linux-kernel - Re: [PATCH 1/2] spi: support inter-word delay requirement for devices

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Message-ID: <94c7514c-de1f-ff70-d2b7-6394f9747942@norrbonn.se>
Date:   Mon, 28 Jan 2019 12:51:02 +0100
From:   Jonas Bonn <jonas@...rbonn.se>
To:     Mark Brown <broonie@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Baolin Wang <baolin.wang@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/2] spi: support inter-word delay requirement for devices



On 28/01/2019 12:47, Mark Brown wrote:
> On Mon, Jan 28, 2019 at 08:41:05AM +0100, Geert Uytterhoeven wrote:
>> On Sat, Jan 26, 2019 at 4:40 PM Jonas Bonn <jonas@...rbonn.se> wrote:
> 
>>> spi-3wire: again, only set by MAXIM DS-1302 which always needs this
>>> setting; driver could set this
> 
>> For DS1302, this is probable true.
>> Some devices may support both 4-wire or 3-wire mode?
> 
> IIRC yes.

Just for the record, the datasheet says it's exclusively 3-wire.  But 
it's not important...

/Jonas

> 
>>> Yeah, that one make sense.  But if the DT is only overriding the maximum
>>> device frequency that the driver should otherwise be setting, why is
>>> spi-max-frequency a _required_ property?
> 
>> That's a good question. Legacy?
> 
> It's a documentation error.
>