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

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Date:   Thu, 6 Aug 2020 20:15:31 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.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

06.08.2020 19:51, Sowjanya Komatineni пишет:
>>>> What about to add 72us delay to the end of start_calibration() in order
>>>> to ensure that FSM is finished before LP-11?
>>> Why we should add 72uS in start_calibration() when can use same
>>> finish_calibration() for both pass/fail cases?
>>>
>>> Only timing loose we see is in case of failure we still wait for 250ms
>>> and as this is failing case I hope should be ok.
>>>
>> You said that calibration settings are applied to pads on LP-11, but if
>> LP-11 happens before FSM is finished, then what values will be applied
>> if any?
> 
> No calibration logic will check for LP-11 only after finishing
> calibration sequence codes.
> 
> After that if it sees LP-11, it will apply results to pads and DONE bit
> will then be set to 1 indication pad results update.

Are you sure that HW doesn't use level-triggered logic for LP-11 signal?

> Unfortunately like I said we don't have status indication for
> calibrating finished before waiting for LP-11.

This is not a problem if hardware can cope with LP-11 happened at the
time of calibration. If hardware can't cope with that, then somethings
needs to be done about it.