linux-kernel - Re: [PATCH 2/3] dt-bindings: add binding for at91-usart in spi mode

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Message-ID: <20180417110358.GD8973@sirena.org.uk>
Date:   Tue, 17 Apr 2018 12:03:58 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Radu Pirea <radu.pirea@...rochip.com>, robh+dt@...nel.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/3] dt-bindings: add binding for at91-usart in spi mode

On Fri, Apr 13, 2018 at 08:12:51PM +0200, Alexandre Belloni wrote:
> On 13/04/2018 19:12:54+0200, Nicolas Ferre wrote:

> > This layout of the hardware is completely different from the USART one and
> > it seems to makes sense to address it with a different hardware description
> > and so a different compatible string.

> But then, you can end up with two drivers trying to use the same IP
> because nothing prevents you from writing a DT with both a usart and an
> spi node enabled for the same IP. request_mem_region() will not help
> here because then the working driver will depend on the probing order.

We don't really have too much in the way of better ideas for how to
handle this though.  Take a look at how the PXA SSP stuff handles this,
though that's not really doing too much different it at least layers a
mechanism on top to avoid collisions.

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