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Subject: Re: [PATCH v8 08/10] gpu: host1x: mipi: Keep MIPI clock enabled till
 calibration is done
From:   Sowjanya Komatineni <skomatineni@nvidia.com>
To:     Dmitry Osipenko <digetx@gmail.com>,
        Thierry Reding <thierry.reding@gmail.com>
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On 8/5/20 10:46 AM, Sowjanya Komatineni wrote:
>
> On 8/5/20 10:34 AM, Dmitry Osipenko wrote:
>> 05.08.2020 20:29, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>> ...
>>> UART_FST_MIPI_CAL is the clock used for calibration logic which is FSM
>>> that goes thru sequence codes and when done waits for pads to be in
>>> LP-11 to apply results.
>>>
>>> MIPI_CLK is controller gate clock which is also need to be kept enabled
>>> as incase if it sees LP-11 it updates registers so its recommended to
>>> have this clock enabled.
>>>
>>> We can cancel_calibration() in CSI only when csi/sensor stream on fails
>>> and in which case there will be no LP-11 so we can unconditionally
>>> disable MIPI_CLK.
>>>
>> There is no guarantee that the fail comes before the LP-11. For example,
>> some odd camera driver may have a complicated enable sequence which may
>> fail after enabling the hardware streaming.
>
> MIPI_CLK to keep enable is for calibration logic to update results,=20
> but like I said calibration logic uses UART_FST_MIPI_CAL clock. So=20
> even in case if fail happens from sensor after having pads in LP-11=20
> then, calibration logic will still be running but result update will=20
> not happen with clock disabled. But HW will not stuck as this is=20
> confirmed from HW designer.

If LP-11 happens from sensor stream (followed by fail) and by that time=20
if calibration FSM is done and if calibration logic sees LP-11 then=20
results will be applied to pads.

We did start of calibration before CSI stream so by the time we do=20
sensor stream enable, calibration logic might have done with FSM and=20
waiting for LP-11

Also if we see any special case, we always can use finish_calibration()=20
instead of cancel_calibration() as well.

finish_calibration() has extra 250ms wait time polling done bit and we=20
can ignore its return code during fail pathway.

>
>
>