Re: [RFC PATCH v6 09/10] media: tegra-video: Add CSI MIPI pads calibration

[Sowjanya Komatineni]

On 7/31/20 1:42 PM, Dmitry Osipenko wrote:
> 31.07.2020 19:29, Sowjanya Komatineni ÐÐÑÐÑ:
> > On 7/31/20 9:14 AM, Dmitry Osipenko wrote:
> > > 31.07.2020 18:46, Sowjanya Komatineni ÐÐÑÐÑ:
> > > > On 7/31/20 4:39 AM, Dmitry Osipenko wrote:
> > > > > 31.07.2020 12:02, Sowjanya Komatineni ÐÐÑÐÑ:
> > > > > ...
> > > > > > @@ -249,13 +249,47 @@ static int tegra_csi_enable_stream(struct
> > > > > > v4l2_subdev *subdev)
> > > > > >  ÂÂÂÂÂÂÂÂÂÂ return ret;
> > > > > >  ÂÂÂÂÂÂ }
> > > > > >  ÂÂ +ÂÂÂ if (csi_chan->mipi) {
> > > > > > +ÂÂÂÂÂÂÂ ret = tegra_mipi_enable(csi_chan->mipi);
> > > > > > +ÂÂÂÂÂÂÂ if (ret < 0) {
> > > > > > +ÂÂÂÂÂÂÂÂÂÂÂ dev_err(csi->dev,
> > > > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ "failed to enable MIPI pads: %d\n", ret);
> > > > > > +ÂÂÂÂÂÂÂÂÂÂÂ goto rpm_put;
> > > > > > +ÂÂÂÂÂÂÂ }
> > > > > > +
> > > > > > +ÂÂÂÂÂÂÂ /*
> > > > > > +ÂÂÂÂÂÂÂÂ * CSI MIPI pads PULLUP, PULLDN and TERM impedances need to
> > > > > > +ÂÂÂÂÂÂÂÂ * be calibrated after power on.
> > > > > > +ÂÂÂÂÂÂÂÂ * So, trigger the calibration start here and results will
> > > > > > +ÂÂÂÂÂÂÂÂ * be latched and applied to the pads when link is in LP11
> > > > > > +ÂÂÂÂÂÂÂÂ * state during start of sensor streaming.
> > > > > > +ÂÂÂÂÂÂÂÂ */
> > > > > > +ÂÂÂÂÂÂÂ ret = tegra_mipi_start_calibration(csi_chan->mipi);
> > > > > > +ÂÂÂÂÂÂÂ if (ret < 0) {
> > > > > > +ÂÂÂÂÂÂÂÂÂÂÂ dev_err(csi->dev,
> > > > > > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ "failed to start MIPI calibration: %d\n", ret);
> > > > > > +ÂÂÂÂÂÂÂÂÂÂÂ goto disable_mipi;
> > > > > > +ÂÂÂÂÂÂÂ }
> > > > > 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 clear
> > > 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 = v4l2_subdev_call(src_subdev, video, s_stream, true);
>    if (ret < 0 && ret != -ENOIOCTLCMD) {
>      tegra_mipi_cancel_calibration(csi_chan->mipi);
>      v4l2_subdev_call(csi_subdev, video, s_stream, false);
>      return ret;
>    }
> }
>
> to look like this:
>
> {
>    err = v4l2_subdev_call(src_subdev, video, s_stream, true);
>    if (err < 0 && err != -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 
close on this soon.

Sowjanya