| Message ID | 1557762446-23811-1-git-send-email-george_davis@mentor.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | [v2] serial: sh-sci: disable DMA for uart_console | expand |
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. > > Fixes: https://patchwork.kernel.org/patch/10929511/ 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. > > > > Fixes: https://patchwork.kernel.org/patch/10929511/ > > 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
> > > Fixes: https://patchwork.kernel.org/patch/10929511/ > > > > 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.: Link: https://patchwork.kernel.org/patch/10929511/
Hello Wolfram, On Tue, May 14, 2019 at 05:54:51PM +0200, Wolfram Sang wrote: > > > > > Fixes: https://patchwork.kernel.org/patch/10929511/ > > > > > > 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.: > > Link: https://patchwork.kernel.org/patch/10929511/ Right, I've changed it to a Link instead. Thanks!
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;
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(+)