Re: [PATCH] serial: sh-sci: disable DMA for uart_console
From: Wolfram Sang <hidden>
Date: 2019-05-13 13:51:19
Also in:
linux-devicetree, linux-renesas-soc, lkml
On Thu, May 09, 2019 at 10:43:30AM -0400, George G. Davis wrote:
quoted hunk
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 <redacted> Cc: Eugeniu Rosca <redacted> Signed-off-by: George G. Davis <redacted> --- 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@sang-engineering.com> Much better than dropping the properties, as Geert noted.
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