On Tue, Jul 12, 2022 at 12:15 PM Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> wrote: > > On 7/12/2022 10:14 PM, Rob Clark wrote: > > On Mon, Jul 11, 2022 at 10:05 PM Akhil P Oommen > > <quic_akhilpo@xxxxxxxxxxx> wrote: > >> On 7/12/2022 4:52 AM, Doug Anderson wrote: > >>> Hi, > >>> > >>> On Fri, Jul 8, 2022 at 11:00 PM Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> wrote: > >>>> There are some hardware logic under CX domain. For a successful > >>>> recovery, we should ensure cx headswitch collapses to ensure all the > >>>> stale states are cleard out. This is especially true to for a6xx family > >>>> where we can GMU co-processor. > >>>> > >>>> Currently, cx doesn't collapse due to a devlink between gpu and its > >>>> smmu. So the *struct gpu device* needs to be runtime suspended to ensure > >>>> that the iommu driver removes its vote on cx gdsc. > >>>> > >>>> Signed-off-by: Akhil P Oommen <quic_akhilpo@xxxxxxxxxxx> > >>>> --- > >>>> > >>>> (no changes since v1) > >>>> > >>>> drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 16 ++++++++++++++-- > >>>> drivers/gpu/drm/msm/msm_gpu.c | 2 -- > >>>> 2 files changed, 14 insertions(+), 4 deletions(-) > >>>> > >>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >>>> index 4d50110..7ed347c 100644 > >>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c > >>>> @@ -1278,8 +1278,20 @@ static void a6xx_recover(struct msm_gpu *gpu) > >>>> */ > >>>> gmu_write(&a6xx_gpu->gmu, REG_A6XX_GMU_GMU_PWR_COL_KEEPALIVE, 0); > >>>> > >>>> - gpu->funcs->pm_suspend(gpu); > >>>> - gpu->funcs->pm_resume(gpu); > >>>> + /* > >>>> + * Now drop all the pm_runtime usage count to allow cx gdsc to collapse. > >>>> + * First drop the usage count from all active submits > >>>> + */ > >>>> + for (i = gpu->active_submits; i > 0; i--) > >>>> + pm_runtime_put(&gpu->pdev->dev); > >>>> + > >>>> + /* And the final one from recover worker */ > >>>> + pm_runtime_put_sync(&gpu->pdev->dev); > >>>> + > >>>> + for (i = gpu->active_submits; i > 0; i--) > >>>> + pm_runtime_get(&gpu->pdev->dev); > >>>> + > >>>> + pm_runtime_get_sync(&gpu->pdev->dev); > >>> In response to v1, Rob suggested pm_runtime_force_suspend/resume(). > >>> Those seem like they would work to me, too. Why not use them? > >> Quoting my previous response which I seem to have sent only to Freedreno > >> list: > >> > >> "I believe it is supposed to be used only during system sleep state > >> transitions. Btw, we don't want pm_runtime_get() calls from elsewhere to > >> fail by disabling RPM here." > > The comment about not wanting other runpm calls to fail is valid.. but > > that is also solveable, ie. by holding a lock around runpm calls. > > Which I think we need to do anyways, otherwise looping over > > gpu->active_submits is racey.. > > > > I think pm_runtime_force_suspend/resume() is the least-bad option.. or > > at least I'm not seeing any obvious alternative that is better > > > > BR, > > -R > We are holding gpu->lock here which will block further submissions from > scheduler. Will active_submits still race? > > It is possible that there is another thread which successfully completed > pm_runtime_get() and while it access the hardware, we pulled the plug on > regulator/clock here. That will result in obvious device crash. So I can > think of 2 solutions: > > 1. wrap *every* pm_runtime_get/put with a mutex. Something like: > mutex_lock(); > pm_runtime_get(); > < ... access hardware here >> > pm_runtime_put(); > mutex_unlock(); > > 2. Drop runtime votes from every submit in recover worker and wait/poll > for regulator to collapse in case there are transient votes on > regulator from other threads/subsystems. > > Option (2) seems simpler to me. What do you think? > But I think without #1 you could still be racing w/ some other path that touches the hw, like devfreq, right. They could be holding a runpm ref, so even if you loop over active_submits decrementing the runpm ref, it still doesn't drop to zero BR, -R
