linux-kernel - Re: [PATCH] Revert "spi: modify set_cs

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Date:   Thu, 30 Sep 2021 14:36:01 +0200
From:   Dafna Hirschfeld <dafna.hirschfeld@...labora.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     kernel@...labora.com, linux-spi@...r.kernel.org,
        enric.balletbo@...labora.com, dafna3@...il.com,
        Mason Zhang <Mason.Zhang@...iatek.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, wsd_upstream@...iatek.com,
        Matthias Brugger <matthias.bgg@...il.com>
Subject: Re: [PATCH] Revert "spi: modify set_cs_timing parameter"

hi, thanks for the fast feedback

On 30.09.21 14:25, Mark Brown wrote:
> On Thu, Sep 30, 2021 at 02:07:00PM +0200, Dafna Hirschfeld wrote:
>> This reverts commit 04e6bb0d6bb127bac929fb35edd2dd01613c9520.
> 
> Please submit patches using subject lines reflecting the style for the
> subsystem, this makes it easier for people to identify relevant patches.
> Look at what existing commits in the area you're changing are doing and
> make sure your subject lines visually resemble what they're doing.
> There's no need to resubmit to fix this alone.
> 
>> This revert the commit 'spi: modify set_cs_timing parameter'
>> and its following commit
>> 'spi: mediatek: fix build warnning in set cs timing'.
> 
> Which is not what the commit message nor the paste of the full hash
> claimed :/

What is the paste of the full hash?
Since the second commit is only a warning fixes I thought it is cumbersome to
send two separate reverting patches. Should I?

> 
>> Those commits cause regression on mt8173 elm device. The EC either is not
>> able to register or it sends numerous amount of errors:
> 
>> cros-ec-i2c-tunnel 1100a000.spi:ec@0:i2c-tunnel0: Error transferring EC i2c message -71
>> cros-ec-spi spi0.0: EC failed to respond in time.
> 
> Do we have any analysis as to why?  Do these devices use timing
> parameters in some way for example, or do the values written out to the
> device change in some way?
> 
> You've provided no analysis here so it's hard to tell if this is just
> some random change that happens to change code generation slighly or if
> there's some actual reason why this might fix something.  I'll note that
> as far as I can see there are no users of this API upstream so I'm
> guessing that you've got some out of tree consumer driver which uses the
> API, it's possible that there was some error in updating that driver to
> the new interface which is causing the issue.

Actually the original commit not only change that callback 'set_cs_timing' but it also
calls 'mtk_spi_set_hw_cs_timing' directly from the function "mtk_spi_prepare_message".
So this actually influences all devices bound to this driver (in upstream)
I did some printing and it does change values that are written to registers.

Thanks,
Dafna


>