Re: [RFC PATCH v5 13/14] media: tegra-video: Add CSI MIPI pads calibration

From: Sowjanya Komatineni
Date: Tue Jul 28 2020 - 11:53:33 EST

On 7/28/20 3:30 AM, Dmitry Osipenko wrote:
27.07.2020 23:57, Sowjanya Komatineni ÐÐÑÐÑ:
+ /*
+ * TRM has incorrectly documented to wait for done status from
+ * calibration logic after CSI interface power on.
+ * As per the design, calibration results are latched and applied
+ * to the pads only when the link is in LP11 state which will happen
+ * during the sensor stream-on.
+ * CSI subdev stream-on triggers start of MIPI pads calibration.
+ * Wait for calibration to finish here after sensor subdev stream-on
+ * and in case of sensor stream-on failure, cancel the calibration.
+ */
subdev = on ? src_subdev : csi_subdev;
ret = v4l2_subdev_call(subdev, video, s_stream, on);
- if (ret < 0 && ret != -ENOIOCTLCMD)
+ if (ret < 0 && ret != -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

+ if (on && csi_chan->mipi)
+ tegra_mipi_cancel_calibration(csi_chan->mipi);
return ret;
+ }
+ if (on && csi_chan->mipi) {
Does finish_calibration() really need to be called for ret=-ENOIOCTLCMD?

Shouldn't it be cancel_calibration( for the -ENOIOCTLCMD?

start calibration happens during csi sensor streaming which happens prior to this point.

In case if sensor subdev does not have s_stream ops, then either finish/cancel calibration should happen to disable the clock.

+ ret = tegra_mipi_finish_calibration(csi_chan->mipi);
+ if (ret < 0)
+ dev_err(csi_chan->csi->dev,
+ "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 power anyway.

Also we only did csi subdev s_stream on and during sensor subdev s_stream on fail, actual stream dont happen and on tegra side frame capture by HW happens only when kthreads run.
+ return ret;
+ }
return 0;