Re: [RFC PATCH v2 1/2] serial: imx: Introduce timeout when waiting on transmitter empty

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On 05.04.2024 09:56:37, Esben Haabendal wrote:
> By waiting at most 1 second for USR2_TXDC to be set, we avoid a potentital
> 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@xxxxxxxxxx>

For the next round you should consult "scripts/get_maintainer.pl
drivers/tty/serial/imx.c" and add these people/lists on Cc.

> ---
>  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 54b760d845c0..f7e4f38f08f3 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>
> @@ -1995,7 +1996,7 @@ 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)
> @@ -2026,8 +2027,8 @@ 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, 1000000, false, sport, USR2);

You can make use of USEC_PER_SEC here.

After fixing this, feel free to add my:

Acked-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>

>  	imx_uart_ucrs_restore(sport, &old_ucr);
>  
>  	if (locked)
> -- 
> 2.44.0
> 
> 

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
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