linux-kernel - Re: [PATCH] serial: sh-sci: Fix receive on SCIFA/SCIFB variants with DMA

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Message-ID: <20181012121908.sbwsojs7vvhiztbb@ninjato>
Date:   Fri, 12 Oct 2018 14:19:08 +0200
From:   Wolfram Sang <wsa@...-dreams.de>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Ulrich Hecht <uli+renesas@...nd.eu>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-serial@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: sh-sci: Fix receive on SCIFA/SCIFB variants with
 DMA

On Tue, Oct 09, 2018 at 07:41:58PM +0200, Geert Uytterhoeven wrote:
> On SCIFA and SCIFB serial ports with DMA support (i.e. some ports on
> R-Car Gen2 and RZ/G1 SoCs), receive DMA operations are submitted before
> the DMA channel pointer is initialized.  Hence this fails, and the
> driver tries to fall back to PIO.  However, at this early phase in the
> initialization sequence, fallback to PIO does not work, leading to a
> serial port that cannot receive any data.
> 
> Fix this by calling sci_submit_rx() after initialization of the DMA
> channel pointer.
> 
> Reported-by: Jinzai Solution and RVC Test Teams via Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>

Brainstorming: keep Shimoda-san's address as is and mention the test
teams in the commit message?

> Fixes: 2c4ee23530ffc022 ("serial: sh-sci: Postpone DMA release when falling back to PIO")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Reviewed-by: Wolfram Sang <wsa+renesas@...g-engineering.com>

> ---
> Reported on r8a7790/lager using SCIFA1 on Debug Serial 1.

I hope to test this on Lager this weekend. I am quite sure it will work
now, but then we have this formally checked, too.

> Tested on r8a7791/koelsch using SCIFA3 on EXIO-B.

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