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

From: Dmitry Osipenko <digetx@gmail.com>
To: Sowjanya Komatineni <skomatineni@nvidia.com>,
	Thierry Reding <thierry.reding@gmail.com>
Cc: jonathanh@nvidia.com, frankc@nvidia.com, hverkuil@xs4all.nl,
	sakari.ailus@iki.fi, robh+dt@kernel.org,
	helen.koike@collabora.com, gregkh@linuxfoundation.org,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till calibration is done
Date: Thu, 6 Aug 2020 19:10:51 +0300	[thread overview]
Message-ID: <b5612e93-f1c4-4762-baa1-5d85eb1edbe1@gmail.com> (raw)
In-Reply-To: <4f15d655-3d62-cf9f-82da-eae379d60fa6@nvidia.com>

06.08.2020 18:59, Sowjanya Komatineni пишет:
...
>>> Confirmed from HW designer, calibration FSM to finish takes worst case
>>> 72uS so by the time it gets to sensor stream it will be done its
>>> sequence and will be waiting for DONE bit.
>>>
>>> So disabling MIPI CAL clock on sensor stream fails is safe.
>>
>> 72us is quite a lot of time, what will happen if LP-11 happens before
>> FSM finished calibration?
>>
>> Maybe the finish_calibration() needs to split into two parts:
>>
>>   1. wait for CAL_STATUS_ACTIVE before enabling sensor
>>   2. wait for CAL_STATUS_DONE after enabling sensor
> 
> I don't think we need to split for active and done. Active will be 1 as
> long as other pads are in calibration as well.
> 
> We cant use active status check for specific pads under calibration.
> This is common bit for all pads.

Does hardware have a single FSM block shared by all pads or there is FSM
per group of pads?

> Unfortunately HW don't have separate status indicating when sequence is
> done to indicate its waiting for LP11.
> 
> 
> To avoid all this, will remove cancel_calibration() totally and use same
> finish calibration even in case of stream failure then.
> 

What about to add 72us delay to the end of start_calibration() in order
to ensure that FSM is finished before LP-11?