Re: [PATCH] serial: imx: reduce RX interrupt frequency

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 04.01.22 11:32, Tomasz Moń wrote:
> Triggering RX interrupt for every byte defeats the purpose of aging
> timer and leads to interrupt starvation at high baud rates.

s/starvation/storm/ ?

> 
> Increase receiver trigger level to 8 to increase the minimum period
> between RX interrupts to 8 characters time. The tradeoff is increased
> latency. In the worst case scenario, where RX data has intercharacter
> delay slightly less than aging timer (8 characters time), it can take
> up to 63 characters time for the interrupt to be raised since the
> reception of the first character.
> 
> Signed-off-by: Tomasz Moń <tomasz.mon@camlingroup.com>
> ---
>  drivers/tty/serial/imx.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 90f82e6c54e4..3c812c47ecc0 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1255,7 +1255,7 @@ static void imx_uart_clear_rx_errors(struct imx_port *sport)
>  }
>  
>  #define TXTL_DEFAULT 2 /* reset default */
> -#define RXTL_DEFAULT 1 /* reset default */
> +#define RXTL_DEFAULT 8 /* 8 characters or aging timer */
>  #define TXTL_DMA 8 /* DMA burst setting */
>  #define RXTL_DMA 9 /* DMA burst setting */
>  
> 


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