Re: [PATCH] media: amd: isp4: add system suspend/resume support

[Kinn Coelho Juliao]

Thanks Pratap, Mario.

I reviewed commit 0288a345f19b ("drm/amdgpu/isp: fix SMU warning
during ISP suspend-resume"). I understand it marks ISP MFD children as
syscore devices and manages their suspend/resume from the amdgpu parent
via pm_runtime_force_suspend/resume.

I'm curious about one thing though; on my current system (7.0-rc1),
s2idle resume still hangs with the in-tree V4L2 module loaded. My
out-of-tree module, which adds dev_pm_ops that call
isp4sd_pwroff_and_deinit() before suspend, resolves the hang.

pm_runtime_force_suspend() manages the power domain but doesn't tear
down firmware ring buffers or V4L2 streaming state. If the camera was
active at any point during the session when suspend occurs, the driver
would have stale state on resume. That seems to be what's causing the
hang on my hardware (HP ZBook Ultra G1a, Strix Halo).

Is the firmware/streaming state teardown handled elsewhere that I'm
missing, or does the V4L2 driver still need its own suspend path?

Thanks,
Kinn