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    Subject[PATCH 4.14 56/69] serial: sh-sci: disable DMA for uart_console
    Date
    From: George G. Davis <george_davis@mentor.com>

    commit 099506cbbc79c0bd52b19cb6b930f256dabc3950 upstream.

    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.

    Reported-by: Michael Rodin <mrodin@de.adit-jv.com>
    Link: https://patchwork.kernel.org/patch/10929511/
    Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
    Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
    Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
    Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
    Cc: stable@vger.kernel.org
    Signed-off-by: George G. Davis <george_davis@mentor.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/tty/serial/sh-sci.c | 7 +++++++
    1 file changed, 7 insertions(+)

    --- a/drivers/tty/serial/sh-sci.c
    +++ b/drivers/tty/serial/sh-sci.c
    @@ -1479,6 +1479,13 @@ static void sci_request_dma(struct uart_

    dev_dbg(port->dev, "%s: port %d\n", __func__, port->line);

    + /*
    + * DMA on console may interfere with Kernel log messages which use
    + * plain putchar(). So, simply don't use it with a console.
    + */
    + if (uart_console(port))
    + return;
    +
    if (!port->dev->of_node)
    return;


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