linux-kernel - Re: [PATCH 0/3] mtd: spi-nor: fix DMA-unsafe buffer issue between MTD and SPI

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Message-ID: <20171227103609.GQ1827@finisterre>
Date:   Wed, 27 Dec 2017 10:36:09 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Trent Piepho <tpiepho@...inj.com>
Cc:     "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "cyrille.pitchen@...ev4u.fr" <cyrille.pitchen@...ev4u.fr>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "boris.brezillon@...e-electrons.com" 
        <boris.brezillon@...e-electrons.com>,
        "vigneshr@...com" <vigneshr@...com>,
        "richard@....at" <richard@....at>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "radu.pirea@...rochip.com" <radu.pirea@...rochip.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 0/3] mtd: spi-nor: fix DMA-unsafe buffer issue between
 MTD and SPI

On Tue, Dec 26, 2017 at 06:45:28PM +0000, Trent Piepho wrote:

> Or, since this only fixes instances of DMA-unsafe buffers used in
> access to SPI NOR flash chips, and since there are other SPI master
> interface users, those chip specific fixes in some/all spi master
> drivers are still needed to fix transfers not originated via spi-nor? 

SPI client drivers are *supposed* to use DMA safe memory already.  How
often that happens in cases where it matters is a separate question, we
definitely have users with smaller transfers that don't do the right
thing but they're normally done using PIO anyway.

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