On 7/20/2022 11:36 PM, Rob Clark wrote:
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
Yes, you are right. There could be some transient votes from other
threads/drivers/subsystem. This is the reason we need to poll for cx
gdsc collapse in the next patch.Even with #1, it is difficult to
coordinate with smmu driver and close to impossible with tz/hyp.
-Akhil.
