linux-kernel - Re: [PATCH v2 4/6] dmaengine: dw: Print warning if multi-block is unsupported

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Message-ID: <20200511115813.GG8216@sirena.org.uk>
Date:   Mon, 11 May 2020 12:58:13 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Vinod Koul <vkoul@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, linux-mips@...r.kernel.org,
        devicetree@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/6] dmaengine: dw: Print warning if multi-block is
 unsupported

On Mon, May 11, 2020 at 05:10:16AM +0300, Serge Semin wrote:

> Alas linearizing the SPI messages won't help in this case because the DW DMA
> driver will split it into the max transaction chunks anyway.

That sounds like you need to also impose a limit on the maximum message
size as well then, with that you should be able to handle messages up
to whatever that limit is.  There's code for that bit already, so long
as the limit is not too low it should be fine for most devices and
client drivers can see the limit so they can be updated to work with it
if needed.

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