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From: Geert Uytterhoeven <geert@linux-m68k.org>
To: "George G. Davis" <ggdavisiv@gmail.com>
Cc: Eugeniu Rosca <erosca@de.adit-jv.com>,
	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 13:13:16 +0200	[thread overview]
Message-ID: <CAMuHMdUCcxfVdY1PqfYRZMjHN2eP_-NAsniCY39XyrDysAu1Pw@mail.gmail.com> (raw)
In-Reply-To: <1557413011-1662-1-git-send-email-george_davis@mentor.com>

Hi George,

On Thu, May 9, 2019 at 4:44 PM George G. Davis <ggdavisiv@gmail.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/
> 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>

I think this makes sense.  In addition to OMAP 8250, the same approach
is used in the Mediatek 8250 and iMX serial drivers.

Regardless, this is definitely better than removing the "dmas" properties
from DT, as DT describes hardware, not usage policies.

Anyone else with a comment?

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

  parent reply	other threads:[~2019-05-13 11:13 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 [this message]
2019-05-13 11:42           ` Simon Horman
2019-05-13 13:51         ` Wolfram Sang
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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