Hi,
We are working on a system that uses a NXP IMX8MP SOC with a TP2855
analogue video front end chip that can capture 1920x1080p25 or PAL
720x576i25 analogue video streams which is generally working using
gstreamer as the higher level software driving this.
We have an intermittent video stream start up problem which we believe
is down to:
1. The TP2855 is initialised first and its subdev *_s_stream() call is
called to start the video input.
2. The NXP CSI2 video input hardware is then started:
imx8-mipi-csi2-sam.c: mipi_csis_s_stream().
3. The TP2855 enables the CSI2 clock after its *_s_stream() call,
probably in hardware after its PLL's have locked, by sending a CSI2
start sequence on the CSI2 clock pair. This clock is then a continuous
clock ie. it does not go into low power mode during horizontal/vertical
blanking.
4. The NXP CSI2 video input hardware, based on some Samsung IP, does not
see the CSI2 clock unless it sees the CSI2 start sequence and depending
on timings it may not see this at video pipeline startup and we get not
video stream from the CSI2 hardware.
I was hoping the subdev *_s_stream() call would be after all of the
hardware's pipeline was setup so I could instigate a CSI2 clock restart
in the TP2855 driver, but unfortunately this is called before the CSI2
hardware is setup.
I can add a one shot timer to do this in the TP2855 subdev *_s_stream()
call, but obviously this is not ideal. Is there anyway to get a subdev
function called in the video4linux API automatically once all of the
video streams hardware is setup ?
Any ideas/recommendations ?
Terry
