linux-kernel - Re: [PATCH] serial: sh-sci: disable DMA for uart

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Message-ID: <20190513114225.jhd5in7zavd5wvbw@verge.net.au>
Date:   Mon, 13 May 2019 13:42:25 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "George G. Davis" <ggdavisiv@...il.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Chris Brandt <chris.brandt@...esas.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Ulrich Hecht <ulrich.hecht+renesas@...il.com>,
        Andy Lowe <andy_lowe@...tor.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS 
        <devicetree@...r.kernel.org>, Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "George G. Davis" <george_davis@...tor.com>
Subject: Re: [PATCH] serial: sh-sci: disable DMA for uart_console

On Mon, May 13, 2019 at 01:13:16PM +0200, Geert Uytterhoeven wrote:
> Hi George,
> 
> On Thu, May 9, 2019 at 4:44 PM George G. Davis <ggdavisiv@...il.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@...adit-jv.com>
> > Cc: Eugeniu Rosca <erosca@...adit-jv.com>
> > Signed-off-by: George G. Davis <george_davis@...tor.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.

+1

> Anyone else with a comment?

Reviewed-by: Simon Horman <horms+renesas@...ge.net.au>