linux-kernel - Re: spi-mem and gpio chipselects

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Message-ID: <20191104124444.GB5238@sirena.co.uk>
Date:   Mon, 4 Nov 2019 12:44:44 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: spi-mem and gpio chipselects

On Mon, Nov 04, 2019 at 12:35:24AM +0000, Chris Packham wrote:

> I'm working on a platform that has a slightly complicated scheme for
> SPI chip-selects using gpios[1]. The spi controller driver in this case
> supports the spi-mem operations which appear to bypass the generic
> spi_set_cs().

> Would there be any harm in adding calls to spi_set_cs() to spi-mem.c?
> Naively spi_mem_access_start() and spi_mem_access_end() seem like
> convenient places to start.

That's only going to work in cases where the controller translates
things into a single SPI operation on the flash which I'm not sure is
always going to be the case.  We'd need a way to guarantee that the
controller is going to do that in order to avoid data corruption issues.

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