Re: [PATCH] drm/msm/dpu: ensure device suspend happens during PM sleep

Hi,

On Wed, Mar 25, 2020 at 8:40 AM Rob Clark [off-list ref] wrote:

On Tue, Mar 24, 2020 at 7:35 AM Doug Anderson [off-list ref] wrote:

quoted

Hi,

On Sun, Mar 22, 2020 at 11:14 PM Kalyan Thota [off-list ref] wrote:

quoted

"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 manage runtime devices during pm sleep.

Changes in v1:
 - Remove unnecessary checks in the function
     _dpu_kms_disable_dpu (Rob Clark).

I'm wondering what happened with my feedback on v1, AKA:

https://lore.kernel.org/r/CAD=FV=VxzEV40g+ieuEN+7o=34+wM8MHO8o7T5zA1Yosx7SVWg@mail.gmail.com (local)

Maybe you didn't see it?  ...or if you or Rob think I'm way off base
(always possible) then please tell me so.

At least w/ the current patch, disable_dpu should not be called for
screen-off (although I'd hope if all the screens are off the device
would suspend).

OK, that's good.

But I won't claim to be a pm expert.. so not really
sure if this is the best approach or not.  I don't think our
arrangement of sub-devices under a parent is completely abnormal, so
it does feel like there should be a simpler solution..

I think the other arguments about asymmetry are still valid and I've
fixed bugs around this type of thing in the past.  For instance, see
commit f7ccbed656f7 ("drm/rockchip: Suspend DP late").


-Doug