On 2020-05-14 21:47, Doug Anderson wrote:
Hi,
On Fri, May 1, 2020 at 6:31 AM Kalyan Thota <kalya...@codeaurora.org>
wrote:
"The PM core always increments the runtime usage counter
before calling the ->suspend() callback and decrements it
after calling the ->resume() callback"
DPU and DSI are managed as runtime devices. When
suspend is triggered, PM core adds a refcount on all the
devices and calls device suspend, since usage count is
already incremented, runtime suspend was not getting called
and it kept the clocks on which resulted in target not
entering into XO shutdown.
Add changes to force suspend on runtime devices during pm sleep.
Changes in v1:
- Remove unnecessary checks in the function
_dpu_kms_disable_dpu (Rob Clark).
Changes in v2:
- Avoid using suspend_late to reset the usagecount
as suspend_late might not be called during suspend
call failures (Doug).
Changes in v3:
- Use force suspend instead of managing device usage_count
via runtime put and get API's to trigger callbacks (Doug).
Changes in v4:
- Check the return values of pm_runtime_force_suspend and
pm_runtime_force_resume API's and pass appropriately (Doug).
Changes in v5:
Can you please put the version number properly in your subject? It's
really hard to tell one version of your patch from another.
- With v4 patch, test cycle has uncovered issues in device resume.
On bubs: cmd tx failures were seen as SW is sending panel off
commands when the dsi resources are turned off.
Upon suspend, DRM driver will issue a NULL composition to the
dpu, followed by turning off all the HW blocks.
v5 changes will serialize the NULL commit and resource unwinding
by handling them under PM prepare and PM complete phases there by
ensuring that clks are on when panel off commands are being
processed.
I'm still most definitely not an expert in how all the DRM pieces all
hook up together, but the solution you have in this patch seems wrong
to me. As far as I can tell the "prepare" state isn't supposed to be
actually doing the suspend work and here that's exactly what you're
doing. I think you should find a different solution to ensure
ordering is correct.
-Doug
Hi,
Prepare and Complete are callbacks defined as part of Sleep and Resume
sequence
Entering PM SUSPEND the phases are : prepare --> suspend -->
suspend_late --> suspend_noirq.
While leaving PM SUSPEND the phases are: resume_noirq --> resume_early
--> resume --> complete.
The reason to push drm suspend handling to PM prepare phase is that
parent here will trigger a modeset to turn off the timing and
subsequently the panel.
the child devices should not turn of their clocks before parent unwinds
the composition. Hence they are serialized as per the sequence mentioned
above.
A similar approach is taken by other driver that use drm framework. In
this driver, the device registers for prepare and complete callbacks to
handle drm_suspend and drm_resume.
https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/exynos/exynos_drm_drv.c#L163
Kalyan
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