Re: AW: [PATCH v3] serial: 8250_omap: clear rx_running on zero-length DMA completes

[Moteen Shah <m-shah@ti.com>]

On 22/05/26 14:32, Matthias Feser wrote:
> On AM33xx RX DMA only triggers when the FIFO reaches the
> configured threshold (typically 48 bytes). For smaller bursts
> no DMA request is issued and the FIFO is drained by RX timeout.
>
> In this case __dma_rx_do_complete() can legitimately see count == 0.
>
> The current code exits early in this case and does not clear
> dma->rx_running, leaving the DMA state inconsistent. This can
> prevent RX DMA from restarting and may cause
> omap_8250_rx_dma_flush() to fail, marking DMA as broken.
>
> Fix this by clearing dma->rx_running once the DMA transfer has
> completed or been terminated, even if no data was transferred.
>
> Signed-off-by: Matthias Feser <mfe@KBSgmbhfr.onmicrosoft.com>
> ---
> Changes in v3:
> - Move "Changes in v2" below the tear line as suggested
>
> Changes in v2:
> - Move dma->rx_running clear before the count check so the state
>    is updated immediately after DMA completion/termination
>
>   drivers/tty/serial/8250/8250_omap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> index c552c6b9a037..76bc8ad324cb 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -944,11 +944,11 @@ static void __dma_rx_do_complete(struct uart_8250_port *p)
>   				dev_err(p->port.dev, "teardown incomplete\n");
>   		}
>   	}
> +	dma->rx_running = 0;

Nit: Add a newline above dma->rx_running, I think checkpatch would have 
caught it.
With the above change:
Reviewed-by: Moteen Shah <m-shah@ti.com>

Please pick the tag up in the next version if you intend to make one.

Thanks and Regards,
Moteen

>   	if (!count)
>   		goto out;
>   	ret = tty_insert_flip_string(tty_port, dma->rx_buf, count);
>   
> -	dma->rx_running = 0;
>   	p->port.icount.rx += ret;
>   	p->port.icount.buf_overrun += count - ret;
>   out: