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Subject: Re: [RFC PATCH v6 09/10] media: tegra-video: Add CSI MIPI pads
 calibration
To:     Dmitry Osipenko <digetx@gmail.com>, <thierry.reding@gmail.com>,
        <jonathanh@nvidia.com>, <frankc@nvidia.com>, <hverkuil@xs4all.nl>,
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From:   Sowjanya Komatineni <skomatineni@nvidia.com>
Message-ID: <27ba10cc-21b2-845d-2ed1-a10e89f85d19@nvidia.com>
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On 7/31/20 1:42 PM, Dmitry Osipenko wrote:
> 31.07.2020 19:29, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>> On 7/31/20 9:14 AM, Dmitry Osipenko wrote:
>>> 31.07.2020 18:46, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>> On 7/31/20 4:39 AM, Dmitry Osipenko wrote:
>>>>> 31.07.2020 12:02, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>>> ...
>>>>>> @@ -249,13 +249,47 @@ static int tegra_csi_enable_stream(struct
>>>>>> v4l2_subdev *subdev)
>>>>>>  =C2=A0=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 }
>>>>>>  =C2=A0=C2=A0 +=C2=A0=C2=A0=C2=A0 if (csi_chan->mipi) {
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ret =3D tegra_mipi_enabl=
e(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->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 "failed to enable MIPI pads: %d\n", ret);
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 =
goto rpm_put;
>>>>>> +=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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * CSI MIPI pads PU=
LLUP, PULLDN and TERM impedances need to
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * be calibrated af=
ter power on.
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * So, trigger the =
calibration start here and results will
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * be latched and a=
pplied to the pads when link is in LP11
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * state during sta=
rt of sensor streaming.
>>>>>> +=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 ret =3D tegra_mipi_start=
_calibration(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->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 "failed to start MIPI calibration: %d\n", ret);
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 =
goto disable_mipi;
>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 }
>>>>> What would happen if CSI stream is enabled and then immediately
>>>>> disabled
>>>>> without enabling camera sensor?
>>>> Nothing will happen as during stream enable csi receiver is kept ready=
.
>>>>
>>>> But actual capture will not happen during that point.
>>> Could you please show how the full call chain looks like? It's not clea=
r
>>> to me what keeps CSI stream "ready".
>> VI is the main video input (video device) and on streaming it starts
>> stream of CSI subdev prior to stream of Sensor.
>>
>> HW path, sensor stream (CSI TX) -> CSI stream (RX)
>>
>> During CSI stream on, CSI PHY receiver is enabled to start receiving the
>> data but internally capture assembled to active state will happen only
>> when Tegra VI single shot is issues where VI thru pixel parser gets
>> captures data into the memory
> Alright, I see now.
>
> Will be great if you could change this hunk:
>
> {
>    ret =3D v4l2_subdev_call(src_subdev, video, s_stream, true);
>    if (ret < 0 && ret !=3D -ENOIOCTLCMD) {
>      tegra_mipi_cancel_calibration(csi_chan->mipi);
>      v4l2_subdev_call(csi_subdev, video, s_stream, false);
>      return ret;
>    }
> }
>
> to look like this:
>
> {
>    err =3D v4l2_subdev_call(src_subdev, video, s_stream, true);
>    if (err < 0 && err !=3D -ENOIOCTLCMD)
>      goto err_disable_csi_stream;
> ...
>    return 0;
>
> err_disable_csi_stream:
>    tegra_mipi_cancel_calibration(csi_chan->mipi);
>
>    v4l2_subdev_call(csi_subdev, video, s_stream, false);
>
>    return err;
> }
>
>
> It should make code a bit easier to read and follow.
>
> Otherwise this patch looks good to me, thanks.

Thanks Dmitry. Will send v7 now with this minor fix and would like to=20
close on this soon.

Sowjanya