On Thu, May 09, 2019 at 10:43:30AM -0400, George G. Davis wrote:
> As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for
> console UART"), UART console lines use low-level PIO only access functions
> which will conflict with use of the line when DMA is enabled, e.g. when
> the console line is also used for systemd messages. So disable DMA
> support for UART console lines.
>
> Fixes: https://patchwork.kernel.org/patch/10929511/
> Reported-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> Cc: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
> Signed-off-by: George G. Davis <george_davis@xxxxxxxxxx>
> ---
> drivers/tty/serial/sh-sci.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
> index 3cd139752d3f..885b56b1d4e4 100644
> --- a/drivers/tty/serial/sh-sci.c
> +++ b/drivers/tty/serial/sh-sci.c
> @@ -1557,6 +1557,9 @@ static void sci_request_dma(struct uart_port *port)
>
> dev_dbg(port->dev, "%s: port %d\n", __func__, port->line);
>
> + if (uart_console(port))
> + return; /* Cannot use DMA on console */
Minor nit: maybe the comment can be made more specific?
/*
* DMA on console may interfere with Kernel log messages which use
* plain putchar(). So, simply don't use it with a console.
*/
Other than that:
Reviewed-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Much better than dropping the properties, as Geert noted.
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