linux-kernel - Re: [PATCH 1/2] dt-bindings: spi: Add Spreadtrum SPI controller documentation

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Message-ID: <CAMz4kuKwfBB8-8o5s8FQadFSFiD8KU=qNZYQjCWOfc-QpuVRSw@mail.gmail.com>
Date:   Thu, 9 Aug 2018 11:03:11 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Trent Piepho <tpiepho@...inj.com>
Cc:     "broonie@...nel.org" <broonie@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "orsonzhai@...il.com" <orsonzhai@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "zhang.lyra@...il.com" <zhang.lyra@...il.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "lanqing.liu@...eadtrum.com" <lanqing.liu@...eadtrum.com>
Subject: Re: [PATCH 1/2] dt-bindings: spi: Add Spreadtrum SPI controller documentation

Hi Trent,

On 9 August 2018 at 02:57, Trent Piepho <tpiepho@...inj.com> wrote:
> On Wed, 2018-08-08 at 11:54 +0100, Mark Brown wrote:
>> On Wed, Aug 08, 2018 at 06:35:28PM +0800, Baolin Wang wrote:
>> > On 8 August 2018 at 17:50, Mark Brown <broonie@...nel.org> wrote:
>> > > Right, I don't think we added this yet (if we did I can't see
>> > > it).  I'd
>> > > add a new field to spi_transfer for this, then other controllers
>> > > with
>> > > the same support can implement it as well and drivers can start
>> > > using
>> > > it too.
>> > OK. So I will name the new filed as 'word_delay', is it OK for you?
>>
>> Sounds good, yes.
>
> Should it be in µs like the existing iter-transfer delay?  I think
> perhaps units of cycles of the SPI clock make more sense?

Since some SPI controllers just want some interval values (neither µs
unit nor cycles unit ) set into hardware, and the hardware will
convert to the correct delay time automatically. So I did not force
'word_delay' unit as µs or cycle, and just let the slave devices
decide the unit which depends on the SPI hardware requirement.

-- 
Baolin Wang
Best Regards