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Subject: Re: [RFC PATCH v5 13/14] media: tegra-video: Add CSI MIPI pads
 calibration
From:   Sowjanya Komatineni <skomatineni@nvidia.com>
To:     Dmitry Osipenko <digetx@gmail.com>, <thierry.reding@gmail.com>,
        <jonathanh@nvidia.com>, <frankc@nvidia.com>, <hverkuil@xs4all.nl>,
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On 7/28/20 8:59 AM, Sowjanya Komatineni wrote:
>
> On 7/28/20 3:30 AM, Dmitry Osipenko wrote:
>> 27.07.2020 23:57, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>> +=C2=A0=C2=A0=C2=A0 /*
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * TRM has incorrectly documented to wait for =
done status from
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * calibration logic after CSI interface power=
 on.
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * As per the design, calibration results are =
latched and applied
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * to the pads only when the link is in LP11 s=
tate which will=20
>>> happen
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * during the sensor stream-on.
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * CSI subdev stream-on triggers start of MIPI=
 pads calibration.
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * Wait for calibration to finish here after s=
ensor subdev=20
>>> stream-on
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 * and in case of sensor stream-on failure, ca=
ncel the=20
>>> calibration.
>>> +=C2=A0=C2=A0=C2=A0=C2=A0 */
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 subdev =3D on ? src_subdev : csi_subdev;
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D v4l2_subdev_call(subdev, video, =
s_stream, on);
>>> -=C2=A0=C2=A0=C2=A0 if (ret < 0 && ret !=3D -ENOIOCTLCMD)
>>> +=C2=A0=C2=A0=C2=A0 if (ret < 0 && ret !=3D -ENOIOCTLCMD) {
>> I assume -ENOIOCTLCMD means that camera wasn't turned ON, so why
>> -ENOIOCTLCMD is special?
> No -ENOIOCTLCMD mean subdev don't have s_stream ops
>>
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (on && csi_chan->mipi)
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 teg=
ra_mipi_cancel_calibration(csi_chan->mipi);
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return ret;
>>> +=C2=A0=C2=A0=C2=A0 }
>>> +
>>> +=C2=A0=C2=A0=C2=A0 if (on && csi_chan->mipi) {
>> Does finish_calibration() really need to be called for ret=3D-ENOIOCTLCM=
D?
>>
>> Shouldn't it be cancel_calibration( for the -ENOIOCTLCMD?
>
> start calibration happens during csi sensor streaming which happens=20
> prior to this point.
>
> In case if sensor subdev does not have s_stream ops, then either=20
> finish/cancel calibration should happen to disable the clock.

For -ENOIOCTLCMD, calling finish calibration as some sensors might keep=20
pads in LP-11 on power up and for such sensors calibration logic will=20
apply results to pads and done bit will be set.

Also avoiding additional check to specifically call cancel calibration=20
on ENOIOCTLCMD and making it fall into finish calibration as both does=20
disable clock except finish will wait for done bit to be set.

Also, most sensor subdev have s_stream ops implemented.

>
>>
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D tegra_mipi_finish_c=
alibration(csi_chan->mipi);
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (ret < 0)
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dev=
_err(csi_chan->csi->dev,
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 "MIPI calibration failed: %d\n", ret);
>> Doesn't v4l2_subdev_call(OFF) need to be invoked here on error?
>
> Not required as on error streaming fails and runtime PM will turn off=20
> power anyway.
>
> Also we only did csi subdev s_stream on and during sensor subdev=20
> s_stream on fail, actual stream dont happen and on tegra side frame=20
> capture by HW happens only when kthreads run.
>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return ret;
>>> +=C2=A0=C2=A0=C2=A0 }
>>> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return 0;
>>> =C2=A0 }