[PATCH v2 0/2] serial: qcom-geni: Add support to increase UART ports efficiently

[PATCH v2 0/2] serial: qcom-geni: Add support to increase UART ports efficiently

[Zong Jiang]

This patch series improves the flexibility and scalability of the
Qualcomm GENI serial driver by refactoring UART port allocation and
introducing a Kconfig option to configure the number of supported
UART ports.

Changes since v1:
- Based on Greg KH's comments, the following changes have been made in v2:
  - Split the original patch into two separate patches.
  - Replaced static UART port allocation with dynamic allocation.
  - Added a Kconfig option to configure UART port count.
  - Improved commit messages and changelog to better justify the changes.

Patch 1 replaces the hardcoded static array of UART ports with dynamic
allocation, reducing memory usage and improving maintainability.

Patch 2 introduces a new Kconfig option,
SERIAL_QCOM_GENI_UART_PORTS, allowing platforms to configure the
maximum number of UART ports at build time.

These changes are useful for platforms that require more than the
previously hardcoded number of UART ports, and help avoid unnecessary
allocation for unused ports.

Patch summary:
  [PATCH v2 1/2] serial: qcom-geni: Dynamically allocate UART ports
  [PATCH v2 2/2] serial: qcom-geni: Make UART port count configurable via Kconfig

Signed-off-by: Zong Jiang <quic_zongjian@quicinc.com> 

[PATCH 1/2] serial: qcom-geni: Dynamically allocate UART ports

[Zong Jiang]

Replace the static allocation of UART ports with dynamic allocation
using devm_kzalloc. This change removes the fixed-size array and instead
allocates each UART port structure on demand during probe, improving
memory efficiency and scalability.

Signed-off-by: Zong Jiang <quic_zongjian@quicinc.com>
---
 drivers/tty/serial/qcom_geni_serial.c | 44 ++++++++-------------------
 1 file changed, 12 insertions(+), 32 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 32ec632fd080..080c18ddbdde 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -164,33 +164,6 @@ static inline struct qcom_geni_serial_port *to_dev_port(struct uart_port *uport)
 	return container_of(uport, struct qcom_geni_serial_port, uport);
 }
 
-static struct qcom_geni_serial_port qcom_geni_uart_ports[GENI_UART_PORTS] = {
-	[0] = {
-		.uport = {
-			.iotype = UPIO_MEM,
-			.ops = &qcom_geni_uart_pops,
-			.flags = UPF_BOOT_AUTOCONF,
-			.line = 0,
-		},
-	},
-	[1] = {
-		.uport = {
-			.iotype = UPIO_MEM,
-			.ops = &qcom_geni_uart_pops,
-			.flags = UPF_BOOT_AUTOCONF,
-			.line = 1,
-		},
-	},
-	[2] = {
-		.uport = {
-			.iotype = UPIO_MEM,
-			.ops = &qcom_geni_uart_pops,
-			.flags = UPF_BOOT_AUTOCONF,
-			.line = 2,
-		},
-	},
-};
-
 static struct qcom_geni_serial_port qcom_geni_console_port = {
 	.uport = {
 		.iotype = UPIO_MEM,
@@ -285,7 +258,7 @@ static const char *qcom_geni_serial_get_type(struct uart_port *uport)
 	return "MSM";
 }
 
-static struct qcom_geni_serial_port *get_port_from_line(int line, bool console)
+static struct qcom_geni_serial_port *get_port_from_line(int line, bool console, struct device *dev)
 {
 	struct qcom_geni_serial_port *port;
 	int nr_ports = console ? GENI_UART_CONS_PORTS : GENI_UART_PORTS;
@@ -306,7 +279,14 @@ static struct qcom_geni_serial_port *get_port_from_line(int line, bool console)
 		if (line < 0)
 			return ERR_PTR(-ENXIO);
 
-		port = &qcom_geni_uart_ports[line];
+		port = devm_kzalloc(dev, sizeof(*port), GFP_KERNEL);
+		if (!port)
+			return ERR_PTR(-ENOMEM);
+
+		port->uport.iotype = UPIO_MEM;
+		port->uport.ops = &qcom_geni_uart_pops;
+		port->uport.flags = UPF_BOOT_AUTOCONF;
+		port->uport.line = line;
 	}
 	return port;
 }
@@ -554,7 +534,7 @@ static void qcom_geni_serial_console_write(struct console *co, const char *s,
 
 	WARN_ON(co->index < 0 || co->index >= GENI_UART_CONS_PORTS);
 
-	port = get_port_from_line(co->index, true);
+	port = get_port_from_line(co->index, true, NULL);
 	if (IS_ERR(port))
 		return;
 
@@ -1511,7 +1491,7 @@ static int qcom_geni_console_setup(struct console *co, char *options)
 	if (co->index >= GENI_UART_CONS_PORTS  || co->index < 0)
 		return -ENXIO;
 
-	port = get_port_from_line(co->index, true);
+	port = get_port_from_line(co->index, true, NULL);
 	if (IS_ERR(port)) {
 		pr_err("Invalid line %d\n", co->index);
 		return PTR_ERR(port);
@@ -1866,7 +1846,7 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
 			line = of_alias_get_id(pdev->dev.of_node, "hsuart");
 	}
 
-	port = get_port_from_line(line, data->console);
+	port = get_port_from_line(line, data->console, &pdev->dev);
 	if (IS_ERR(port)) {
 		dev_err(&pdev->dev, "Invalid line %d\n", line);
 		return PTR_ERR(port);
-- 
2.34.1

[PATCH 2/2] serial: qcom-geni: Make UART port count configurable via Kconfig

[Zong Jiang]

Replace the hardcoded GENI_UART_PORTS macro with a new Kconfig option
SERIAL_QCOM_GENI_UART_PORTS to allow platforms to configure the maximum
number of UART ports supported by the driver at build time.

This improves flexibility for platforms that require more than the
previously fixed number of UART ports, and avoids unnecessary allocation
for unused ports.

Signed-off-by: Zong Jiang <quic_zongjian@quicinc.com>
---
 drivers/tty/serial/Kconfig            | 8 ++++++++
 drivers/tty/serial/qcom_geni_serial.c | 5 ++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 44427415a80d..e661f5951f55 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -928,6 +928,14 @@ config SERIAL_QCOM_GENI_CONSOLE
 	  Serial console driver for Qualcomm Technologies Inc's GENI based
 	  QUP hardware.
 
+config SERIAL_QCOM_GENI_UART_PORTS
+	int "Maximum number of GENI UART ports"
+	depends on SERIAL_QCOM_GENI
+	default "8"
+	help
+	  Set this to the maximum number of serial ports you want the driver
+	  to support.
+
 config SERIAL_VT8500
 	bool "VIA VT8500 on-chip serial port support"
 	depends on ARCH_VT8500 || COMPILE_TEST
diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 080c18ddbdde..9c7b1cea7cfe 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -77,7 +77,6 @@
 #define STALE_TIMEOUT			16
 #define DEFAULT_BITS_PER_CHAR		10
 #define GENI_UART_CONS_PORTS		1
-#define GENI_UART_PORTS			3
 #define DEF_FIFO_DEPTH_WORDS		16
 #define DEF_TX_WM			2
 #define DEF_FIFO_WIDTH_BITS		32
@@ -261,7 +260,7 @@ static const char *qcom_geni_serial_get_type(struct uart_port *uport)
 static struct qcom_geni_serial_port *get_port_from_line(int line, bool console, struct device *dev)
 {
 	struct qcom_geni_serial_port *port;
-	int nr_ports = console ? GENI_UART_CONS_PORTS : GENI_UART_PORTS;
+	int nr_ports = console ? GENI_UART_CONS_PORTS : CONFIG_SERIAL_QCOM_GENI_UART_PORTS;
 
 	if (console) {
 		if (line < 0 || line >= nr_ports)
@@ -1652,7 +1651,7 @@ static struct uart_driver qcom_geni_uart_driver = {
 	.owner = THIS_MODULE,
 	.driver_name = "qcom_geni_uart",
 	.dev_name = "ttyHS",
-	.nr =  GENI_UART_PORTS,
+	.nr = CONFIG_SERIAL_QCOM_GENI_UART_PORTS,
 };
 
 static int geni_serial_resources_on(struct uart_port *uport)
-- 
2.34.1

Re: [PATCH 2/2] serial: qcom-geni: Make UART port count configurable via Kconfig

[Greg KH]

On Tue, Aug 12, 2025 at 01:48:19PM +0800, Zong Jiang wrote:
> Replace the hardcoded GENI_UART_PORTS macro with a new Kconfig option
> SERIAL_QCOM_GENI_UART_PORTS to allow platforms to configure the maximum
> number of UART ports supported by the driver at build time.
> 
> This improves flexibility for platforms that require more than the
> previously fixed number of UART ports, and avoids unnecessary allocation
> for unused ports.
> 
> Signed-off-by: Zong Jiang <quic_zongjian@quicinc.com>
> ---
>  drivers/tty/serial/Kconfig            | 8 ++++++++
>  drivers/tty/serial/qcom_geni_serial.c | 5 ++---
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 44427415a80d..e661f5951f55 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -928,6 +928,14 @@ config SERIAL_QCOM_GENI_CONSOLE
>  	  Serial console driver for Qualcomm Technologies Inc's GENI based
>  	  QUP hardware.
>  
> +config SERIAL_QCOM_GENI_UART_PORTS
> +	int "Maximum number of GENI UART ports"
> +	depends on SERIAL_QCOM_GENI
> +	default "8"
> +	help
> +	  Set this to the maximum number of serial ports you want the driver
> +	  to support.

Why do you need a static number of ports at all?  Why not just handle
how ever many there are in the system at the moment?  Or is this due to
some restriction in the serial core that requires this?

thanks,

greg k-h

RE: [PATCH 2/2] serial: qcom-geni: Make UART port count configurable via Kconfig

[Zong Jiang (QUIC)]

Hi Greg,

Thanks for the question!

Yes, this is indeed due to a restriction in the serial core. Specifically, the serial core requires the uart_driver->nr field to be set at registration time via uart_register_driver(). This value determines how many uart_port slots are allocated internally, it cannot be changed dynamically afterward. As a result, we need to define the maximum number of ports up front.

By making this configurable via Kconfig, platforms can tailor the driver to match their actual hardware needs, avoiding unnecessary allocation for unused ports while still complying with the serial core's expectations.

Thanks again for the feedback!

Best regards,
Zong Jiang


-----Original Message-----
From: Greg KH <gregkh@linuxfoundation.org> 
Sent: Tuesday, August 12, 2025 2:30 PM
To: Zong Jiang (QUIC) <quic_zongjian@quicinc.com>
Cc: linux-serial@vger.kernel.org; linux-kernel@vger.kernel.org; Zhiqiang Tu (QUIC) <quic_ztu@quicinc.com>; Anup Kulkarni (QUIC) <quic_anupkulk@quicinc.com>; Mukesh Savaliya (QUIC) <quic_msavaliy@quicinc.com>; Viken Dadhaniya (QUIC) <quic_vdadhani@quicinc.com>
Subject: Re: [PATCH 2/2] serial: qcom-geni: Make UART port count configurable via Kconfig

On Tue, Aug 12, 2025 at 01:48:19PM +0800, Zong Jiang wrote:
> Replace the hardcoded GENI_UART_PORTS macro with a new Kconfig option 
> SERIAL_QCOM_GENI_UART_PORTS to allow platforms to configure the 
> maximum number of UART ports supported by the driver at build time.
> 
> This improves flexibility for platforms that require more than the 
> previously fixed number of UART ports, and avoids unnecessary 
> allocation for unused ports.
> 
> Signed-off-by: Zong Jiang <quic_zongjian@quicinc.com>
> ---
>  drivers/tty/serial/Kconfig            | 8 ++++++++
>  drivers/tty/serial/qcom_geni_serial.c | 5 ++---
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig 
> index 44427415a80d..e661f5951f55 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -928,6 +928,14 @@ config SERIAL_QCOM_GENI_CONSOLE
>  	  Serial console driver for Qualcomm Technologies Inc's GENI based
>  	  QUP hardware.
>  
> +config SERIAL_QCOM_GENI_UART_PORTS
> +	int "Maximum number of GENI UART ports"
> +	depends on SERIAL_QCOM_GENI
> +	default "8"
> +	help
> +	  Set this to the maximum number of serial ports you want the driver
> +	  to support.

Why do you need a static number of ports at all?  Why not just handle how ever many there are in the system at the moment?  Or is this due to some restriction in the serial core that requires this?

thanks,

greg k-h