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

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Date:   Sat, 26 Jan 2019 08:52:29 +0100
From:   Jonas Bonn <jonas@...rbonn.se>
To:     Mark Brown <broonie@...nel.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 25/01/2019 18:50, Mark Brown wrote:
> On Fri, Jan 25, 2019 at 05:47:13PM +0000, Mark Brown wrote:
>> On Fri, Jan 25, 2019 at 01:06:45PM +0100, Jonas Bonn wrote:
> 
>>> Having this as device property rather than a transfer property allows this
>>> to be configured one time in setup() rather than having to fiddle with the
>>> configuration register for every transfer.
> 
>> That doesn't mean that the coniguration should be done in DT though, and
>> given that this presumably is a property of the device there seems to be
>> no reason why we'd have it in DT - if every instance of the device is
>> going to need to set the property we should just figure it out from the
>> compatble string instead.
> 
> To be clear here: the suggestion is to add a parameter the slave device
> can set in spi_device which sets the default word_delay similarly to how
> max_speed_hz works.
> 

I'm confused... isn't that exactly what this patch does?  It adds a 
field word_delay to spi_device in the same manner as max_speed_hz.

I also added the ability to set it via DT, which I can break out into a 
separate patch if that's an issue.  Or is the problem that it's set via 
DT, at all?  Documentation/devicetree/bindings/spi-bus.txt documents 10 
other slave-node properties related to transfer characteristics; 
word_delay is just another such characteristic.

But again, I'm having trouble parsing your response  Is the patch wrong, 
should be broken up, or you just misunderstood it?

Thanks,
/Jonas