From: Wolfram Sang <wsa@the-dreams.de>
To: "George G. Davis" <ggdavisiv@gmail.com>
Cc: Eugeniu Rosca <erosca@de.adit-jv.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>,
"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
Simon Horman <horms+renesas@verge.net.au>,
Chris Brandt <chris.brandt@renesas.com>,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
Ulrich Hecht <ulrich.hecht+renesas@gmail.com>,
Andy Lowe <andy_lowe@mentor.com>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS
<devicetree@vger.kernel.org>, Magnus Damm <magnus.damm@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
"George G. Davis" <george_davis@mentor.com>
Subject: Re: [PATCH] serial: sh-sci: disable DMA for uart_console
Date: Mon, 13 May 2019 15:51:14 +0200 [thread overview]
Message-ID: <20190513135114.GA20443@kunai> (raw)
In-Reply-To: <1557413011-1662-1-git-send-email-george_davis@mentor.com>
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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@de.adit-jv.com>
> Cc: Eugeniu Rosca <erosca@de.adit-jv.com>
> Signed-off-by: George G. Davis <george_davis@mentor.com>
> ---
> 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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next prev parent reply other threads:[~2019-05-13 13:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-04 0:42 [PATCH 0/6] Zap SCIF2 DMA configuration in R-Car Gen3 DTS Eugeniu Rosca
2019-05-04 0:42 ` [PATCH 1/6] serial: sh-sci: Reveal ptrval in dev_dbg Eugeniu Rosca
2019-05-06 13:47 ` Simon Horman
2019-05-06 15:24 ` Eugeniu Rosca
2019-05-06 16:46 ` Geert Uytterhoeven
2019-05-06 17:12 ` Eugeniu Rosca
2019-05-04 0:42 ` [PATCH 2/6] Revert "arm64: dts: renesas: r8a7796: Enable DMA for SCIF2" Eugeniu Rosca
2019-05-06 10:02 ` Geert Uytterhoeven
2019-05-06 19:42 ` Eugeniu Rosca
[not found] ` <1557413011-1662-1-git-send-email-george_davis@mentor.com>
2019-05-10 17:10 ` [PATCH] serial: sh-sci: disable DMA for uart_console Eugeniu Rosca
2019-05-10 18:38 ` George G. Davis
2019-05-13 10:28 ` Eugeniu Rosca
2019-05-13 11:13 ` Geert Uytterhoeven
2019-05-13 11:42 ` Simon Horman
2019-05-13 13:51 ` Wolfram Sang [this message]
2019-05-13 15:43 ` George G. Davis
2019-05-20 2:18 ` [PATCH 2/6] Revert "arm64: dts: renesas: r8a7796: Enable DMA for SCIF2" Yoshihiro Shimoda
2019-05-20 7:37 ` Geert Uytterhoeven
2019-05-20 9:52 ` Yoshihiro Shimoda
2019-05-04 0:42 ` [PATCH 3/6] arm64: dts: renesas: r8a7795: zap dma configuration in scif2 Eugeniu Rosca
2019-05-04 0:42 ` [PATCH 4/6] Revert "arm64: dts: renesas: r8a77965: Enable DMA for SCIF2" Eugeniu Rosca
2019-05-04 0:42 ` [PATCH 5/6] Revert "arm64: dts: renesas: r8a77990: " Eugeniu Rosca
2019-05-04 0:42 ` [PATCH 6/6] Revert "arm64: dts: renesas: r8a77995: add " Eugeniu Rosca
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