Messages in this thread | | | Date | Wed, 13 Jul 2022 00:45:33 +0530 | Subject | Re: [Freedreno] [PATCH v2 3/7] drm/msm: Fix cx collapse issue during recovery | From | Akhil P Oommen <> |
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On 7/12/2022 10:14 PM, Rob Clark wrote: > On Mon, Jul 11, 2022 at 10:05 PM Akhil P Oommen > <quic_akhilpo@quicinc.com> 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@quicinc.com> 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@quicinc.com> >>>> --- >>>> >>>> (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?
-Akhil.
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