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@de.adit-jv.com 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 Cc: stable@vger.kernel.org Signed-off-by: George G. Davis george_davis@mentor.com --- v2: Clarify comment regarding DMA support on kernel console, add {Tested,Reviewed}-by:, and Cc: linux-stable lines. --- drivers/tty/serial/sh-sci.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 3cd139752d3f..abc705716aa0 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1557,6 +1557,13 @@ static void sci_request_dma(struct uart_port *port)
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;
Hi George,
On Mon, May 13, 2019 at 5:48 PM George G. Davis george_davis@mentor.com 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.
I don't think this is an appropriate reference, as it points to a patch that was never applied.
As the problem has basically existed forever, IMHO no Fixes tag is needed.
Reported-by: Michael Rodin mrodin@de.adit-jv.com 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 Cc: stable@vger.kernel.org Signed-off-by: George G. Davis george_davis@mentor.com
v2: Clarify comment regarding DMA support on kernel console, add {Tested,Reviewed}-by:, and Cc: linux-stable lines.
Thanks for the update!
Reviewed-by: Geert Uytterhoeven geert+renesas@glider.be
Gr{oetje,eeting}s,
Geert
Hello Geert,
On Tue, May 14, 2019 at 10:28:34AM +0200, Geert Uytterhoeven wrote:
Hi George,
On Mon, May 13, 2019 at 5:48 PM George G. Davis george_davis@mentor.com 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.
I don't think this is an appropriate reference, as it points to a patch that was never applied.
I included it as a link to an upstream problem report similar to other commits that I previewed. The link provides the extra context that I was perhaps to lazy to note in the commit header.
As the problem has basically existed forever,
Agreed
IMHO no Fixes tag is needed.
I've dropped the Fixes line.
Reported-by: Michael Rodin mrodin@de.adit-jv.com 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 Cc: stable@vger.kernel.org Signed-off-by: George G. Davis george_davis@mentor.com
v2: Clarify comment regarding DMA support on kernel console, add {Tested,Reviewed}-by:, and Cc: linux-stable lines.
Thanks for the update!
Thanks!
I'll submit v3 later today.
Reviewed-by: Geert Uytterhoeven geert+renesas@glider.be
Gr{oetje,eeting}s,
Geert-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
I don't think this is an appropriate reference, as it points to a patch that was never applied.
I included it as a link to an upstream problem report similar to other commits that I previewed. The link provides the extra context that I was perhaps to lazy to note in the commit header.
We have a "Link:" tag for things like this, e.g.:
Hello Wolfram,
On Tue, May 14, 2019 at 05:54:51PM +0200, Wolfram Sang wrote:
I don't think this is an appropriate reference, as it points to a patch that was never applied.
I included it as a link to an upstream problem report similar to other commits that I previewed. The link provides the extra context that I was perhaps to lazy to note in the commit header.
We have a "Link:" tag for things like this, e.g.:
Right, I've changed it to a Link instead.
Thanks!
linux-stable-mirror@lists.linaro.org
-
Geert Uytterhoeven -
George G. Davis -
Wolfram Sang