On 10/05/2022 16:33, Kieran Bingham wrote:
Hi Terry,
Quoting Terry Barnaby (2022-05-10 14:35:38)
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().
I don't think I can see this file in the latest linux sources. Are you
working on an out of tree BSP driver supported by a vendor?
If so - you might be able to contact them directly for support, but if
we don't have the source code it can be hard to support your issue.
--
Regards
Kieran
Sorry, top posted in previous email (all different groups methods). I
have repeated my response here.
Hi Kiera,
Thanks for you response. Yes its from the NXP Yocto distribution with
kernel at: git://source.codeaurora.org/external/imx/linux-imx.git
But I wasn't after specific information/help with this platform, I was
really trying to find out if there is a mechanism within the
mainline/standard Video4Linux kernel API's such that a video front end
subdev can get some function called once the video pipeline has been
setup ie. All hardware modules configured and ready to run a video stream.
For example there is the s_stream() function pointer in
v4l2_subdev_video_ops, but that function is called before the later (in
pipeline) CSI2 module is started and I need a function to be called
after all of the pipelines hardware has been initialised to get around
this hardware feature/issue.
Terry
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
