linux-kernel - Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till calibration is done

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Message-ID: <eddfdaf0-818a-c4dd-e3b4-4d432af56982@nvidia.com>
Date:   Thu, 6 Aug 2020 11:07:21 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>
CC:     <jonathanh@...dia.com>, <frankc@...dia.com>, <hverkuil@...all.nl>,
        <sakari.ailus@....fi>, <robh+dt@...nel.org>,
        <helen.koike@...labora.com>, <gregkh@...uxfoundation.org>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till
 calibration is done


On 8/6/20 11:01 AM, Dmitry Osipenko wrote:
> 06.08.2020 20:52, Sowjanya Komatineni пишет:
> ...
>> Right mutex_unlock should happen at end of finish_calibration.
>>
>> With keeping mutex locked in start, we dont have to check for active to
>> be 0 to issue start as mutex will keep it locked and other pads
>> calibration can only go thru when current one is done.
>>
>> So instead of below sequence, its simpler to do this way?
>>
>> start_calibration()
>>
>> - mutex_lock
>>
>> - wait for 72uS after start
>>
>> finish_calibration()
>>
>> - keep check for ACTIVE = 0 and DONE = 1
> I think only the DONE bits which correspond to the mipi_device->pads
> bitmask should be awaited.

As next START can't be triggered when auto cal is ACTIVE, we should keep 
this in finish.

As we do mutex_unlock only at end of finish, other pads calibrations 
dont go thru till the one in process is finished.

So in this case ACTIVE applies to current selected pads that are under 
calibration.

>
>> - mutex_unlock()
> Perhaps the start_calibration() also needs to be changed to not touch
> the MIPI_CAL_CONFIG bits of the unrelated pads?
Driver already takes care of programming corresponding pads config only.
>
> Otherwise sounds good to me.