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[PATCH v2] serial: imx: Introduce timeout when waiting on transmitter empty

Esben Haabendal posted 1 patch 1 year, 10 months ago
There is a newer version of this series
drivers/tty/serial/imx.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
[PATCH v2] serial: imx: Introduce timeout when waiting on transmitter empty
Posted by Esben Haabendal 1 year, 10 months ago 
By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
deadlock.

In case of the timeout, there is not much we can do, so we simply ignore
the transmitter state and optimistically try to continue.

v2:
- Fixed commit message typo
- Remove reference to patch series it originated from. This is a
  stand-alone patch

Signed-off-by: Esben Haabendal <esben@geanix.com>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/tty/serial/imx.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index e14813250616..09c1678ddfd4 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -26,6 +26,7 @@
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/dma-mapping.h>
 
 #include <asm/irq.h>
@@ -2010,7 +2011,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
 	struct imx_port *sport = imx_uart_ports[co->index];
 	struct imx_port_ucrs old_ucr;
 	unsigned long flags;
-	unsigned int ucr1;
+	unsigned int ucr1, usr2;
 	int locked = 1;
 
 	if (sport->port.sysrq)
@@ -2041,8 +2042,8 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
 	 *	Finally, wait for transmitter to become empty
 	 *	and restore UCR1/2/3
 	 */
-	while (!(imx_uart_readl(sport, USR2) & USR2_TXDC));
-
+	read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC,
+				 0, USEC_PER_SEC, false, sport, USR2);
 	imx_uart_ucrs_restore(sport, &old_ucr);
 
 	if (locked)
-- 
2.44.0
Re: [PATCH v2] serial: imx: Introduce timeout when waiting on transmitter empty
Posted by Greg Kroah-Hartman 1 year, 10 months ago 
On Wed, Apr 10, 2024 at 09:18:32AM +0200, Esben Haabendal wrote:
> By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
> deadlock.
> 
> In case of the timeout, there is not much we can do, so we simply ignore
> the transmitter state and optimistically try to continue.
> 
> v2:
> - Fixed commit message typo
> - Remove reference to patch series it originated from. This is a
>   stand-alone patch

The "v2:" stuff needs to go below the --- line, so it doesn't show up in
the kernel changelog.  The kernel documentation should describe this,
right?

Please fix up and send a v3.

thanks,

greg k-h
Re: [PATCH v2] serial: imx: Introduce timeout when waiting on transmitter empty
Posted by Esben Haabendal 1 year, 10 months ago 
Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:

> On Wed, Apr 10, 2024 at 09:18:32AM +0200, Esben Haabendal wrote:
>> By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
>> deadlock.
>> 
>> In case of the timeout, there is not much we can do, so we simply ignore
>> the transmitter state and optimistically try to continue.
>> 
>> v2:
>> - Fixed commit message typo
>> - Remove reference to patch series it originated from. This is a
>>   stand-alone patch
>
> The "v2:" stuff needs to go below the --- line, so it doesn't show up in
> the kernel changelog.  The kernel documentation should describe this,
> right?

Right. It is described in Documentation/process/submitting-patches.rst.
Sorry about that.

> Please fix up and send a v3.

On its way.

/Esben
[PATCH v3] serial: imx: Introduce timeout when waiting on transmitter empty
Posted by Esben Haabendal 1 year, 10 months ago 
By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
deadlock.

In case of the timeout, there is not much we can do, so we simply ignore
the transmitter state and optimistically try to continue.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
---

v2:
- Fixed commit message typo
- Remove reference to patch series it originated from. This is a
  stand-alone patch

v3:
- Moved this version information into the correct patch section

 drivers/tty/serial/imx.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index e14813250616..09c1678ddfd4 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -26,6 +26,7 @@
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/dma-mapping.h>
 
 #include <asm/irq.h>
@@ -2010,7 +2011,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
 	struct imx_port *sport = imx_uart_ports[co->index];
 	struct imx_port_ucrs old_ucr;
 	unsigned long flags;
-	unsigned int ucr1;
+	unsigned int ucr1, usr2;
 	int locked = 1;
 
 	if (sport->port.sysrq)
@@ -2041,8 +2042,8 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
 	 *	Finally, wait for transmitter to become empty
 	 *	and restore UCR1/2/3
 	 */
-	while (!(imx_uart_readl(sport, USR2) & USR2_TXDC));
-
+	read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC,
+				 0, USEC_PER_SEC, false, sport, USR2);
 	imx_uart_ucrs_restore(sport, &old_ucr);
 
 	if (locked)
-- 
2.44.0
Re: [PATCH v3] serial: imx: Introduce timeout when waiting on transmitter empty
Posted by Esben Haabendal 1 year, 9 months ago 
Esben Haabendal <esben@geanix.com> writes:

> By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
> deadlock.
>
> In case of the timeout, there is not much we can do, so we simply ignore
> the transmitter state and optimistically try to continue.
>
> Signed-off-by: Esben Haabendal <esben@geanix.com>
> Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
>
> v2:
> - Fixed commit message typo
> - Remove reference to patch series it originated from. This is a
>   stand-alone patch
>
> v3:
> - Moved this version information into the correct patch section

Anything more needed in order to get this merged?

/Esben

>
>  drivers/tty/serial/imx.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index e14813250616..09c1678ddfd4 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -26,6 +26,7 @@
>  #include <linux/slab.h>
>  #include <linux/of.h>
>  #include <linux/io.h>
> +#include <linux/iopoll.h>
>  #include <linux/dma-mapping.h>
>  
>  #include <asm/irq.h>
> @@ -2010,7 +2011,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
>  	struct imx_port *sport = imx_uart_ports[co->index];
>  	struct imx_port_ucrs old_ucr;
>  	unsigned long flags;
> -	unsigned int ucr1;
> +	unsigned int ucr1, usr2;
>  	int locked = 1;
>  
>  	if (sport->port.sysrq)
> @@ -2041,8 +2042,8 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
>  	 *	Finally, wait for transmitter to become empty
>  	 *	and restore UCR1/2/3
>  	 */
> -	while (!(imx_uart_readl(sport, USR2) & USR2_TXDC));
> -
> +	read_poll_timeout_atomic(imx_uart_readl, usr2, usr2 & USR2_TXDC,
> +				 0, USEC_PER_SEC, false, sport, USR2);
>  	imx_uart_ucrs_restore(sport, &old_ucr);
>  
>  	if (locked)
Re: [PATCH v3] serial: imx: Introduce timeout when waiting on transmitter empty
Posted by Greg Kroah-Hartman 1 year, 9 months ago 
On Thu, May 02, 2024 at 11:14:26AM +0200, Esben Haabendal wrote:
> Esben Haabendal <esben@geanix.com> writes:
> 
> > By waiting at most 1 second for USR2_TXDC to be set, we avoid a potential
> > deadlock.
> >
> > In case of the timeout, there is not much we can do, so we simply ignore
> > the transmitter state and optimistically try to continue.
> >
> > Signed-off-by: Esben Haabendal <esben@geanix.com>
> > Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>
> > ---
> >
> > v2:
> > - Fixed commit message typo
> > - Remove reference to patch series it originated from. This is a
> >   stand-alone patch
> >
> > v3:
> > - Moved this version information into the correct patch section
> 
> Anything more needed in order to get this merged?

Sorry, but I don't see this in my review queue anymore.  If this isn't
already accepted, please resend it, sorry about that.

greg k-h

Patchew 2.1-devel-b67e4c2

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