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* [PATCH 0/2] serial: stm32: fix software flow control
@ 2022-01-11 16:44 ` Valentin Caron
  0 siblings, 0 replies; 6+ messages in thread
From: Valentin Caron @ 2022-01-11 16:44 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, Erwan Le Ray,
	Valentin Caron, linux-serial, linux-stm32, linux-arm-kernel,
	linux-kernel

This serie fix issues on STM32 USART driver when using software flow control.

Valentin Caron (2):
  serial: stm32: prevent TDR register overwrite when sending x_char
  serial: stm32: fix software flow control transfer

 drivers/tty/serial/stm32-usart.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

-- 
2.17.1


^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH 0/2] serial: stm32: fix software flow control
@ 2022-01-11 16:44 ` Valentin Caron
  0 siblings, 0 replies; 6+ messages in thread
From: Valentin Caron @ 2022-01-11 16:44 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, Erwan Le Ray,
	Valentin Caron, linux-serial, linux-stm32, linux-arm-kernel,
	linux-kernel

This serie fix issues on STM32 USART driver when using software flow control.

Valentin Caron (2):
  serial: stm32: prevent TDR register overwrite when sending x_char
  serial: stm32: fix software flow control transfer

 drivers/tty/serial/stm32-usart.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [PATCH 1/2] serial: stm32: prevent TDR register overwrite when sending x_char
  2022-01-11 16:44 ` Valentin Caron
@ 2022-01-11 16:44   ` Valentin Caron
  -1 siblings, 0 replies; 6+ messages in thread
From: Valentin Caron @ 2022-01-11 16:44 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, Erwan Le Ray,
	Valentin Caron, linux-serial, linux-stm32, linux-arm-kernel,
	linux-kernel

When sending x_char in stm32_usart_transmit_chars(), driver can overwrite
the value of TDR register by the value of x_char. If this happens, the
previous value that was present in TDR register will not be sent through
uart.

This code checks if the previous value in TDR register is sent before
writing the x_char value into register.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
---
 drivers/tty/serial/stm32-usart.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 1f89ab0e49ac..c1b8828451c8 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -550,11 +550,23 @@ static void stm32_usart_transmit_chars(struct uart_port *port)
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
 	struct circ_buf *xmit = &port->state->xmit;
+	u32 isr;
+	int ret;
 
 	if (port->x_char) {
 		if (stm32_usart_tx_dma_started(stm32_port) &&
 		    stm32_usart_tx_dma_enabled(stm32_port))
 			stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT);
+
+		/* Check that TDR is empty before filling FIFO */
+		ret =
+		readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr,
+						  isr,
+						  (isr & USART_SR_TXE),
+						  10, 1000);
+		if (ret)
+			dev_warn(port->dev, "1 character may be erased\n");
+
 		writel_relaxed(port->x_char, port->membase + ofs->tdr);
 		port->x_char = 0;
 		port->icount.tx++;
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH 1/2] serial: stm32: prevent TDR register overwrite when sending x_char
@ 2022-01-11 16:44   ` Valentin Caron
  0 siblings, 0 replies; 6+ messages in thread
From: Valentin Caron @ 2022-01-11 16:44 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, Erwan Le Ray,
	Valentin Caron, linux-serial, linux-stm32, linux-arm-kernel,
	linux-kernel

When sending x_char in stm32_usart_transmit_chars(), driver can overwrite
the value of TDR register by the value of x_char. If this happens, the
previous value that was present in TDR register will not be sent through
uart.

This code checks if the previous value in TDR register is sent before
writing the x_char value into register.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
---
 drivers/tty/serial/stm32-usart.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 1f89ab0e49ac..c1b8828451c8 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -550,11 +550,23 @@ static void stm32_usart_transmit_chars(struct uart_port *port)
 	struct stm32_port *stm32_port = to_stm32_port(port);
 	const struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
 	struct circ_buf *xmit = &port->state->xmit;
+	u32 isr;
+	int ret;
 
 	if (port->x_char) {
 		if (stm32_usart_tx_dma_started(stm32_port) &&
 		    stm32_usart_tx_dma_enabled(stm32_port))
 			stm32_usart_clr_bits(port, ofs->cr3, USART_CR3_DMAT);
+
+		/* Check that TDR is empty before filling FIFO */
+		ret =
+		readl_relaxed_poll_timeout_atomic(port->membase + ofs->isr,
+						  isr,
+						  (isr & USART_SR_TXE),
+						  10, 1000);
+		if (ret)
+			dev_warn(port->dev, "1 character may be erased\n");
+
 		writel_relaxed(port->x_char, port->membase + ofs->tdr);
 		port->x_char = 0;
 		port->icount.tx++;
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH 2/2] serial: stm32: fix software flow control transfer
  2022-01-11 16:44 ` Valentin Caron
@ 2022-01-11 16:44   ` Valentin Caron
  -1 siblings, 0 replies; 6+ messages in thread
From: Valentin Caron @ 2022-01-11 16:44 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, Erwan Le Ray,
	Valentin Caron, linux-serial, linux-stm32, linux-arm-kernel,
	linux-kernel

x_char is ignored by stm32_usart_start_tx() when xmit buffer is empty.

Fix start_tx condition to allow x_char to be sent.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")

Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
---
 drivers/tty/serial/stm32-usart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index c1b8828451c8..9570002d07e7 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -742,7 +742,7 @@ static void stm32_usart_start_tx(struct uart_port *port)
 	struct serial_rs485 *rs485conf = &port->rs485;
 	struct circ_buf *xmit = &port->state->xmit;
 
-	if (uart_circ_empty(xmit))
+	if (uart_circ_empty(xmit) && !port->x_char)
 		return;
 
 	if (rs485conf->flags & SER_RS485_ENABLED) {
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH 2/2] serial: stm32: fix software flow control transfer
@ 2022-01-11 16:44   ` Valentin Caron
  0 siblings, 0 replies; 6+ messages in thread
From: Valentin Caron @ 2022-01-11 16:44 UTC (permalink / raw)
  To: Greg Kroah-Hartman
  Cc: Jiri Slaby, Maxime Coquelin, Alexandre Torgue, Erwan Le Ray,
	Valentin Caron, linux-serial, linux-stm32, linux-arm-kernel,
	linux-kernel

x_char is ignored by stm32_usart_start_tx() when xmit buffer is empty.

Fix start_tx condition to allow x_char to be sent.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")

Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
---
 drivers/tty/serial/stm32-usart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index c1b8828451c8..9570002d07e7 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -742,7 +742,7 @@ static void stm32_usart_start_tx(struct uart_port *port)
 	struct serial_rs485 *rs485conf = &port->rs485;
 	struct circ_buf *xmit = &port->state->xmit;
 
-	if (uart_circ_empty(xmit))
+	if (uart_circ_empty(xmit) && !port->x_char)
 		return;
 
 	if (rs485conf->flags & SER_RS485_ENABLED) {
-- 
2.17.1


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-01-11 16:47 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-01-11 16:44 [PATCH 0/2] serial: stm32: fix software flow control Valentin Caron
2022-01-11 16:44 ` Valentin Caron
2022-01-11 16:44 ` [PATCH 1/2] serial: stm32: prevent TDR register overwrite when sending x_char Valentin Caron
2022-01-11 16:44   ` Valentin Caron
2022-01-11 16:44 ` [PATCH 2/2] serial: stm32: fix software flow control transfer Valentin Caron
2022-01-11 16:44   ` Valentin Caron

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