

 drivers/tty/serial/8250/8250_platform.c | 87 +++++++++++++------------
 1 file changed, 46 insertions(+), 41 deletions(-)

-- 
2.50.1

[PATCH v3 1/2] serial: 8250_platform: Reduce stack usage in serial8250_probe_acpi()

[Abinash Singh]

The function serial8250_probe_acpi() in 8250_platform.c triggered a
    frame size warning:
drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_acpi’:
drivers/tty/serial/8250/8250_platform.c:152:1: warning: the frame size of 1160 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch reduces the stack usage by dynamically allocating the
`uart` structure using kzalloc(), rather than placing it on
the stack. This eliminates the overflow warning and improves kernel
robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
 drivers/tty/serial/8250/8250_platform.c | 26 ++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index c0343bfb8064..9938aeb917d8 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -10,6 +10,7 @@
  */
 #include <linux/acpi.h>
 #include <linux/array_size.h>
+#include <linux/cleanup.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
@@ -110,41 +111,44 @@ void __init serial8250_isa_init_ports(void)
 static int serial8250_probe_acpi(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
-	struct uart_8250_port uart = { };
 	struct resource *regs;
 	int ret, line;
 
+	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
+	if (!uart)
+		return -ENOMEM;
+
 	regs = platform_get_mem_or_io(pdev, 0);
 	if (!regs)
 		return dev_err_probe(dev, -EINVAL, "no registers defined\n");
 
 	switch (resource_type(regs)) {
 	case IORESOURCE_IO:
-		uart.port.iobase = regs->start;
+		uart->port.iobase = regs->start;
 		break;
 	case IORESOURCE_MEM:
-		uart.port.mapbase = regs->start;
-		uart.port.mapsize = resource_size(regs);
-		uart.port.flags = UPF_IOREMAP;
+		uart->port.mapbase = regs->start;
+		uart->port.mapsize = resource_size(regs);
+		uart->port.flags = UPF_IOREMAP;
 		break;
 	default:
 		return -EINVAL;
 	}
 
 	/* default clock frequency */
-	uart.port.uartclk = 1843200;
-	uart.port.type = PORT_16550A;
-	uart.port.dev = &pdev->dev;
-	uart.port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
+	uart->port.uartclk = 1843200;
+	uart->port.type = PORT_16550A;
+	uart->port.dev = &pdev->dev;
+	uart->port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
 
-	ret = uart_read_and_validate_port_properties(&uart.port);
+	ret = uart_read_and_validate_port_properties(&uart->port);
 	/* no interrupt -> fall back to polling */
 	if (ret == -ENXIO)
 		ret = 0;
 	if (ret)
 		return ret;
 
-	line = serial8250_register_8250_port(&uart);
+	line = serial8250_register_8250_port(uart);
 	if (line < 0)
 		return line;
 
-- 
2.50.1

[PATCH v3 2/2] serial: 8250_platform: Reduce stack usage in serial8250_probe_platform()

[Abinash Singh]

 The function serial8250_probe_platform() in 8250_platform.c triggered a
        frame size warning:
drivers/tty/serial/8250/8250_platform.c: In function ‘serial8250_probe_platform.isra’:
drivers/tty/serial/8250/8250_platform.c:201:1: warning: the frame size of 1184 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This patch reduces the stack usage by dynamically allocating the
`uart` structure using kzalloc(), rather than placing it on
the stack. This eliminates the overflow warning and improves kernel
robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
 drivers/tty/serial/8250/8250_platform.c | 61 +++++++++++++------------
 1 file changed, 31 insertions(+), 30 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index 9938aeb917d8..b27981340e76 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -157,43 +157,44 @@ static int serial8250_probe_acpi(struct platform_device *pdev)
 
 static int serial8250_probe_platform(struct platform_device *dev, struct plat_serial8250_port *p)
 {
-	struct uart_8250_port uart;
 	int ret, i, irqflag = 0;
 
-	memset(&uart, 0, sizeof(uart));
+	struct uart_8250_port *uart __free(kfree) = kzalloc(sizeof(*uart), GFP_KERNEL);
+	if (!uart)
+		return -ENOMEM;
 
 	if (share_irqs)
 		irqflag = IRQF_SHARED;
 
 	for (i = 0; p && p->flags != 0; p++, i++) {
-		uart.port.iobase	= p->iobase;
-		uart.port.membase	= p->membase;
-		uart.port.irq		= p->irq;
-		uart.port.irqflags	= p->irqflags;
-		uart.port.uartclk	= p->uartclk;
-		uart.port.regshift	= p->regshift;
-		uart.port.iotype	= p->iotype;
-		uart.port.flags		= p->flags;
-		uart.port.mapbase	= p->mapbase;
-		uart.port.mapsize	= p->mapsize;
-		uart.port.hub6		= p->hub6;
-		uart.port.has_sysrq	= p->has_sysrq;
-		uart.port.private_data	= p->private_data;
-		uart.port.type		= p->type;
-		uart.bugs		= p->bugs;
-		uart.port.serial_in	= p->serial_in;
-		uart.port.serial_out	= p->serial_out;
-		uart.dl_read		= p->dl_read;
-		uart.dl_write		= p->dl_write;
-		uart.port.handle_irq	= p->handle_irq;
-		uart.port.handle_break	= p->handle_break;
-		uart.port.set_termios	= p->set_termios;
-		uart.port.set_ldisc	= p->set_ldisc;
-		uart.port.get_mctrl	= p->get_mctrl;
-		uart.port.pm		= p->pm;
-		uart.port.dev		= &dev->dev;
-		uart.port.irqflags	|= irqflag;
-		ret = serial8250_register_8250_port(&uart);
+		uart->port.iobase	= p->iobase;
+		uart->port.membase	= p->membase;
+		uart->port.irq		= p->irq;
+		uart->port.irqflags	= p->irqflags;
+		uart->port.uartclk	= p->uartclk;
+		uart->port.regshift	= p->regshift;
+		uart->port.iotype	= p->iotype;
+		uart->port.flags		= p->flags;
+		uart->port.mapbase	= p->mapbase;
+		uart->port.mapsize	= p->mapsize;
+		uart->port.hub6		= p->hub6;
+		uart->port.has_sysrq	= p->has_sysrq;
+		uart->port.private_data	= p->private_data;
+		uart->port.type		= p->type;
+		uart->bugs		= p->bugs;
+		uart->port.serial_in	= p->serial_in;
+		uart->port.serial_out	= p->serial_out;
+		uart->dl_read		= p->dl_read;
+		uart->dl_write		= p->dl_write;
+		uart->port.handle_irq	= p->handle_irq;
+		uart->port.handle_break	= p->handle_break;
+		uart->port.set_termios	= p->set_termios;
+		uart->port.set_ldisc	= p->set_ldisc;
+		uart->port.get_mctrl	= p->get_mctrl;
+		uart->port.pm		= p->pm;
+		uart->port.dev		= &dev->dev;
+		uart->port.irqflags	|= irqflag;
+		ret = serial8250_register_8250_port(uart);
 		if (ret < 0) {
 			dev_err(&dev->dev, "unable to register port at index %d "
 				"(IO%lx MEM%llx IRQ%d): %d\n", i,
-- 
2.50.1

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Jiri Slaby]

On 06. 08. 25, 9:01, Arnd Bergmann wrote:
> Note how serial8250_register_8250_port() ands up just copying
> individual members of the passed uart_8250_port structure into
> the global array of the same type, so one way of addressing
> this would be to use a structure for initialization that only
> contains a subset of the uart_8250_port members and can still
> be allocated on the stack, or possibly be constant.

Yes:
https://lore.kernel.org/all/f84c2ee3-77b4-41c4-8517-26dfb44a2276@kernel.org/

-- 
js
suse labs

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Jiri Slaby]

On 07. 08. 25, 7:25, Jiri Slaby wrote:
> On 06. 08. 25, 9:01, Arnd Bergmann wrote:
>> Note how serial8250_register_8250_port() ands up just copying
>> individual members of the passed uart_8250_port structure into
>> the global array of the same type, so one way of addressing
>> this would be to use a structure for initialization that only
>> contains a subset of the uart_8250_port members and can still
>> be allocated on the stack, or possibly be constant.
> 
> Yes:
> https://lore.kernel.org/all/ 
> f84c2ee3-77b4-41c4-8517-26dfb44a2276@kernel.org/

As a PoC, these members from uart_8250_port are really used in 
serial8250_register_8250_port():
struct uart_8250_port2 {
         long unsigned int          iobase;               /*     0     8 */
         resource_size_t            mapbase;              /*     8     8 */
         unsigned char *            membase;              /*    16     8 */
         long unsigned int          irqflags;             /*    24     8 */
         upf_t                      flags;                /*    32     8 */
         enum uart_iotype           iotype;               /*    40     4 */
         unsigned int               tx_loadsz;            /*    44     4 */
         unsigned int               type;                 /*    48     4 */
         u32                        overrun_backoff_time_ms; /*    52 
  4 */
         u32                        capabilities;         /*    56     4 */
         unsigned int               line;                 /*    60     4 */
         /* --- cacheline 1 boundary (64 bytes) --- */
         unsigned int               uartclk;              /*    64     4 */
         unsigned int               ctrl_id;              /*    68     4 */
         unsigned int               port_id;              /*    72     4 */
         unsigned int               irq;                  /*    76     4 */
         unsigned int               fifosize;             /*    80     4 */
         u16                        bugs;                 /*    84     2 */
         u16                        lsr_save_mask;        /*    86     2 */
         unsigned char              regshift;             /*    88     1 */
         unsigned char              hub6;                 /*    89     1 */

         /* XXX 6 bytes hole, try to pack */

         resource_size_t            mapsize;              /*    96     8 */
         struct serial_rs485        rs485;                /*   104    32 */
         /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
         struct serial_rs485        rs485_supported;      /*   136    32 */
         void *                     private_data;         /*   168     8 */
         struct uart_8250_dma *     dma;                  /*   176     8 */
         void                       (*rs485_start_tx)(struct 
uart_8250_port *, bool); /*   184     8 */
         /* --- cacheline 3 boundary (192 bytes) --- */
         void                       (*rs485_stop_tx)(struct 
uart_8250_port *, bool); /*   192     8 */
         void                       (*throttle)(struct uart_port *); /* 
  200     8 */
         void                       (*unthrottle)(struct uart_port *); 
/*   208     8 */
         u32                        (*serial_in)(struct uart_port *, 
unsigned int); /*   216     8 */
         void                       (*serial_out)(struct uart_port *, 
unsigned int, u32); /*   224     8 */
         void                       (*set_termios)(struct uart_port *, 
struct ktermios *, const struct ktermios  *); /*   232     8 */
         void                       (*set_ldisc)(struct uart_port *, 
struct ktermios *); /*   240     8 */
         unsigned int               (*get_mctrl)(struct uart_port *); /* 
   248     8 */
         /* --- cacheline 4 boundary (256 bytes) --- */
         void                       (*set_mctrl)(struct uart_port *, 
unsigned int); /*   256     8 */
         unsigned int               (*get_divisor)(struct uart_port *, 
unsigned int, unsigned int *); /*   264     8 */
         void                       (*set_divisor)(struct uart_port *, 
unsigned int, unsigned int, unsigned int); /*   272     8 */
         int                        (*startup)(struct uart_port *); /* 
280     8 */
         void                       (*shutdown)(struct uart_port *); /* 
  288     8 */
         int                        (*handle_irq)(struct uart_port *); 
/*   296     8 */
         void                       (*pm)(struct uart_port *, unsigned 
int, unsigned int); /*   304     8 */
         void                       (*handle_break)(struct uart_port *); 
/*   312     8 */
         /* --- cacheline 5 boundary (320 bytes) --- */
         int                        (*rs485_config)(struct uart_port *, 
struct ktermios *, struct serial_rs485 *); /*   320     8 */
         struct device *            dev;                  /*   328     8 */
         u32                        (*dl_read)(struct uart_8250_port *); 
/*   336     8 */
         void                       (*dl_write)(struct uart_8250_port *, 
u32); /*   344     8 */

         /* size: 352, cachelines: 6, members: 46 */
         /* sum members: 346, holes: 1, sum holes: 6 */
         /* last cacheline: 32 bytes */
};


-- 
js
suse labs

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Jiri Slaby]

On 07. 08. 25, 8:43, Jiri Slaby wrote:
> On 07. 08. 25, 7:25, Jiri Slaby wrote:
>> On 06. 08. 25, 9:01, Arnd Bergmann wrote:
>>> Note how serial8250_register_8250_port() ands up just copying
>>> individual members of the passed uart_8250_port structure into
>>> the global array of the same type, so one way of addressing
>>> this would be to use a structure for initialization that only
>>> contains a subset of the uart_8250_port members and can still
>>> be allocated on the stack, or possibly be constant.
>>
>> Yes:
>> https://lore.kernel.org/all/ 
>> f84c2ee3-77b4-41c4-8517-26dfb44a2276@kernel.org/
> 
> As a PoC, these members from uart_8250_port are really used in 
> serial8250_register_8250_port():
> struct uart_8250_port2 {
>          long unsigned int          iobase;               /*     0     8 */
>          resource_size_t            mapbase;              /*     8     8 */
>          unsigned char *            membase;              /*    16     8 */
>          long unsigned int          irqflags;             /*    24     8 */
>          upf_t                      flags;                /*    32     8 */
>          enum uart_iotype           iotype;               /*    40     4 */
>          unsigned int               tx_loadsz;            /*    44     4 */
>          unsigned int               type;                 /*    48     4 */
>          u32                        overrun_backoff_time_ms; /*    52  4 */
>          u32                        capabilities;         /*    56     4 */
>          unsigned int               line;                 /*    60     4 */
>          /* --- cacheline 1 boundary (64 bytes) --- */
>          unsigned int               uartclk;              /*    64     4 */
>          unsigned int               ctrl_id;              /*    68     4 */
>          unsigned int               port_id;              /*    72     4 */
>          unsigned int               irq;                  /*    76     4 */
>          unsigned int               fifosize;             /*    80     4 */
>          u16                        bugs;                 /*    84     2 */
>          u16                        lsr_save_mask;        /*    86     2 */
>          unsigned char              regshift;             /*    88     1 */
>          unsigned char              hub6;                 /*    89     1 */
> 
>          /* XXX 6 bytes hole, try to pack */
> 
>          resource_size_t            mapsize;              /*    96     8 */
>          struct serial_rs485        rs485;                /*   104    32 */
>          /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */
>          struct serial_rs485        rs485_supported;      /*   136    32 */
>          void *                     private_data;         /*   168     8 */
>          struct uart_8250_dma *     dma;                  /*   176     8 */

And if in the above link mentioned conversion to ops [1] is finished, we 
would replace all the below by a single pointer to a const ops. The 
struct would be then 176+8.

[1] the two "ops" commits at 
https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git/log/?h=devel

>          void                       (*rs485_start_tx)(struct 
> uart_8250_port *, bool); /*   184     8 */
>          /* --- cacheline 3 boundary (192 bytes) --- */
>          void                       (*rs485_stop_tx)(struct 
> uart_8250_port *, bool); /*   192     8 */
>          void                       (*throttle)(struct uart_port *); /* 
>   200     8 */
>          void                       (*unthrottle)(struct uart_port *); / 
> *   208     8 */
>          u32                        (*serial_in)(struct uart_port *, 
> unsigned int); /*   216     8 */
>          void                       (*serial_out)(struct uart_port *, 
> unsigned int, u32); /*   224     8 */
>          void                       (*set_termios)(struct uart_port *, 
> struct ktermios *, const struct ktermios  *); /*   232     8 */
>          void                       (*set_ldisc)(struct uart_port *, 
> struct ktermios *); /*   240     8 */
>          unsigned int               (*get_mctrl)(struct uart_port *); /* 
>    248     8 */
>          /* --- cacheline 4 boundary (256 bytes) --- */
>          void                       (*set_mctrl)(struct uart_port *, 
> unsigned int); /*   256     8 */
>          unsigned int               (*get_divisor)(struct uart_port *, 
> unsigned int, unsigned int *); /*   264     8 */
>          void                       (*set_divisor)(struct uart_port *, 
> unsigned int, unsigned int, unsigned int); /*   272     8 */
>          int                        (*startup)(struct uart_port *); /* 
> 280     8 */
>          void                       (*shutdown)(struct uart_port *); /* 
>   288     8 */
>          int                        (*handle_irq)(struct uart_port *); / 
> *   296     8 */
>          void                       (*pm)(struct uart_port *, unsigned 
> int, unsigned int); /*   304     8 */
>          void                       (*handle_break)(struct uart_port 
> *); /*   312     8 */
>          /* --- cacheline 5 boundary (320 bytes) --- */
>          int                        (*rs485_config)(struct uart_port *, 
> struct ktermios *, struct serial_rs485 *); /*   320     8 */
>          struct device *            dev;                  /*   328     8 */
>          u32                        (*dl_read)(struct uart_8250_port 
> *); /*   336     8 */
>          void                       (*dl_write)(struct uart_8250_port *, 
> u32); /*   344     8 */
> 
>          /* size: 352, cachelines: 6, members: 46 */
>          /* sum members: 346, holes: 1, sum holes: 6 */
>          /* last cacheline: 32 bytes */
> };
> 
> 

-- 
js
suse labs

Re: [RFC PATCH 1/2] tty: serial/8250: Fix build warning in serial8250_probe_acpi()

[Arnd Bergmann]

On Thu, Aug 7, 2025, at 08:43, Jiri Slaby wrote:
> On 07. 08. 25, 7:25, Jiri Slaby wrote:
>> On 06. 08. 25, 9:01, Arnd Bergmann wrote:
>>> Note how serial8250_register_8250_port() ands up just copying
>>> individual members of the passed uart_8250_port structure into
>>> the global array of the same type, so one way of addressing
>>> this would be to use a structure for initialization that only
>>> contains a subset of the uart_8250_port members and can still
>>> be allocated on the stack, or possibly be constant.
>> 
>> Yes:
>> https://lore.kernel.org/all/ 
>> f84c2ee3-77b4-41c4-8517-26dfb44a2276@kernel.org/
>
> As a PoC, these members from uart_8250_port are really used in 
> serial8250_register_8250_port():

Nice, that does look helpful!

I was thinking about looking for the same members the other
way, seeing which fields are getting initialized by the various
callers, as I expect that by now we have gained a couple of
read-only or write-only members that we don't really need to
pass any more.

I the diff below I have removed all assignments to the local
uart_8250_port structures that get passed into
serial8250_register_8250_port() for reference, but I have
not yet cross-checked them against the members you found.

     Arnd

diff --git a/drivers/char/mwave/mwavedd.c b/drivers/char/mwave/mwavedd.c
index 11272d605ecd..aabf4ea8c63c 100644
--- a/drivers/char/mwave/mwavedd.c
+++ b/drivers/char/mwave/mwavedd.c
@@ -470,11 +470,6 @@ static int register_serial_portandirq(unsigned int port, int irq)
 
 	memset(&uart, 0, sizeof(uart));
 	
-	uart.port.uartclk =  1843200;
-	uart.port.iobase = port;
-	uart.port.irq = irq;
-	uart.port.iotype = UPIO_PORT;
-	uart.port.flags =  UPF_SHARE_IRQ;
 	return serial8250_register_8250_port(&uart);
 }
 
diff --git a/drivers/misc/ibmasm/uart.c b/drivers/misc/ibmasm/uart.c
index 46f4c98c3c85..35ccf8aabedb 100644
--- a/drivers/misc/ibmasm/uart.c
+++ b/drivers/misc/ibmasm/uart.c
@@ -34,12 +34,6 @@ void ibmasm_register_uart(struct service_processor *sp)
 	}
 
 	memset(&uart, 0, sizeof(uart));
-	uart.port.irq		= sp->irq;
-	uart.port.uartclk	= 3686400;
-	uart.port.flags		= UPF_SHARE_IRQ;
-	uart.port.iotype	= UPIO_MEM;
-	uart.port.membase	= iomem_base;
-	uart.port.dev		= sp->dev;
 
 	sp->serial_line = serial8250_register_8250_port(&uart);
 	if (sp->serial_line < 0) {
diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
index d39073dc4072..f5947d5713c0 100644
--- a/drivers/ptp/ptp_ocp.c
+++ b/drivers/ptp/ptp_ocp.c
@@ -2279,14 +2279,6 @@ ptp_ocp_serial_line(struct ptp_ocp *bp, struct ocp_resource *r)
 	 * the serial port device claim and release the pci resource.
 	 */
 	memset(&uart, 0, sizeof(uart));
-	uart.port.dev = &pdev->dev;
-	uart.port.iotype = UPIO_MEM;
-	uart.port.regshift = 2;
-	uart.port.mapbase = pci_resource_start(pdev, 0) + r->offset;
-	uart.port.irq = pci_irq_vector(pdev, r->irq_vec);
-	uart.port.uartclk = 50000000;
-	uart.port.flags = UPF_FIXED_TYPE | UPF_IOREMAP | UPF_NO_THRE_TEST;
-	uart.port.type = PORT_16550A;
 
 	return serial8250_register_8250_port(&uart);
 }
diff --git a/drivers/tty/serial/8250/8250_acorn.c b/drivers/tty/serial/8250/8250_acorn.c
index 758c4aa203ab..1d74aeb1462e 100644
--- a/drivers/tty/serial/8250/8250_acorn.c
+++ b/drivers/tty/serial/8250/8250_acorn.c
@@ -60,16 +60,8 @@ serial_card_probe(struct expansion_card *ec, const struct ecard_id *id)
 	ecard_set_drvdata(ec, info);
 
 	memset(&uart, 0, sizeof(struct uart_8250_port));
-	uart.port.irq	= ec->irq;
-	uart.port.flags	= UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
-	uart.port.uartclk	= type->uartclk;
-	uart.port.iotype	= UPIO_MEM;
-	uart.port.regshift	= 2;
-	uart.port.dev	= &ec->dev;
 
 	for (i = 0; i < info->num_ports; i++) {
-		uart.port.membase = info->vaddr + type->offset[i];
-		uart.port.mapbase = bus_addr + type->offset[i];
 
 		info->ports[i] = serial8250_register_8250_port(&uart);
 	}
diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c
index 26fc0464f1cc..24cfd8fbec4e 100644
--- a/drivers/tty/serial/8250/8250_aspeed_vuart.c
+++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c
@@ -438,25 +438,11 @@ static int aspeed_vuart_probe(struct platform_device *pdev)
 		return -EINVAL;
 
 	memset(&port, 0, sizeof(port));
-	port.port.private_data = vuart;
-	port.port.mapbase = res->start;
-	port.port.mapsize = resource_size(res);
-	port.port.startup = aspeed_vuart_startup;
-	port.port.shutdown = aspeed_vuart_shutdown;
-	port.port.throttle = aspeed_vuart_throttle;
-	port.port.unthrottle = aspeed_vuart_unthrottle;
-	port.port.status = UPSTAT_SYNC_FIFO;
-	port.port.dev = &pdev->dev;
-	port.port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);
-	port.port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP | UPF_FIXED_PORT | UPF_FIXED_TYPE |
-			  UPF_NO_THRE_TEST;
-	port.bugs |= UART_BUG_TXRACE;
 
 	rc = sysfs_create_group(&vuart->dev->kobj, &aspeed_vuart_attr_group);
 	if (rc < 0)
 		return rc;
 
-	rc = uart_read_port_properties(&port.port);
 	if (rc)
 		goto err_sysfs_remove;
 
@@ -468,21 +454,13 @@ static int aspeed_vuart_probe(struct platform_device *pdev)
 			goto err_sysfs_remove;
 		}
 
-		port.port.uartclk = clk_get_rate(vclk);
 	}
 
 	/* If current-speed was set, then try not to change it. */
 	if (of_property_read_u32(np, "current-speed", &prop) == 0)
-		port.port.custom_divisor = port.port.uartclk / (16 * prop);
 
-	port.port.handle_irq = aspeed_vuart_handle_irq;
-	port.port.type = PORT_ASPEED_VUART;
-
-	if (port.port.fifosize)
-		port.capabilities = UART_CAP_FIFO;
 
 	if (of_property_read_bool(np, "auto-flow-control"))
-		port.capabilities |= UART_CAP_AFE;
 
 	rc = serial8250_register_8250_port(&port);
 	if (rc < 0)
diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
index 0609582a62f7..824dbee0d67a 100644
--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
@@ -95,14 +95,6 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	/* initialize data */
-	up.capabilities = UART_CAP_FIFO | UART_CAP_MINI;
-	up.port.dev = &pdev->dev;
-	up.port.type = PORT_16550;
-	up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_SKIP_TEST | UPF_IOREMAP;
-	up.port.rs485_config = serial8250_em485_config;
-	up.port.rs485_supported = serial8250_em485_supported;
-	up.rs485_start_tx = bcm2835aux_rs485_start_tx;
-	up.rs485_stop_tx = bcm2835aux_rs485_stop_tx;
 
 	/* initialize cached copy with power-on reset value */
 	data->cntl = BCM2835_AUX_UART_CNTL_RXEN | BCM2835_AUX_UART_CNTL_TXEN;
@@ -121,8 +113,6 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	up.port.mapbase = res->start;
-	up.port.mapsize = resource_size(res);
 
 	bcm2835_swnode = device_get_match_data(&pdev->dev);
 	if (bcm2835_swnode) {
@@ -131,12 +121,9 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
 			return ret;
 	}
 
-	ret = uart_read_port_properties(&up.port);
 	if (ret)
 		goto rm_swnode;
 
-	up.port.regshift = 2;
-	up.port.fifosize = 8;
 
 	/* enable the clock as a last step */
 	ret = clk_prepare_enable(data->clk);
@@ -147,14 +134,12 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
 
 	uartclk = clk_get_rate(data->clk);
 	if (uartclk)
-		up.port.uartclk = uartclk;
 
 	/* the HW-clock divider for bcm2835aux is 8,
 	 * but 8250 expects a divider of 16,
 	 * so we have to multiply the actual clock by 2
 	 * to get identical baudrates.
 	 */
-	up.port.uartclk *= 2;
 
 	/* register the port */
 	ret = serial8250_register_8250_port(&up);
diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
index 742004d63c6f..3b9504ec440f 100644
--- a/drivers/tty/serial/8250/8250_bcm7271.c
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -1025,20 +1025,11 @@ static int brcmuart_probe(struct platform_device *pdev)
 	dev_dbg(dev, "DMA is %senabled\n", priv->dma_enabled ? "" : "not ");
 
 	memset(&up, 0, sizeof(up));
-	up.port.type = PORT_BCM7271;
-	up.port.dev = dev;
-	up.port.mapbase = mapbase;
-	up.port.membase = membase;
-	up.port.handle_irq = brcmuart_handle_irq;
-	up.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	up.port.private_data = priv;
 
 	ret = uart_read_port_properties(&up.port);
 	if (ret)
 		goto release_dma;
 
-	up.port.regshift = 2;
-	up.port.iotype = device_is_big_endian(dev) ? UPIO_MEM32BE : UPIO_MEM32;
 
 	/* See if a Baud clock has been specified */
 	baud_mux_clk = devm_clk_get_optional_enabled(dev, "sw_baud");
@@ -1050,7 +1041,6 @@ static int brcmuart_probe(struct platform_device *pdev)
 
 		priv->baud_mux_clk = baud_mux_clk;
 		init_real_clk_rates(dev, priv);
-		up.port.uartclk = priv->default_mux_rate;
 	} else {
 		dev_dbg(dev, "BAUD MUX clock not specified\n");
 	}
@@ -1058,11 +1048,6 @@ static int brcmuart_probe(struct platform_device *pdev)
 	/* setup HR timer */
 	hrtimer_setup(&priv->hrt, brcmuart_hrtimer_func, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 
-	up.port.shutdown = brcmuart_shutdown;
-	up.port.startup = brcmuart_startup;
-	up.port.throttle = brcmuart_throttle;
-	up.port.unthrottle = brcmuart_unthrottle;
-	up.port.set_termios = brcmstb_set_termios;
 
 	if (priv->dma_enabled) {
 		priv->rx_size = RX_BUF_SIZE * RX_BUFS_COUNT;
diff --git a/drivers/tty/serial/8250/8250_dfl.c b/drivers/tty/serial/8250/8250_dfl.c
index f46cb8981cb1..cd5451cb8940 100644
--- a/drivers/tty/serial/8250/8250_dfl.c
+++ b/drivers/tty/serial/8250/8250_dfl.c
@@ -60,23 +60,18 @@ static int dfl_uart_get_params(struct dfl_device *dfl_dev, struct uart_8250_port
 	if (ret)
 		return dev_err_probe(dev, ret, "missing CLK_FRQ param\n");
 
-	uart->port.uartclk = clk_freq;
-
 	ret = dfh_get_u64_param_val(dfl_dev, DFHv1_PARAM_ID_FIFO_LEN, &fifo_len);
 	if (ret)
 		return dev_err_probe(dev, ret, "missing FIFO_LEN param\n");
 
 	switch (fifo_len) {
 	case 32:
-		uart->port.type = PORT_ALTR_16550_F32;
 		break;
 
 	case 64:
-		uart->port.type = PORT_ALTR_16550_F64;
 		break;
 
 	case 128:
-		uart->port.type = PORT_ALTR_16550_F128;
 		break;
 
 	default:
@@ -87,15 +82,12 @@ static int dfl_uart_get_params(struct dfl_device *dfl_dev, struct uart_8250_port
 	if (ret)
 		return dev_err_probe(dev, ret, "missing REG_LAYOUT param\n");
 
-	uart->port.regshift = FIELD_GET(DFHv1_PARAM_REG_LAYOUT_SHIFT, reg_layout);
 	reg_width = FIELD_GET(DFHv1_PARAM_REG_LAYOUT_WIDTH, reg_layout);
 	switch (reg_width) {
 	case 4:
-		uart->port.iotype = UPIO_MEM32;
 		break;
 
 	case 2:
-		uart->port.iotype = UPIO_MEM16;
 		break;
 
 	default:
@@ -113,17 +105,11 @@ static int dfl_uart_probe(struct dfl_device *dfl_dev)
 	struct dfl_uart *dfluart;
 	int ret;
 
-	uart.port.flags = UPF_IOREMAP;
-	uart.port.mapbase = dfl_dev->mmio_res.start;
-	uart.port.mapsize = resource_size(&dfl_dev->mmio_res);
-	uart.port.dev = dev;
-
 	ret = dfl_uart_get_params(dfl_dev, &uart);
 	if (ret < 0)
 		return dev_err_probe(dev, ret, "failed uart feature walk\n");
 
 	if (dfl_dev->num_irqs == 1)
-		uart.port.irq = dfl_dev->irqs[0];
 
 	dfluart = devm_kzalloc(dev, sizeof(*dfluart), GFP_KERNEL);
 	if (!dfluart)
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index a53ba04d9770..fa526dd3298b 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -496,18 +496,12 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 
 #ifdef CONFIG_64BIT
 	if (quirks & DW_UART_QUIRK_OCTEON) {
-		p->serial_in = dw8250_serial_inq;
-		p->serial_out = dw8250_serial_outq;
-		p->flags = UPF_SKIP_TEST | UPF_SHARE_IRQ | UPF_FIXED_TYPE;
-		p->type = PORT_OCTEON;
 		data->skip_autocfg = true;
 	}
 #endif
 
 	if (quirks & DW_UART_QUIRK_ARMADA_38X)
-		p->serial_out = dw8250_serial_out38x;
 	if (quirks & DW_UART_QUIRK_SKIP_SET_RATE)
-		p->set_termios = dw8250_do_set_termios;
 	if (quirks & DW_UART_QUIRK_IS_DMA_FC) {
 		data->data.dma.txconf.device_fc = 1;
 		data->data.dma.rxconf.device_fc = 1;
@@ -515,9 +509,6 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 		data->data.dma.prepare_rx_dma = dw8250_prepare_rx_dma;
 	}
 	if (quirks & DW_UART_QUIRK_APMC0D08) {
-		p->iotype = UPIO_MEM32;
-		p->regshift = 2;
-		p->serial_in = dw8250_serial_in32;
 		data->uart_16550_compatible = true;
 	}
 }
@@ -540,28 +531,13 @@ static int dw8250_probe(struct platform_device *pdev)
 	if (!regs)
 		return dev_err_probe(dev, -EINVAL, "no registers defined\n");
 
-	spin_lock_init(&p->lock);
-	p->pm		= dw8250_do_pm;
-	p->type		= PORT_8250;
-	p->flags	= UPF_FIXED_PORT;
-	p->dev		= dev;
-	p->set_ldisc	= dw8250_set_ldisc;
-	p->set_termios	= dw8250_set_termios;
-
 	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
 
-	p->private_data = &data->data;
-
-	p->mapbase = regs->start;
-	p->mapsize = resource_size(regs);
-
-	p->membase = devm_ioremap(dev, p->mapbase, p->mapsize);
 	if (!p->membase)
 		return -ENOMEM;
 
-	err = uart_read_port_properties(p);
 	/* no interrupt -> fall back to polling */
 	if (err == -ENXIO)
 		err = 0;
@@ -570,16 +546,10 @@ static int dw8250_probe(struct platform_device *pdev)
 
 	switch (p->iotype) {
 	case UPIO_MEM:
-		p->serial_in = dw8250_serial_in;
-		p->serial_out = dw8250_serial_out;
 		break;
 	case UPIO_MEM32:
-		p->serial_in = dw8250_serial_in32;
-		p->serial_out = dw8250_serial_out32;
 		break;
 	case UPIO_MEM32BE:
-		p->serial_in = dw8250_serial_in32be;
-		p->serial_out = dw8250_serial_out32be;
 		break;
 	default:
 		return -ENODEV;
@@ -621,7 +591,6 @@ static int dw8250_probe(struct platform_device *pdev)
 	data->clk_notifier.notifier_call = dw8250_clk_notifier_cb;
 
 	if (data->clk)
-		p->uartclk = clk_get_rate(data->clk);
 
 	/* If no clock rate is defined, fail. */
 	if (!p->uartclk)
@@ -662,7 +631,6 @@ static int dw8250_probe(struct platform_device *pdev)
 	if (p->fifosize) {
 		data->data.dma.rxconf.src_maxburst = p->fifosize / 4;
 		data->data.dma.txconf.dst_maxburst = p->fifosize / 4;
-		up->dma = &data->data.dma;
 	}
 
 	data->data.line = serial8250_register_8250_port(up);
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c
index b055d89cfb39..71ee94d0545c 100644
--- a/drivers/tty/serial/8250/8250_dwlib.c
+++ b/drivers/tty/serial/8250/8250_dwlib.c
@@ -247,16 +247,8 @@ void dw8250_setup_port(struct uart_port *p)
 
 	pd->hw_rs485_support = dw8250_detect_rs485_hw(p);
 	if (pd->hw_rs485_support) {
-		p->rs485_config = dw8250_rs485_config;
-		up->lsr_save_mask = LSR_SAVE_FLAGS | DW_UART_LSR_ADDR_RCVD;
-		p->rs485_supported = dw8250_rs485_supported;
 	} else {
-		p->rs485_config = serial8250_em485_config;
-		p->rs485_supported = serial8250_em485_supported;
-		up->rs485_start_tx = serial8250_em485_start_tx;
-		up->rs485_stop_tx = serial8250_em485_stop_tx;
 	}
-	up->capabilities |= UART_CAP_NOTEMT;
 
 	/* Preserve value written by firmware or bootloader  */
 	old_dlf = dw8250_readl_ext(p, DW_UART_DLF);
@@ -266,8 +258,6 @@ void dw8250_setup_port(struct uart_port *p)
 
 	if (reg) {
 		pd->dlf_size = fls(reg);
-		p->get_divisor = dw8250_get_divisor;
-		p->set_divisor = dw8250_set_divisor;
 	}
 
 	reg = dw8250_readl_ext(p, DW_UART_UCV);
@@ -285,16 +275,12 @@ void dw8250_setup_port(struct uart_port *p)
 
 	/* Select the type based on FIFO */
 	if (reg & DW_UART_CPR_FIFO_MODE) {
-		p->type = PORT_16550A;
-		p->flags |= UPF_FIXED_TYPE;
-		p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
-		up->capabilities = UART_CAP_FIFO | UART_CAP_NOTEMT;
 	}
 
 	if (reg & DW_UART_CPR_AFCE_MODE)
-		up->capabilities |= UART_CAP_AFE;
+	;
 
 	if (reg & DW_UART_CPR_SIR_MODE)
-		up->capabilities |= UART_CAP_IRDA;
+	;
 }
 EXPORT_SYMBOL_GPL(dw8250_setup_port);
diff --git a/drivers/tty/serial/8250/8250_em.c b/drivers/tty/serial/8250/8250_em.c
index e90c71494944..d8cba8ea8160 100644
--- a/drivers/tty/serial/8250/8250_em.c
+++ b/drivers/tty/serial/8250/8250_em.c
@@ -176,20 +176,6 @@ static int serial8250_em_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(sclk), "unable to get clock\n");
 
 	memset(&up, 0, sizeof(up));
-	up.port.mapbase = regs->start;
-	up.port.irq = irq;
-	up.port.type = PORT_16750;
-	up.port.flags = UPF_FIXED_PORT | UPF_IOREMAP | UPF_FIXED_TYPE;
-	up.port.dev = dev;
-	up.port.private_data = priv;
-
-	up.port.uartclk = clk_get_rate(sclk);
-
-	up.port.iotype = UPIO_MEM32;
-	up.port.serial_in = serial8250_em_serial_in;
-	up.port.serial_out = serial8250_em_serial_out;
-	up.dl_read = serial8250_em_serial_dl_read;
-	up.dl_write = serial8250_em_serial_dl_write;
 
 	ret = serial8250_register_8250_port(&up);
 	if (ret < 0)
diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
index 04a0cbab02c2..f7772b2d844d 100644
--- a/drivers/tty/serial/8250/8250_exar.c
+++ b/drivers/tty/serial/8250/8250_exar.c
@@ -516,19 +516,9 @@ static int default_setup(struct exar8250 *priv, struct pci_dev *pcidev,
 	 */
 	status = readb(port->port.membase + UART_EXAR_DVID);
 	if (status == 0x82 || status == 0x84 || status == 0x88) {
-		port->port.type = PORT_XR17V35X;
-
-		port->port.get_divisor = xr17v35x_get_divisor;
-		port->port.set_divisor = xr17v35x_set_divisor;
-
-		port->port.startup = xr17v35x_startup;
 	} else {
-		port->port.type = PORT_XR17D15X;
 	}
 
-	port->port.pm = exar_pm;
-	port->port.shutdown = exar_shutdown;
-
 	return 0;
 }
 
@@ -541,8 +531,6 @@ pci_fastcom335_setup(struct exar8250 *priv, struct pci_dev *pcidev,
 	u8 __iomem *p;
 	int err;
 
-	port->port.uartclk = baud * 16;
-
 	err = default_setup(priv, pcidev, idx, offset, port);
 	if (err)
 		return err;
@@ -828,17 +816,10 @@ static int cti_port_setup_common(struct exar8250 *priv,
 {
 	int ret;
 
-	port->port.port_id = idx;
-	port->port.uartclk = priv->osc_freq;
-
 	ret = serial8250_pci_setup_port(pcidev, port, 0, offset, 0);
 	if (ret)
 		return ret;
 
-	port->port.private_data = (void *)priv;
-	port->port.pm = exar_pm;
-	port->port.shutdown = exar_shutdown;
-
 	return 0;
 }
 
@@ -1062,7 +1043,6 @@ static int cti_port_setup_xr17c15x(struct exar8250 *priv,
 	port_type = cti_get_port_type_xr17c15x_xr17v25x(priv, pcidev, idx);
 
 	offset = idx * UART_EXAR_XR17C15X_PORT_OFFSET;
-	port->port.type = PORT_XR17D15X;
 
 	if (CTI_PORT_TYPE_RS485(port_type)) {
 		switch (pcidev->subsystem_device) {
@@ -1078,15 +1058,12 @@ static int cti_port_setup_xr17c15x(struct exar8250 *priv,
 		case PCI_SUBDEVICE_ID_CONNECT_TECH_PCI_UART_4_4_XPRS_OPTO:
 		case PCI_SUBDEVICE_ID_CONNECT_TECH_PCI_UART_8_XPRS_LP:
 		case PCI_SUBDEVICE_ID_CONNECT_TECH_PCI_UART_8_XPRS_LP_485:
-			port->port.rs485_config = cti_rs485_config_mpio_tristate;
 			break;
 		// Otherwise auto or no power on 485 tri-state support
 		default:
-			port->port.rs485_config = generic_rs485_config;
 			break;
 		}
 
-		port->port.rs485_supported = generic_rs485_supported;
 	}
 
 	return cti_port_setup_common(priv, pcidev, idx, offset, port);
@@ -1481,9 +1458,6 @@ exar_pci_probe(struct pci_dev *pcidev, const struct pci_device_id *ent)
 		return rc;
 
 	memset(&uart, 0, sizeof(uart));
-	uart.port.flags = UPF_SHARE_IRQ | UPF_EXAR_EFR | UPF_FIXED_TYPE | UPF_FIXED_PORT;
-	uart.port.irq = pci_irq_vector(pcidev, 0);
-	uart.port.dev = &pcidev->dev;
 
 	/* Clear interrupts */
 	exar_misc_clear(priv);
diff --git a/drivers/tty/serial/8250/8250_fsl.c b/drivers/tty/serial/8250/8250_fsl.c
index 649ae5c8304d..234a25f561b5 100644
--- a/drivers/tty/serial/8250/8250_fsl.c
+++ b/drivers/tty/serial/8250/8250_fsl.c
@@ -129,22 +129,6 @@ static int fsl8250_acpi_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	spin_lock_init(&port8250.port.lock);
-
-	port8250.port.mapbase           = regs->start;
-	port8250.port.irq               = irq;
-	port8250.port.handle_irq        = fsl8250_handle_irq;
-	port8250.port.type              = PORT_16550A;
-	port8250.port.flags             = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF
-						| UPF_FIXED_PORT | UPF_IOREMAP
-						| UPF_FIXED_TYPE;
-	port8250.port.dev               = dev;
-	port8250.port.mapsize           = resource_size(regs);
-	port8250.port.iotype            = UPIO_MEM;
-	port8250.port.irqflags          = IRQF_SHARED;
-
-	port8250.port.membase = devm_ioremap(dev,  port8250.port.mapbase,
-							port8250.port.mapsize);
 	if (!port8250.port.membase)
 		return -ENOMEM;
 
diff --git a/drivers/tty/serial/8250/8250_hp300.c b/drivers/tty/serial/8250/8250_hp300.c
index 3012ea03d22c..5b9050a31ce8 100644
--- a/drivers/tty/serial/8250/8250_hp300.c
+++ b/drivers/tty/serial/8250/8250_hp300.c
@@ -249,15 +249,6 @@ static int __init hp300_8250_init(void)
 		base = (FRODO_BASE + FRODO_APCI_OFFSET(i));
 
 		/* Memory mapped I/O */
-		uart.port.iotype = UPIO_MEM;
-		uart.port.flags = UPF_SKIP_TEST | UPF_SHARE_IRQ
-				| UPF_BOOT_AUTOCONF;
-		/* XXX - no interrupt support yet */
-		uart.port.irq = 0;
-		uart.port.uartclk = HPAPCI_BAUD_BASE * 16;
-		uart.port.mapbase = base;
-		uart.port.membase = (char *)(base + DIO_VIRADDRBASE);
-		uart.port.regshift = 2;
 
 		line = serial8250_register_8250_port(&uart);
 
diff --git a/drivers/tty/serial/8250/8250_ingenic.c b/drivers/tty/serial/8250/8250_ingenic.c
index 94542fc143c2..39d156ed38fc 100644
--- a/drivers/tty/serial/8250/8250_ingenic.c
+++ b/drivers/tty/serial/8250/8250_ingenic.c
@@ -252,25 +252,9 @@ static int ingenic_uart_probe(struct platform_device *pdev)
 	if (!data)
 		return -ENOMEM;
 
-	spin_lock_init(&uart.port.lock);
-	uart.port.type = PORT_16550A;
-	uart.port.flags = UPF_SKIP_TEST | UPF_IOREMAP | UPF_FIXED_TYPE;
-	uart.port.mapbase = regs->start;
-	uart.port.serial_out = ingenic_uart_serial_out;
-	uart.port.serial_in = ingenic_uart_serial_in;
-	uart.port.dev = &pdev->dev;
-	uart.tx_loadsz = cdata->tx_loadsz;
-	uart.capabilities = UART_CAP_FIFO | UART_CAP_RTOIE;
-
-	err = uart_read_port_properties(&uart.port);
 	if (err)
 		return err;
 
-	uart.port.regshift = 2;
-	uart.port.fifosize = cdata->fifosize;
-
-	uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
-					 resource_size(regs));
 	if (!uart.port.membase)
 		return -ENOMEM;
 
@@ -295,7 +279,6 @@ static int ingenic_uart_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "could not enable baud clock: %d\n", err);
 		goto out_disable_moduleclk;
 	}
-	uart.port.uartclk = clk_get_rate(data->clk_baud);
 
 	data->line = serial8250_register_8250_port(&uart);
 	if (data->line < 0) {
diff --git a/drivers/tty/serial/8250/8250_ioc3.c b/drivers/tty/serial/8250/8250_ioc3.c
index 28e28076782b..51a9555307fa 100644
--- a/drivers/tty/serial/8250/8250_ioc3.c
+++ b/drivers/tty/serial/8250/8250_ioc3.c
@@ -57,16 +57,6 @@ static int serial8250_ioc3_probe(struct platform_device *pdev)
 
 	/* Register serial ports with 8250.c */
 	memset(&up, 0, sizeof(struct uart_8250_port));
-	up.port.iotype = UPIO_MEM;
-	up.port.uartclk = IOC3_UARTCLK;
-	up.port.type = PORT_16550A;
-	up.port.irq = irq;
-	up.port.flags = (UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ);
-	up.port.dev = &pdev->dev;
-	up.port.membase = membase;
-	up.port.mapbase = r->start;
-	up.port.serial_in = ioc3_serial_in;
-	up.port.serial_out = ioc3_serial_out;
 	line = serial8250_register_8250_port(&up);
 	if (line < 0)
 		return line;
diff --git a/drivers/tty/serial/8250/8250_lpc18xx.c b/drivers/tty/serial/8250/8250_lpc18xx.c
index 6c0489c9c253..8670c40efaf5 100644
--- a/drivers/tty/serial/8250/8250_lpc18xx.c
+++ b/drivers/tty/serial/8250/8250_lpc18xx.c
@@ -102,8 +102,6 @@ static int lpc18xx_serial_probe(struct platform_device *pdev)
 
 	memset(&uart, 0, sizeof(uart));
 
-	uart.port.membase = devm_ioremap(&pdev->dev, res->start,
-					 resource_size(res));
 	if (!uart.port.membase)
 		return -ENOMEM;
 
@@ -138,28 +136,10 @@ static int lpc18xx_serial_probe(struct platform_device *pdev)
 	data->dma.rx_param = data;
 	data->dma.tx_param = data;
 
-	spin_lock_init(&uart.port.lock);
-	uart.port.dev = &pdev->dev;
-	uart.port.mapbase = res->start;
-	uart.port.type = PORT_16550A;
-	uart.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_SKIP_TEST;
-	uart.port.uartclk = clk_get_rate(data->clk_uart);
-	uart.port.private_data = data;
-	uart.port.rs485_config = lpc18xx_rs485_config;
-	uart.port.rs485_supported = lpc18xx_rs485_supported;
-	uart.port.serial_out = lpc18xx_uart_serial_out;
-
 	ret = uart_read_port_properties(&uart.port);
 	if (ret)
 		goto dis_uart_clk;
 
-	uart.port.iotype = UPIO_MEM32;
-	uart.port.regshift = 2;
-
-	uart.dma = &data->dma;
-	uart.dma->rxconf.src_maxburst = 1;
-	uart.dma->txconf.dst_maxburst = 1;
-
 	ret = serial8250_register_8250_port(&uart);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "unable to register 8250 port\n");
diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index 776ec1ef29d6..0e3379f9008e 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -299,8 +299,6 @@ static int lpss8250_dma_setup(struct lpss8250 *lpss, struct uart_8250_port *port
 	dma->rx_param = rx_param;
 	dma->tx_param = tx_param;
 
-	port->dma = dma;
-
 out_configuration_only:
 	dma->rxconf.src_maxburst = lpss->dma_maxburst;
 	dma->txconf.dst_maxburst = lpss->dma_maxburst;
@@ -332,17 +330,6 @@ static int lpss8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 	memset(&uart, 0, sizeof(struct uart_8250_port));
 
-	uart.port.dev = &pdev->dev;
-	uart.port.irq = pci_irq_vector(pdev, 0);
-	uart.port.private_data = &lpss->data;
-	uart.port.type = PORT_16550A;
-	uart.port.iotype = UPIO_MEM32;
-	uart.port.regshift = 2;
-	uart.port.uartclk = lpss->board->base_baud * 16;
-	uart.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	uart.capabilities = UART_CAP_FIFO | UART_CAP_AFE;
-	uart.port.mapbase = pci_resource_start(pdev, 0);
-	uart.port.membase = pcim_iomap(pdev, 0, 0);
 	if (!uart.port.membase)
 		return -ENOMEM;
 
diff --git a/drivers/tty/serial/8250/8250_men_mcb.c b/drivers/tty/serial/8250/8250_men_mcb.c
index f7111337d50f..cb173ef42afa 100644
--- a/drivers/tty/serial/8250/8250_men_mcb.c
+++ b/drivers/tty/serial/8250/8250_men_mcb.c
@@ -209,18 +209,6 @@ static int serial_8250_men_mcb_probe(struct mcb_device *mdev,
 
 	for (i = 0; i < data->num_ports; i++) {
 		memset(&uart, 0, sizeof(struct uart_8250_port));
-		spin_lock_init(&uart.port.lock);
-
-		uart.port.flags = UPF_SKIP_TEST |
-				  UPF_SHARE_IRQ |
-				  UPF_BOOT_AUTOCONF |
-				  UPF_IOREMAP;
-		uart.port.iotype = UPIO_MEM;
-		uart.port.uartclk = men_lookup_uartclk(mdev);
-		uart.port.irq = mcb_get_irq(mdev);
-		uart.port.mapbase = (unsigned long) mem->start
-					    + data->offset[i];
-		uart.port.dev = &mdev->dev;
 
 		/* ok, register the port */
 		res = serial8250_register_8250_port(&uart);
diff --git a/drivers/tty/serial/8250/8250_mid.c b/drivers/tty/serial/8250/8250_mid.c
index 8ec03863606e..d0765737f7f0 100644
--- a/drivers/tty/serial/8250/8250_mid.c
+++ b/drivers/tty/serial/8250/8250_mid.c
@@ -124,7 +124,6 @@ static int tng_setup(struct mid8250 *mid, struct uart_port *p)
 	mid->dma_index = index;
 	mid->dma_dev = pci_get_slot(pdev->bus, PCI_DEVFN(5, 0));
 
-	p->handle_irq = tng_handle_irq;
 	return 0;
 }
 
@@ -176,8 +175,6 @@ static int dnv_setup(struct mid8250 *mid, struct uart_port *p)
 	if (ret < 0)
 		return ret;
 
-	p->irq = pci_irq_vector(pdev, 0);
-
 	chip->dev = &pdev->dev;
 	chip->irq = pci_irq_vector(pdev, 0);
 	chip->regs = p->membase;
@@ -191,7 +188,6 @@ static int dnv_setup(struct mid8250 *mid, struct uart_port *p)
 
 	mid->dma_dev = pdev;
 
-	p->handle_irq = dnv_handle_irq;
 	return 0;
 }
 
@@ -281,7 +277,6 @@ static int mid8250_dma_setup(struct mid8250 *mid, struct uart_8250_port *port)
 	dma->rx_param = rx_param;
 	dma->tx_param = tx_param;
 
-	port->dma = dma;
 	return 0;
 }
 
@@ -303,17 +298,6 @@ static int mid8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 
 	memset(&uart, 0, sizeof(struct uart_8250_port));
 
-	uart.port.dev = &pdev->dev;
-	uart.port.irq = pdev->irq;
-	uart.port.private_data = mid;
-	uart.port.type = PORT_16750;
-	uart.port.iotype = UPIO_MEM;
-	uart.port.uartclk = mid->board->base_baud * 16;
-	uart.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	uart.port.set_termios = mid8250_set_termios;
-
-	uart.port.mapbase = pci_resource_start(pdev, mid->board->bar);
-	uart.port.membase = pcim_iomap(pdev, mid->board->bar, 0);
 	if (!uart.port.membase)
 		return -ENOMEM;
 
diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index b44de2ed7413..c04c07c79a74 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -530,8 +530,6 @@ static int mtk8250_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	uart.port.membase = devm_ioremap(&pdev->dev, regs->start,
-					 resource_size(regs));
 	if (!uart.port.membase)
 		return -ENOMEM;
 
@@ -549,22 +547,9 @@ static int mtk8250_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	spin_lock_init(&uart.port.lock);
-	uart.port.mapbase = regs->start;
-	uart.port.irq = irq;
-	uart.port.pm = mtk8250_do_pm;
-	uart.port.type = PORT_16550;
-	uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT;
-	uart.port.dev = &pdev->dev;
-	uart.port.iotype = UPIO_MEM32;
-	uart.port.regshift = 2;
-	uart.port.private_data = data;
-	uart.port.shutdown = mtk8250_shutdown;
-	uart.port.startup = mtk8250_startup;
-	uart.port.set_termios = mtk8250_set_termios;
-	uart.port.uartclk = clk_get_rate(data->uart_clk);
 #ifdef CONFIG_SERIAL_8250_DMA
 	if (data->dma)
-		uart.dma = data->dma;
+	;
 #endif
 
 	/* Disable Rate Fix function */
diff --git a/drivers/tty/serial/8250/8250_ni.c b/drivers/tty/serial/8250/8250_ni.c
index cb5b42b3609c..4fa89a67d117 100644
--- a/drivers/tty/serial/8250/8250_ni.c
+++ b/drivers/tty/serial/8250/8250_ni.c
@@ -196,13 +196,10 @@ static const struct serial_rs485 ni16550_rs485_supported = {
 
 static void ni16550_rs485_setup(struct uart_port *port)
 {
-	port->rs485_config = ni16550_rs485_config;
-	port->rs485_supported = ni16550_rs485_supported;
 	/*
 	 * The hardware comes up by default in 2-wire auto mode and we
 	 * set the flags to represent that
 	 */
-	port->rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
 }
 
 static int ni16550_port_startup(struct uart_port *port)
@@ -300,15 +297,9 @@ static int ni16550_probe(struct platform_device *pdev)
 		return ret;
 
 	/* early setup so that serial_in()/serial_out() work */
-	serial8250_set_defaults(uart);
 
 	info = device_get_match_data(dev);
 
-	uart->port.dev		= dev;
-	uart->port.flags	= UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	uart->port.startup	= ni16550_port_startup;
-	uart->port.shutdown	= ni16550_port_shutdown;
-
 	/*
 	 * Hardware instantiation of FIFO sizes are held in registers.
 	 */
@@ -318,18 +309,12 @@ static int ni16550_probe(struct platform_device *pdev)
 	dev_dbg(dev, "NI 16550 has TX FIFO size %u, RX FIFO size %u\n",
 		txfifosz, rxfifosz);
 
-	uart->port.type		= PORT_16550A;
-	uart->port.fifosize	= txfifosz;
-	uart->tx_loadsz		= txfifosz;
-	uart->fcr		= UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10;
-	uart->capabilities	= UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR;
 
 	/*
 	 * Declaration of the base clock frequency can come from one of:
 	 * - static declaration in this driver (for older ACPI IDs)
 	 * - a "clock-frequency" ACPI
 	 */
-	uart->port.uartclk = info->uartclk;
 
 	ret = uart_read_port_properties(&uart->port);
 	if (ret)
@@ -338,7 +323,7 @@ static int ni16550_probe(struct platform_device *pdev)
 	if (!uart->port.uartclk) {
 		data->clk = devm_clk_get_enabled(dev, NULL);
 		if (!IS_ERR(data->clk))
-			uart->port.uartclk = clk_get_rate(data->clk);
+			;
 	}
 
 	if (!uart->port.uartclk)
@@ -347,7 +332,6 @@ static int ni16550_probe(struct platform_device *pdev)
 	prescaler = info->prescaler;
 	device_property_read_u32(dev, "clock-prescaler", &prescaler);
 	if (prescaler) {
-		uart->port.set_mctrl = ni16550_set_mctrl;
 		ni16550_config_prescaler(uart, (u8)prescaler);
 	}
 
diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index d178b6c54ea1..ff518b374143 100644
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -56,8 +56,6 @@ static unsigned int npcm_get_divisor(struct uart_port *port, unsigned int baud,
 
 static int npcm_setup(struct uart_port *port)
 {
-	port->get_divisor = npcm_get_divisor;
-	port->startup = npcm_startup;
 	return 0;
 }
 
@@ -106,16 +104,8 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 		goto err_pmruntime;
 	}
 
-	port->dev = &ofdev->dev;
-	port->flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	spin_lock_init(&port->lock);
-
 	if (resource_type(&resource) == IORESOURCE_IO) {
-		port->iobase = resource.start;
 	} else {
-		port->mapbase = resource.start;
-		port->mapsize = resource_size(&resource);
-		port->flags |= UPF_IOREMAP;
 	}
 
 	ret = uart_read_and_validate_port_properties(port);
@@ -140,15 +130,12 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 		}
 
 		info->bus_clk = bus_clk;
-		port->uartclk = clk_get_rate(info->clk);
 	}
 	/* If current-speed was set, then try not to change it. */
 	if (of_property_read_u32(np, "current-speed", &spd) == 0)
-		port->custom_divisor = port->uartclk / (16 * spd);
 
 	/* Compatibility with the deprecated pxa driver and 8250_pxa drivers. */
 	if (of_device_is_compatible(np, "mrvl,mmp-uart"))
-		port->regshift = 2;
 
 	info->rst = devm_reset_control_get_optional_shared(&ofdev->dev, NULL);
 	if (IS_ERR(info->rst)) {
@@ -160,12 +147,6 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 	if (ret)
 		goto err_pmruntime;
 
-	port->type = type;
-	port->rs485_config = serial8250_em485_config;
-	port->rs485_supported = serial8250_em485_supported;
-	up->rs485_start_tx = serial8250_em485_start_tx;
-	up->rs485_stop_tx = serial8250_em485_stop_tx;
-
 	switch (type) {
 	case PORT_RT2880:
 		ret = rt288x_setup(port);
@@ -184,8 +165,6 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 	if (IS_REACHABLE(CONFIG_SERIAL_8250_FSL) &&
 	    (of_device_is_compatible(np, "fsl,ns16550") ||
 	     of_device_is_compatible(np, "fsl,16550-FIFO64"))) {
-		port->handle_irq = fsl8250_handle_irq;
-		port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);
 	}
 
 	return 0;
@@ -226,22 +205,19 @@ static int of_platform_serial_probe(struct platform_device *ofdev)
 	if (ret)
 		goto err_free;
 
-	if (port8250.port.fifosize)
-		port8250.capabilities = UART_CAP_FIFO;
-
 	/* Check for TX FIFO threshold & set tx_loadsz */
 	if ((of_property_read_u32(ofdev->dev.of_node, "tx-threshold",
 				  &tx_threshold) == 0) &&
 	    (tx_threshold < port8250.port.fifosize))
-		port8250.tx_loadsz = port8250.port.fifosize - tx_threshold;
+		;
 
 	if (of_property_read_bool(ofdev->dev.of_node, "auto-flow-control"))
-		port8250.capabilities |= UART_CAP_AFE;
+		;
 
 	if (of_property_read_u32(ofdev->dev.of_node,
 			"overrun-throttle-ms",
 			&port8250.overrun_backoff_time_ms) != 0)
-		port8250.overrun_backoff_time_ms = 0;
+		;
 
 	ret = serial8250_register_8250_port(&port8250);
 	if (ret < 0)
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 6707f55bdbe7..c90681ce094a 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -1438,9 +1438,6 @@ static int omap8250_probe(struct platform_device *pdev)
 		return -ENODEV;
 
 	memset(&up, 0, sizeof(up));
-	up.port.dev = &pdev->dev;
-	up.port.mapbase = regs->start;
-	up.port.membase = membase;
 	/*
 	 * It claims to be 16C750 compatible however it is a little different.
 	 * It has EFR and has no FCR7_64byte bit. The AFE (which it claims to
@@ -1449,12 +1446,6 @@ static int omap8250_probe(struct platform_device *pdev)
 	 * we don't need our own type since we don't use 8250's set_termios()
 	 * or pm callback.
 	 */
-	up.port.type = PORT_8250;
-	up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_SOFT_FLOW | UPF_HARD_FLOW;
-	up.port.private_data = priv;
-
-	up.tx_loadsz = 64;
-	up.capabilities = UART_CAP_FIFO;
 #ifdef CONFIG_PM
 	/*
 	 * Runtime PM is mostly transparent. However to do it right we need to a
@@ -1462,28 +1453,12 @@ static int omap8250_probe(struct platform_device *pdev)
 	 * PM is not enabled we don't add that flag and can spare that one extra
 	 * interrupt in the TX path.
 	 */
-	up.capabilities |= UART_CAP_RPM;
 #endif
-	up.port.set_termios = omap_8250_set_termios;
-	up.port.set_mctrl = omap8250_set_mctrl;
-	up.port.pm = omap_8250_pm;
-	up.port.startup = omap_8250_startup;
-	up.port.shutdown = omap_8250_shutdown;
-	up.port.throttle = omap_8250_throttle;
-	up.port.unthrottle = omap_8250_unthrottle;
-	up.port.rs485_config = omap8250_rs485_config;
 	/* same rs485_supported for software emulation and native RS485 */
-	up.port.rs485_supported = serial8250_em485_supported;
-	up.rs485_start_tx = serial8250_em485_start_tx;
-	up.rs485_stop_tx = serial8250_em485_stop_tx;
-	up.port.has_sysrq = IS_ENABLED(CONFIG_SERIAL_8250_CONSOLE);
 
-	ret = uart_read_port_properties(&up.port);
 	if (ret)
 		return ret;
 
-	up.port.regshift = OMAP_UART_REGSHIFT;
-	up.port.fifosize = 64;
 
 	if (!up.port.uartclk) {
 		struct clk *clk;
@@ -1493,20 +1468,17 @@ static int omap8250_probe(struct platform_device *pdev)
 			if (PTR_ERR(clk) == -EPROBE_DEFER)
 				return -EPROBE_DEFER;
 		} else {
-			up.port.uartclk = clk_get_rate(clk);
 		}
 	}
 
 	if (of_property_read_u32(np, "overrun-throttle-ms",
 				 &up.overrun_backoff_time_ms) != 0)
-		up.overrun_backoff_time_ms = 0;
 
 	pdata = of_device_get_match_data(&pdev->dev);
 	if (pdata)
 		priv->habit |= pdata->habit;
 
 	if (!up.port.uartclk) {
-		up.port.uartclk = DEFAULT_CLK_SPEED;
 		dev_warn(&pdev->dev,
 			 "No clock speed specified: using default: %d\n",
 			 DEFAULT_CLK_SPEED);
@@ -1543,7 +1515,6 @@ static int omap8250_probe(struct platform_device *pdev)
 	pm_runtime_get_sync(&pdev->dev);
 
 	omap_serial_fill_features_erratas(&up, priv);
-	up.port.handle_irq = omap8250_no_handle_irq;
 	priv->rx_trigger = RX_TRIGGER;
 	priv->tx_trigger = TX_TRIGGER;
 #ifdef CONFIG_SERIAL_8250_DMA
@@ -1580,7 +1551,6 @@ static int omap8250_probe(struct platform_device *pdev)
 	}
 #endif
 
-	irq_set_status_flags(up.port.irq, IRQ_NOAUTOEN);
 	ret = devm_request_irq(&pdev->dev, up.port.irq, omap8250_irq, 0,
 			       dev_name(&pdev->dev), priv);
 	if (ret < 0)
diff --git a/drivers/tty/serial/8250/8250_parisc.c b/drivers/tty/serial/8250/8250_parisc.c
index 4ba05a98791c..e2cd4ed28758 100644
--- a/drivers/tty/serial/8250/8250_parisc.c
+++ b/drivers/tty/serial/8250/8250_parisc.c
@@ -50,19 +50,11 @@ static int __init serial_init_chip(struct parisc_device *dev)
 		address += 0x800;
 
 	memset(&uart, 0, sizeof(uart));
-	uart.port.iotype	= UPIO_MEM;
 	/* 7.272727MHz on Lasi.  Assumed the same for Dino, Wax and Timi. */
-	uart.port.uartclk	= (dev->id.sversion != 0xad) ?
-					7272727 : 1843200;
-	uart.port.mapbase	= address;
-	uart.port.membase	= ioremap(address, 16);
 	if (!uart.port.membase) {
 		dev_warn(&dev->dev, "Failed to map memory\n");
 		return -ENOMEM;
 	}
-	uart.port.irq	= dev->irq;
-	uart.port.flags	= UPF_BOOT_AUTOCONF;
-	uart.port.dev	= &dev->dev;
 
 	err = serial8250_register_8250_port(&uart);
 	if (err < 0) {
diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 152f914c599d..e614f7b4a2f5 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1542,9 +1542,7 @@ static int pci_quatech_setup(struct serial_private *priv,
 		return serial_8250_warn_need_ioport(priv->dev);
 
 	/* Needed by pci_quatech calls below */
-	port->port.iobase = pci_resource_start(priv->dev, FL_GET_BASE(board->flags));
 	/* Set up the clocking */
-	port->port.uartclk = pci_quatech_clock(port);
 	/* For now just warn about RS422 */
 	if (pci_quatech_rs422(port))
 		pci_warn(priv->dev, "software control of RS422 features not currently supported.\n");
@@ -1580,10 +1578,6 @@ ce4100_serial_setup(struct serial_private *priv,
 	int ret;
 
 	ret = setup_port(priv, port, idx, 0, board->reg_shift);
-	port->port.iotype = UPIO_MEM32;
-	port->port.type = PORT_XSCALE;
-	port->port.flags = (port->port.flags | UPF_FIXED_PORT | UPF_FIXED_TYPE);
-	port->port.regshift = 2;
 
 	return ret;
 }
@@ -1603,8 +1597,6 @@ pci_brcm_trumanage_setup(struct serial_private *priv,
 {
 	int ret = pci_default_setup(priv, board, port, idx);
 
-	port->port.type = PORT_BRCM_TRUMANAGE;
-	port->port.flags = (port->port.flags | UPF_FIXED_PORT | UPF_FIXED_TYPE);
 	return ret;
 }
 
@@ -1668,10 +1660,6 @@ static int pci_fintek_setup(struct serial_private *priv,
 
 	pci_dbg(pdev, "idx=%d iobase=0x%x", idx, iobase);
 
-	port->port.iotype = UPIO_PORT;
-	port->port.iobase = iobase;
-	port->port.rs485_config = pci_fintek_rs485_config;
-	port->port.rs485_supported = pci_fintek_rs485_supported;
 
 	data = devm_kzalloc(&pdev->dev, sizeof(u8), GFP_KERNEL);
 	if (!data)
@@ -1679,7 +1667,6 @@ static int pci_fintek_setup(struct serial_private *priv,
 
 	/* preserve index in PCI configuration space */
 	*data = idx;
-	port->port.private_data = data;
 
 	return 0;
 }
@@ -1776,11 +1763,6 @@ static int pci_fintek_f815xxa_setup(struct serial_private *priv,
 	data->idx = idx;
 	spin_lock_init(&data->lock);
 
-	port->port.private_data = data;
-	port->port.iotype = UPIO_MEM;
-	port->port.flags |= UPF_IOREMAP;
-	port->port.mapbase = pci_resource_start(pdev, 0) + 8 * idx;
-	port->port.serial_out = f815xxa_mem_serial_out;
 
 	return 0;
 }
@@ -1826,7 +1808,6 @@ static int skip_tx_en_setup(struct serial_private *priv,
 			const struct pciserial_board *board,
 			struct uart_8250_port *port, int idx)
 {
-	port->port.quirks |= UPQ_NO_TXEN_TEST;
 	pci_dbg(priv->dev,
 		"serial8250: skipping TxEn test for device [%04x:%04x] subsystem [%04x:%04x]\n",
 		priv->dev->vendor, priv->dev->device,
@@ -1876,9 +1857,6 @@ static int kt_serial_setup(struct serial_private *priv,
 	if (!IS_ENABLED(CONFIG_HAS_IOPORT))
 		return serial_8250_warn_need_ioport(priv->dev);
 
-	port->port.flags |= UPF_BUG_THRE;
-	port->port.serial_in = kt_serial_in;
-	port->port.handle_break = kt_handle_break;
 	return skip_tx_en_setup(priv, board, port, idx);
 }
 
@@ -1978,8 +1956,6 @@ pci_sunix_setup(struct serial_private *priv,
 	int bar;
 	int offset;
 
-	port->port.flags |= UPF_FIXED_TYPE;
-	port->port.type = PORT_SUNIX;
 
 	if (idx < 4) {
 		bar = 0;
@@ -4156,16 +4132,12 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
 	priv->quirk = quirk;
 
 	memset(&uart, 0, sizeof(uart));
-	uart.port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
-	uart.port.uartclk = board->base_baud * 16;
 
 	if (board->flags & FL_NOIRQ) {
-		uart.port.irq = 0;
 	} else {
 		if (pci_match_id(pci_use_msi, dev)) {
 			pci_dbg(dev, "Using MSI(-X) interrupts\n");
 			pci_set_master(dev);
-			uart.port.flags &= ~UPF_SHARE_IRQ;
 			rc = pci_alloc_irq_vectors(dev, 1, 1, PCI_IRQ_ALL_TYPES);
 		} else {
 			pci_dbg(dev, "Using legacy interrupts\n");
@@ -4177,10 +4149,8 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
 			goto err_deinit;
 		}
 
-		uart.port.irq = pci_irq_vector(dev, 0);
 	}
 
-	uart.port.dev = &dev->dev;
 
 	for (i = 0; i < nr_ports; i++) {
 		if (quirk->setup(priv, board, &uart, i))
diff --git a/drivers/tty/serial/8250/8250_pci1xxxx.c b/drivers/tty/serial/8250/8250_pci1xxxx.c
index 4c149db84692..a9ef137ac03c 100644
--- a/drivers/tty/serial/8250/8250_pci1xxxx.c
+++ b/drivers/tty/serial/8250/8250_pci1xxxx.c
@@ -675,8 +675,6 @@ static int pci1xxxx_setup(struct pci_dev *pdev,
 {
 	int ret;
 
-	port->port.flags |= UPF_FIXED_TYPE | UPF_SKIP_TEST;
-	port->port.type = PORT_MCHP16550A;
 	/*
 	 * 8250 core considers prescaller value to be always 16.
 	 * The MCHP ports support downscaled mode and hence the
@@ -687,21 +685,14 @@ static int pci1xxxx_setup(struct pci_dev *pdev,
 	 * The value itself is not really used anywhere except baud
 	 * rate calculations, so we can mangle it as we wish.
 	 */
-	port->port.uartclk = 64 * HZ_PER_MHZ;
-	port->port.set_termios = serial8250_do_set_termios;
-	port->port.get_divisor = pci1xxxx_get_divisor;
-	port->port.set_divisor = pci1xxxx_set_divisor;
-	port->port.rs485_config = pci1xxxx_rs485_config;
-	port->port.rs485_supported = pci1xxxx_rs485_supported;
-
 	/*
 	 * C0 and later revisions support Burst operation.
 	 * RTS workaround in mctrl is applicable only to B0.
 	 */
 	if (rev >= 0xC0)
-		port->port.handle_irq = pci1xxxx_handle_irq;
+		;
 	else if (rev == 0xB0)
-		port->port.set_mctrl = pci1xxxx_set_mctrl;
+		;
 
 	ret = serial8250_pci_setup_port(pdev, port, 0, PORT_OFFSET * port_idx, 0);
 	if (ret < 0)
@@ -805,8 +796,6 @@ static int pci1xxxx_serial_probe(struct pci_dev *pdev,
 	}
 
 	memset(&uart, 0, sizeof(uart));
-	uart.port.flags = UPF_SHARE_IRQ | UPF_FIXED_PORT;
-	uart.port.dev = dev;
 
 	if (num_vectors == max_vec_reqd)
 		writeb(UART_PCI_CTRL_SET_MULTIPLE_MSI, priv->membase + UART_PCI_CTRL_REG);
@@ -817,9 +806,7 @@ static int pci1xxxx_serial_probe(struct pci_dev *pdev,
 		port_idx = pci1xxxx_logical_to_physical_port_translate(subsys_dev, i);
 
 		if (num_vectors == max_vec_reqd)
-			uart.port.irq = pci_irq_vector(pdev, port_idx);
-		else
-			uart.port.irq = pci_irq_vector(pdev, 0);
+			;
 
 		rc = pci1xxxx_setup(pdev, &uart, port_idx, priv->dev_rev);
 		if (rc) {
diff --git a/drivers/tty/serial/8250/8250_pcilib.c b/drivers/tty/serial/8250/8250_pcilib.c
index d8d0ae0d7238..97f4e0c3ef70 100644
--- a/drivers/tty/serial/8250/8250_pcilib.c
+++ b/drivers/tty/serial/8250/8250_pcilib.c
@@ -31,17 +31,7 @@ int serial8250_pci_setup_port(struct pci_dev *dev, struct uart_8250_port *port,
 		if (!pcim_iomap(dev, bar, 0) && !pcim_iomap_table(dev))
 			return -ENOMEM;
 
-		port->port.iotype = UPIO_MEM;
-		port->port.iobase = 0;
-		port->port.mapbase = pci_resource_start(dev, bar) + offset;
-		port->port.membase = pcim_iomap_table(dev)[bar] + offset;
-		port->port.regshift = regshift;
 	} else if (IS_ENABLED(CONFIG_HAS_IOPORT)) {
-		port->port.iotype = UPIO_PORT;
-		port->port.iobase = pci_resource_start(dev, bar) + offset;
-		port->port.mapbase = 0;
-		port->port.membase = NULL;
-		port->port.regshift = 0;
 	} else {
 		return serial_8250_warn_need_ioport(dev);
 	}
diff --git a/drivers/tty/serial/8250/8250_pericom.c b/drivers/tty/serial/8250/8250_pericom.c
index b8d5b7714a9d..fa3ef5505421 100644
--- a/drivers/tty/serial/8250/8250_pericom.c
+++ b/drivers/tty/serial/8250/8250_pericom.c
@@ -112,17 +112,9 @@ static int pericom8250_probe(struct pci_dev *pdev, const struct pci_device_id *i
 
 	memset(&uart, 0, sizeof(uart));
 
-	uart.port.dev = &pdev->dev;
-	uart.port.irq = pdev->irq;
-	uart.port.private_data = pericom;
-	uart.port.iotype = UPIO_PORT;
-	uart.port.uartclk = 921600 * 16;
-	uart.port.flags = UPF_SKIP_TEST | UPF_BOOT_AUTOCONF | UPF_SHARE_IRQ;
-	uart.port.set_divisor = pericom_do_set_divisor;
 	for (i = 0; i < nr && i < maxnr; i++) {
 		unsigned int offset = (i == 3 && nr == 4) ? 0x38 : i * 0x8;
 
-		uart.port.iobase = pci_resource_start(pdev, bar) + offset;
 
 		dev_dbg(&pdev->dev, "Setup PCI port: port %lx, irq %d, type %d\n",
 			uart.port.iobase, uart.port.irq, uart.port.iotype);
diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
index 10f2a5214342..6afa4feeff88 100644
--- a/drivers/tty/serial/8250/8250_platform.c
+++ b/drivers/tty/serial/8250/8250_platform.c
@@ -32,24 +32,14 @@ static int serial8250_probe_acpi(struct platform_device *pdev)
 
 	switch (resource_type(regs)) {
 	case IORESOURCE_IO:
-		uart.port.iobase = regs->start;
 		break;
 	case IORESOURCE_MEM:
-		uart.port.mapbase = regs->start;
-		uart.port.mapsize = resource_size(regs);
-		uart.port.flags = UPF_IOREMAP;
 		break;
 	default:
 		return -EINVAL;
 	}
 
 	/* default clock frequency */
-	uart.port.uartclk = 1843200;
-	uart.port.type = PORT_16550A;
-	uart.port.dev = &pdev->dev;
-	uart.port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
-
-	ret = uart_read_and_validate_port_properties(&uart.port);
 	/* no interrupt -> fall back to polling */
 	if (ret == -ENXIO)
 		ret = 0;
@@ -71,33 +61,6 @@ static int serial8250_probe_platform(struct platform_device *dev, struct plat_se
 	memset(&uart, 0, sizeof(uart));
 
 	for (i = 0; p && p->flags != 0; p++, i++) {
-		uart.port.iobase	= p->iobase;
-		uart.port.membase	= p->membase;
-		uart.port.irq		= p->irq;
-		uart.port.irqflags	= p->irqflags;
-		uart.port.uartclk	= p->uartclk;
-		uart.port.regshift	= p->regshift;
-		uart.port.iotype	= p->iotype;
-		uart.port.flags		= p->flags;
-		uart.port.mapbase	= p->mapbase;
-		uart.port.mapsize	= p->mapsize;
-		uart.port.hub6		= p->hub6;
-		uart.port.has_sysrq	= p->has_sysrq;
-		uart.port.private_data	= p->private_data;
-		uart.port.type		= p->type;
-		uart.bugs		= p->bugs;
-		uart.port.serial_in	= p->serial_in;
-		uart.port.serial_out	= p->serial_out;
-		uart.dl_read		= p->dl_read;
-		uart.dl_write		= p->dl_write;
-		uart.port.handle_irq	= p->handle_irq;
-		uart.port.handle_break	= p->handle_break;
-		uart.port.set_termios	= p->set_termios;
-		uart.port.set_ldisc	= p->set_ldisc;
-		uart.port.get_mctrl	= p->get_mctrl;
-		uart.port.pm		= p->pm;
-		uart.port.dev		= &dev->dev;
-		uart.port.irqflags	|= irqflag;
 		ret = serial8250_register_8250_port(&uart);
 		if (ret < 0) {
 			dev_err(&dev->dev, "unable to register port at index %d "
diff --git a/drivers/tty/serial/8250/8250_pnp.c b/drivers/tty/serial/8250/8250_pnp.c
index 67fbf147aad1..b45df4ad9ae8 100644
--- a/drivers/tty/serial/8250/8250_pnp.c
+++ b/drivers/tty/serial/8250/8250_pnp.c
@@ -446,21 +446,12 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
 
 	memset(&uart, 0, sizeof(uart));
 	if ((flags & CIR_PORT) && pnp_port_valid(dev, 2)) {
-		uart.port.iobase = pnp_port_start(dev, 2);
 	} else if (pnp_port_valid(dev, 0)) {
-		uart.port.iobase = pnp_port_start(dev, 0);
 	} else if (pnp_mem_valid(dev, 0)) {
-		uart.port.mapbase = pnp_mem_start(dev, 0);
-		uart.port.mapsize = pnp_mem_len(dev, 0);
-		uart.port.flags = UPF_IOREMAP;
 	} else
 		return -ENODEV;
 
-	uart.port.uartclk = 1843200;
-	uart.port.dev = &dev->dev;
-	uart.port.flags |= UPF_SKIP_TEST | UPF_BOOT_AUTOCONF;
 
-	ret = uart_read_port_properties(&uart.port);
 	/* no interrupt -> fall back to polling */
 	if (ret == -ENXIO)
 		ret = 0;
@@ -468,8 +459,6 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
 		return ret;
 
 	if (flags & CIR_PORT) {
-		uart.port.flags |= UPF_FIXED_PORT | UPF_FIXED_TYPE;
-		uart.port.type = PORT_8250_CIR;
 	}
 
 	dev_info(&dev->dev,
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 8f4359cf42eb..f569584172a3 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -3212,11 +3212,11 @@ void serial8250_set_defaults(struct uart_8250_port *up)
 		unsigned int type = up->port.type;
 
 		if (!up->port.fifosize)
-			up->port.fifosize = uart_config[type].fifo_size;
+			;
 		if (!up->tx_loadsz)
-			up->tx_loadsz = uart_config[type].tx_loadsz;
+			;
 		if (!up->capabilities)
-			up->capabilities = uart_config[type].flags;
+			;
 	}
 
 	set_io_from_upio(port);
@@ -3224,9 +3224,9 @@ void serial8250_set_defaults(struct uart_8250_port *up)
 	/* default dma handlers */
 	if (up->dma) {
 		if (!up->dma->tx_dma)
-			up->dma->tx_dma = serial8250_tx_dma;
+			;
 		if (!up->dma->rx_dma)
-			up->dma->rx_dma = serial8250_rx_dma;
+			;
 	}
 }
 EXPORT_SYMBOL_GPL(serial8250_set_defaults);
diff --git a/drivers/tty/serial/8250/8250_pxa.c b/drivers/tty/serial/8250/8250_pxa.c
index 656974dce062..09d93954307e 100644
--- a/drivers/tty/serial/8250/8250_pxa.c
+++ b/drivers/tty/serial/8250/8250_pxa.c
@@ -110,23 +110,9 @@ static int serial_pxa_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	uart.port.type = PORT_XSCALE;
-	uart.port.mapbase = mmres->start;
-	uart.port.flags = UPF_IOREMAP | UPF_SKIP_TEST | UPF_FIXED_TYPE;
-	uart.port.dev = &pdev->dev;
-	uart.port.uartclk = clk_get_rate(data->clk);
-	uart.port.pm = serial_pxa_pm;
-	uart.port.private_data = data;
-
-	ret = uart_read_port_properties(&uart.port);
 	if (ret)
 		return ret;
 
-	uart.port.iotype = UPIO_MEM32;
-	uart.port.regshift = 2;
-	uart.port.fifosize = 64;
-	uart.tx_loadsz = 32;
-	uart.dl_write = serial_pxa_dl_write;
 
 	ret = serial8250_register_8250_port(&uart);
 	if (ret < 0)
diff --git a/drivers/tty/serial/8250/8250_rt288x.c b/drivers/tty/serial/8250/8250_rt288x.c
index bf28b8a9a710..9ab928c7bfcc 100644
--- a/drivers/tty/serial/8250/8250_rt288x.c
+++ b/drivers/tty/serial/8250/8250_rt288x.c
@@ -83,17 +83,6 @@ int rt288x_setup(struct uart_port *p)
 {
 	struct uart_8250_port *up = up_to_u8250p(p);
 
-	p->iotype = UPIO_AU;
-
-	p->serial_in = au_serial_in;
-	p->serial_out = au_serial_out;
-	up->dl_read = au_serial_dl_read;
-	up->dl_write = au_serial_dl_write;
-
-	p->mapsize = 0x100;
-
-	up->bugs |= UART_BUG_NOMSR;
-
 	return 0;
 }
 EXPORT_SYMBOL_GPL(rt288x_setup);
diff --git a/drivers/tty/serial/8250/8250_tegra.c b/drivers/tty/serial/8250/8250_tegra.c
index 2f3b0075763f..c55a76c2d370 100644
--- a/drivers/tty/serial/8250/8250_tegra.c
+++ b/drivers/tty/serial/8250/8250_tegra.c
@@ -57,29 +57,18 @@ static int tegra_uart_probe(struct platform_device *pdev)
 	port = &port8250.port;
 	spin_lock_init(&port->lock);
 
-	port->flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	port->type = PORT_TEGRA;
-	port->dev = &pdev->dev;
-	port->handle_break = tegra_uart_handle_break;
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res)
 		return -ENODEV;
 
-	port->membase = devm_ioremap(&pdev->dev, res->start,
-				     resource_size(res));
 	if (!port->membase)
 		return -ENOMEM;
 
-	port->mapbase = res->start;
-	port->mapsize = resource_size(res);
 
-	ret = uart_read_port_properties(port);
 	if (ret)
 		return ret;
 
-	port->iotype = UPIO_MEM32;
-	port->regshift = 2;
 
 	uart->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
 	if (IS_ERR(uart->rst))
@@ -96,7 +85,6 @@ static int tegra_uart_probe(struct platform_device *pdev)
 		if (ret < 0)
 			return ret;
 
-		port->uartclk = clk_get_rate(uart->clk);
 	}
 
 	ret = reset_control_deassert(uart->rst);
diff --git a/drivers/tty/serial/8250/8250_uniphier.c b/drivers/tty/serial/8250/8250_uniphier.c
index e3db60bf50c9..cf90f5c31e28 100644
--- a/drivers/tty/serial/8250/8250_uniphier.c
+++ b/drivers/tty/serial/8250/8250_uniphier.c
@@ -190,34 +190,15 @@ static int uniphier_uart_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	up.port.uartclk = clk_get_rate(priv->clk);
 
-	spin_lock_init(&priv->atomic_write_lock);
 
-	up.port.dev = dev;
-	up.port.private_data = priv;
-	up.port.mapbase = regs->start;
-	up.port.mapsize = resource_size(regs);
-	up.port.membase = membase;
 
-	ret = uart_read_port_properties(&up.port);
 	if (ret)
 		return ret;
 
-	up.port.type = PORT_16550A;
-	up.port.iotype = UPIO_MEM32;
-	up.port.fifosize = 64;
-	up.port.regshift = UNIPHIER_UART_REGSHIFT;
-	up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE;
-	up.capabilities = UART_CAP_FIFO;
 
 	if (of_property_read_bool(dev->of_node, "auto-flow-control"))
-		up.capabilities |= UART_CAP_AFE;
-
-	up.port.serial_in = uniphier_serial_in;
-	up.port.serial_out = uniphier_serial_out;
-	up.dl_read = uniphier_serial_dl_read;
-	up.dl_write = uniphier_serial_dl_write;
+		;
 
 	ret = serial8250_register_8250_port(&up);
 	if (ret < 0) {
diff --git a/drivers/tty/serial/8250/serial_cs.c b/drivers/tty/serial/8250/serial_cs.c
index 58e279ea7ee0..74b75f2e3195 100644
--- a/drivers/tty/serial/8250/serial_cs.c
+++ b/drivers/tty/serial/8250/serial_cs.c
@@ -101,7 +101,6 @@ struct serial_info {
  */
 static void quirk_setup_brainboxes_0104(struct pcmcia_device *link, struct uart_8250_port *uart)
 {
-	uart->port.uartclk = 14745600;
 }
 
 static int quirk_post_ibm(struct pcmcia_device *link)
@@ -350,13 +349,8 @@ static int setup_serial(struct pcmcia_device *handle, struct serial_info *info,
 	int line;
 
 	memset(&uart, 0, sizeof(uart));
-	uart.port.iobase = iobase;
-	uart.port.irq = irq;
-	uart.port.flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_SHARE_IRQ;
-	uart.port.uartclk = 1843200;
-	uart.port.dev = &handle->dev;
 	if (buggy_uart)
-		uart.port.flags |= UPF_BUGGY_UART;
+		;
 
 	if (info->quirk && info->quirk->setup)
 		info->quirk->setup(handle, &uart);
diff --git a/drivers/tty/serial/serial_port.c b/drivers/tty/serial/serial_port.c
index 2fc48cd63f6c..4d471d50f0f8 100644
--- a/drivers/tty/serial/serial_port.c
+++ b/drivers/tty/serial/serial_port.c
@@ -203,32 +203,24 @@ static int __uart_read_properties(struct uart_port *port, bool use_defaults)
 	int ret;
 
 	/* Read optional UART functional clock frequency */
-	device_property_read_u32(dev, "clock-frequency", &port->uartclk);
 
 	/* Read the registers alignment (default: 8-bit) */
 	ret = device_property_read_u32(dev, "reg-shift", &value);
 	if (ret)
-		port->regshift = use_defaults ? 0 : port->regshift;
 	else
-		port->regshift = value;
 
 	/* Read the registers I/O access type (default: MMIO 8-bit) */
 	ret = device_property_read_u32(dev, "reg-io-width", &value);
 	if (ret) {
-		port->iotype = port->iobase ? UPIO_PORT : UPIO_MEM;
 	} else {
 		switch (value) {
 		case 1:
-			port->iotype = UPIO_MEM;
 			break;
 		case 2:
-			port->iotype = UPIO_MEM16;
 			break;
 		case 4:
-			port->iotype = device_is_big_endian(dev) ? UPIO_MEM32BE : UPIO_MEM32;
 			break;
 		default:
-			port->iotype = UPIO_UNKNOWN;
 			break;
 		}
 	}
@@ -249,19 +241,13 @@ static int __uart_read_properties(struct uart_port *port, bool use_defaults)
 		return -EINVAL;
 	}
 
-	port->mapbase += value;
-	port->mapsize -= value;
-
 	/* Read optional FIFO size */
-	device_property_read_u32(dev, "fifo-size", &port->fifosize);
 
 	if (device_property_read_bool(dev, "no-loopback-test"))
-		port->flags |= UPF_SKIP_TEST;
 
 	/* Get index of serial line, if found in DT aliases */
 	ret = of_alias_get_id(dev_of_node(dev), "serial");
 	if (ret >= 0)
-		port->line = ret;
 
 	if (dev_is_platform(dev))
 		ret = platform_get_irq(to_platform_device(dev), 0);
@@ -274,14 +260,11 @@ static int __uart_read_properties(struct uart_port *port, bool use_defaults)
 	if (ret == -EPROBE_DEFER)
 		return ret;
 	if (ret > 0)
-		port->irq = ret;
 	else if (use_defaults)
 		/* By default IRQ support is mandatory */
 		return ret;
 	else
-		port->irq = 0;
 
-	port->flags |= UPF_SHARE_IRQ;
 
 	return 0;
 }

Re: [PATCH v3 0/2] serial: 8250_platform: Reduce stack usage in probe functions

[Andy Shevchenko]

On Thu, Aug 07, 2025 at 03:21:32AM +0530, Abinash Singh wrote:
> On Wed, 6 Aug 2025 23:39 Andy Shevchenko wrote:
> > Have you had a chance to see Arnd's comments?
> >
> Yeah ,I have made comments on that.
> Please check that and provide feedback.
> 
> Hi,
> Apologies for not reviewing the patch carefully before submitting it.
> It's 3 A.M. here, and I’m still up, so I missed it

If others are okay with this intermediate step,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko