[PATCH 0/4] serial: sc16is7xx: backport FIFO fixes for linux-5.15.y

[PATCH 0/4] serial: sc16is7xx: backport FIFO fixes for linux-5.15.y

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Hello,
this patch series brings additional patches to fix some FIFO issues when
backporting to linux-5.15.y for the sc16is7xx driver.

Commit ("serial: sc16is7xx: add missing support for rs485 devicetree
properties") is required when using RS-485.

Commit ("serial: sc16is7xx: refactor FIFO access functions
to increase commonality") is a prerequisite for commit ("serial:
sc16is7xx: fix TX fifo corruption"). Altough it is not strictly
necessary, it makes backporting easier.

I have tested the changes on a custom board with two SC16IS752 DUART over
a SPI interface using a Variscite IMX8MN NANO SOM. The four UARTs are
configured in RS-485 mode.

Thank you.

Hugo Villeneuve (4):
  serial: sc16is7xx: add missing support for rs485 devicetree properties
  serial: sc16is7xx: refactor FIFO access functions to increase
    commonality
  serial: sc16is7xx: fix TX fifo corruption
  serial: sc16is7xx: fix invalid FIFO access with special register set

 drivers/tty/serial/sc16is7xx.c | 38 ++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 16 deletions(-)


-- 
2.39.5

[PATCH 1/4] serial: sc16is7xx: add missing support for rs485 devicetree properties

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Retrieve rs485 devicetree properties on registration of sc16is7xx ports in
case they are attached to an rs485 transceiver.

Reworked to fix conflicts when backporting to linux-5.15.y.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Lech Perczak <lech.perczak@camlingroup.com>
Tested-by: Lech Perczak <lech.perczak@camlingroup.com>
Link: https://lore.kernel.org/r/20230807214556.540627-7-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/sc16is7xx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 692c14d7f7d1a..3d3f66563b73b 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1307,6 +1307,10 @@ static int sc16is7xx_probe(struct device *dev,
 
 		mutex_init(&s->p[i].efr_lock);
 
+		ret = uart_get_rs485_mode(&s->p[i].port);
+		if (ret)
+			goto out_ports;
+
 		/* Disable all interrupts */
 		sc16is7xx_port_write(&s->p[i].port, SC16IS7XX_IER_REG, 0);
 		/* Disable TX/RX */
-- 
2.39.5

[PATCH 2/4] serial: sc16is7xx: refactor FIFO access functions to increase commonality

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Simplify FIFO access functions by avoiding to declare
a struct sc16is7xx_port *s variable within each function.

This is mainly done to have more commonality between the max310x and
sc16is7xx drivers.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20231221231823.2327894-15-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/sc16is7xx.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 3d3f66563b73b..591f97e78cdb7 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -361,17 +361,15 @@ static void sc16is7xx_port_write(struct uart_port *port, u8 reg, u8 val)
 	regmap_write(one->regmap, reg, val);
 }
 
-static void sc16is7xx_fifo_read(struct uart_port *port, unsigned int rxlen)
+static void sc16is7xx_fifo_read(struct uart_port *port, u8 *rxbuf, unsigned int rxlen)
 {
-	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 
-	regmap_noinc_read(one->regmap, SC16IS7XX_RHR_REG, s->buf, rxlen);
+	regmap_noinc_read(one->regmap, SC16IS7XX_RHR_REG, rxbuf, rxlen);
 }
 
-static void sc16is7xx_fifo_write(struct uart_port *port, u8 to_send)
+static void sc16is7xx_fifo_write(struct uart_port *port, u8 *txbuf, u8 to_send)
 {
-	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 
 	/*
@@ -381,7 +379,7 @@ static void sc16is7xx_fifo_write(struct uart_port *port, u8 to_send)
 	if (unlikely(!to_send))
 		return;
 
-	regmap_noinc_write(one->regmap, SC16IS7XX_THR_REG, s->buf, to_send);
+	regmap_noinc_write(one->regmap, SC16IS7XX_THR_REG, txbuf, to_send);
 }
 
 static void sc16is7xx_port_update(struct uart_port *port, u8 reg,
@@ -583,7 +581,7 @@ static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
 			s->buf[0] = sc16is7xx_port_read(port, SC16IS7XX_RHR_REG);
 			bytes_read = 1;
 		} else {
-			sc16is7xx_fifo_read(port, rxlen);
+			sc16is7xx_fifo_read(port, s->buf, rxlen);
 			bytes_read = rxlen;
 		}
 
@@ -670,7 +668,7 @@ static void sc16is7xx_handle_tx(struct uart_port *port)
 			xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
 		}
 
-		sc16is7xx_fifo_write(port, to_send);
+		sc16is7xx_fifo_write(port, s->buf, to_send);
 	}
 
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-- 
2.39.5

[PATCH 3/4] serial: sc16is7xx: fix TX fifo corruption

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Sometimes, when a packet is received on channel A at almost the same time
as a packet is about to be transmitted on channel B, we observe with a
logic analyzer that the received packet on channel A is transmitted on
channel B. In other words, the Tx buffer data on channel B is corrupted
with data from channel A.

The problem appeared since commit 4409df5866b7 ("serial: sc16is7xx: change
EFR lock to operate on each channels"), which changed the EFR locking to
operate on each channel instead of chip-wise.

This commit has introduced a regression, because the EFR lock is used not
only to protect the EFR registers access, but also, in a very obscure and
undocumented way, to protect access to the data buffer, which is shared by
the Tx and Rx handlers, but also by each channel of the IC.

Fix this regression first by switching to kfifo_out_linear_ptr() in
sc16is7xx_handle_tx() to eliminate the need for a shared Rx/Tx buffer.

Secondly, replace the chip-wise Rx buffer with a separate Rx buffer for
each channel.

Reworked to fix conflicts when backporting to linux-5.15.y.

Fixes: 4409df5866b7 ("serial: sc16is7xx: change EFR lock to operate on each channels")
Cc: stable@vger.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240723125302.1305372-2-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/sc16is7xx.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 591f97e78cdb7..928c701f0c35a 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -318,6 +318,7 @@ struct sc16is7xx_one {
 	struct kthread_work		tx_work;
 	struct kthread_work		reg_work;
 	struct sc16is7xx_one_config	config;
+	unsigned char			buf[SC16IS7XX_FIFO_SIZE]; /* Rx buffer. */
 	bool				irda_mode;
 };
 
@@ -327,7 +328,6 @@ struct sc16is7xx_port {
 #ifdef CONFIG_GPIOLIB
 	struct gpio_chip		gpio;
 #endif
-	unsigned char			buf[SC16IS7XX_FIFO_SIZE];
 	struct kthread_worker		kworker;
 	struct task_struct		*kworker_task;
 	struct sc16is7xx_one		p[];
@@ -555,17 +555,17 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
 				unsigned int iir)
 {
-	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
+	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 	unsigned int lsr = 0, ch, flag, bytes_read, i;
 	bool read_lsr = (iir == SC16IS7XX_IIR_RLSE_SRC) ? true : false;
 
-	if (unlikely(rxlen >= sizeof(s->buf))) {
+	if (unlikely(rxlen >= sizeof(one->buf))) {
 		dev_warn_ratelimited(port->dev,
 				     "ttySC%i: Possible RX FIFO overrun: %d\n",
 				     port->line, rxlen);
 		port->icount.buf_overrun++;
 		/* Ensure sanity of RX level */
-		rxlen = sizeof(s->buf);
+		rxlen = sizeof(one->buf);
 	}
 
 	while (rxlen) {
@@ -578,10 +578,10 @@ static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
 			lsr = 0;
 
 		if (read_lsr) {
-			s->buf[0] = sc16is7xx_port_read(port, SC16IS7XX_RHR_REG);
+			one->buf[0] = sc16is7xx_port_read(port, SC16IS7XX_RHR_REG);
 			bytes_read = 1;
 		} else {
-			sc16is7xx_fifo_read(port, s->buf, rxlen);
+			sc16is7xx_fifo_read(port, one->buf, rxlen);
 			bytes_read = rxlen;
 		}
 
@@ -614,7 +614,7 @@ static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
 		}
 
 		for (i = 0; i < bytes_read; ++i) {
-			ch = s->buf[i];
+			ch = one->buf[i];
 			if (uart_handle_sysrq_char(port, ch))
 				continue;
 
@@ -632,7 +632,7 @@ static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,
 
 static void sc16is7xx_handle_tx(struct uart_port *port)
 {
-	struct sc16is7xx_port *s = dev_get_drvdata(port->dev);
+	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 	struct circ_buf *xmit = &port->state->xmit;
 	unsigned int txlen, to_send, i;
 
@@ -664,11 +664,11 @@ static void sc16is7xx_handle_tx(struct uart_port *port)
 
 		/* Convert to linear buffer */
 		for (i = 0; i < to_send; ++i) {
-			s->buf[i] = xmit->buf[xmit->tail];
+			one->buf[i] = xmit->buf[xmit->tail];
 			xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
 		}
 
-		sc16is7xx_fifo_write(port, s->buf, to_send);
+		sc16is7xx_fifo_write(port, one->buf, to_send);
 	}
 
 	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
-- 
2.39.5

[PATCH 4/4] serial: sc16is7xx: fix invalid FIFO access with special register set

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

When enabling access to the special register set, Receiver time-out and
RHR interrupts can happen. In this case, the IRQ handler will try to read
from the FIFO thru the RHR register at address 0x00, but address 0x00 is
mapped to DLL register, resulting in erroneous FIFO reading.

Call graph example:
    sc16is7xx_startup(): entry
    sc16is7xx_ms_proc(): entry
    sc16is7xx_set_termios(): entry
    sc16is7xx_set_baud(): DLH/DLL = $009C --> access special register set
    sc16is7xx_port_irq() entry            --> IIR is 0x0C
    sc16is7xx_handle_rx() entry
    sc16is7xx_fifo_read(): --> unable to access FIFO (RHR) because it is
                               mapped to DLL (LCR=LCR_CONF_MODE_A)
    sc16is7xx_set_baud(): exit --> Restore access to general register set

Fix the problem by claiming the efr_lock mutex when accessing the Special
register set.

Reworked to fix conflicts when backporting to linux-5.15.y.

Fixes: dfeae619d781 ("serial: sc16is7xx")
Cc: stable@vger.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240723125302.1305372-3-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/sc16is7xx.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 928c701f0c35a..3b7c238793ef4 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -537,6 +537,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 			      prescaler == 1 ? 0 : SC16IS7XX_MCR_CLKSEL_BIT);
 
 	/* Open the LCR divisors for configuration */
+	mutex_lock(&one->efr_lock);
+
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG,
 			     SC16IS7XX_LCR_CONF_MODE_A);
 
@@ -549,6 +551,8 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 	/* Put LCR back to the normal mode */
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
 
+	mutex_unlock(&one->efr_lock);
+
 	return DIV_ROUND_CLOSEST((clk / prescaler) / 16, div);
 }
 
-- 
2.39.5

Re: [PATCH 2/4] serial: sc16is7xx: refactor FIFO access functions to increase commonality

[kernel test robot]

Hi,

Thanks for your patch.

FYI: kernel test robot notices the stable kernel rule is not satisfied.

The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html#option-1

Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree.
Subject: [PATCH 2/4] serial: sc16is7xx: refactor FIFO access functions to increase commonality
Link: https://lore.kernel.org/stable/20241216191818.1553557-3-hugo%40hugovil.com

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 1/4] serial: sc16is7xx: add missing support for rs485 devicetree properties

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

Found matching upstream commit: b4a778303ea0fcabcaff974721477a5743e1f8ec

WARNING: Author mismatch between patch and found commit:
Backport author: Hugo Villeneuve <hugo@hugovil.com>
Commit author: Hugo Villeneuve <hvilleneuve@dimonoff.com>


Status in newer kernel trees:
6.12.y | Present (exact SHA1)

Note: The patch differs from the upstream commit:
---
Failed to apply patch cleanly, falling back to interdiff...

interdiff error output:
/home/sasha/stable/mailbot.sh: line 525: interdiff: command not found
interdiff failed, falling back to standard diff...
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Failed     |  N/A       |
| stable/linux-6.6.y        |  Failed     |  N/A       |
| stable/linux-6.1.y        |  Failed     |  N/A       |
| stable/linux-5.15.y       |  Failed     |  N/A       |
| stable/linux-5.10.y       |  Failed     |  N/A       |
| stable/linux-5.4.y        |  Failed     |  N/A       |

Re: [PATCH 1/4] serial: sc16is7xx: add missing support for rs485 devicetree properties

[Greg Kroah-Hartman]

On Mon, Dec 16, 2024 at 02:18:15PM -0500, Hugo Villeneuve wrote:
> From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> 
> Retrieve rs485 devicetree properties on registration of sc16is7xx ports in
> case they are attached to an rs485 transceiver.
> 
> Reworked to fix conflicts when backporting to linux-5.15.y.
> 
> Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> Reviewed-by: Lech Perczak <lech.perczak@camlingroup.com>
> Tested-by: Lech Perczak <lech.perczak@camlingroup.com>
> Link: https://lore.kernel.org/r/20230807214556.540627-7-hugo@hugovil.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

I do not see any commit ids on this series matching up with what is in
Linus's tree.  Please fix up and resend the series.

thanks,

greg k-h

Re: [PATCH 1/4] serial: sc16is7xx: add missing support for rs485 devicetree properties

[Hugo Villeneuve]

On Tue, 17 Dec 2024 07:41:32 +0100
Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:

> On Mon, Dec 16, 2024 at 02:18:15PM -0500, Hugo Villeneuve wrote:
> > From: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> > 
> > Retrieve rs485 devicetree properties on registration of sc16is7xx ports in
> > case they are attached to an rs485 transceiver.
> > 
> > Reworked to fix conflicts when backporting to linux-5.15.y.
> > 
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
> > Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
> > Reviewed-by: Lech Perczak <lech.perczak@camlingroup.com>
> > Tested-by: Lech Perczak <lech.perczak@camlingroup.com>
> > Link: https://lore.kernel.org/r/20230807214556.540627-7-hugo@hugovil.com
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> I do not see any commit ids on this series matching up with what is in
> Linus's tree.  Please fix up and resend the series.

Ok will do. I will first submit only this patch to make sure my
submission follows the stable guidelines.

Hugo.

-- 
Hugo Villeneuve