On 7/16/2024 2:50 PM, Rob Clark wrote:
On Tue, Jul 16, 2024 at 2:45 PM Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote:
On 7/15/2024 12:51 PM, Rob Clark wrote:
On Mon, Jul 1, 2024 at 12:43 PM Dmitry Baryshkov
<dmitry.baryshkov@xxxxxxxxxx> wrote:
On Fri, Jun 28, 2024 at 02:48:47PM GMT, Abhinav Kumar wrote:
There is no recovery mechanism in place yet to recover from mmu
faults for DPU. We can only prevent the faults by making sure there
is no misconfiguration.
Rate-limit the snapshot capture for mmu faults to once per
msm_kms_init_aspace() as that should be sufficient to capture
the snapshot for debugging otherwise there will be a lot of
dpu snapshots getting captured for the same fault which is
redundant and also might affect capturing even one snapshot
accurately.
Please squash this into the first patch. There is no need to add code
with a known defficiency.
Also, is there a reason why you haven't used <linux/ratelimit.h> ?
So, in some ways devcoredump is ratelimited by userspace needing to
clear an existing devcore..
Yes, a new devcoredump device will not be created until the previous one
is consumed or times out but here I am trying to limit even the DPU
snapshot capture because DPU register space is really huge and the rate
at which smmu faults occur is quite fast that its causing instability
while snapshots are being captured.
What I'd suggest would be more useful is to limit the devcores to once
per atomic update, ie. if display state hasn't changed, maybe an
additional devcore isn't useful
BR,
-R
By display state change, do you mean like the checks we have in
drm_atomic_crtc_needs_modeset()?
OR do you mean we need to cache the previous (currently picked up by hw)
state and trigger a new devcores if the new state is different by
comparing more things?
This will help to reduce the snapshots to unique frame updates but I do
not think it will reduce the rate enough for the case where DPU did not
recover from the previous fault.
I was thinking the easy thing, of just resetting the counter in
msm_atomic_commit_tail().. I suppose we could be clever filter out
updates that only change scanout address. Or hash the atomic state
and only generate devcoredumps for unique states. But I'm not sure
how over-complicated we should make this.
BR,
-R
Its a good idea actually and I would also like to keep it simple :)
One question, is it okay to assume that all compositors will only issue
unique commits? Because we are assuming thats the case with resetting
the counter in msm_atomic_commit_tail().
Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
---
drivers/gpu/drm/msm/msm_kms.c | 6 +++++-
drivers/gpu/drm/msm/msm_kms.h | 3 +++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/msm/msm_kms.c b/drivers/gpu/drm/msm/msm_kms.c
index d5d3117259cf..90a333920c01 100644
--- a/drivers/gpu/drm/msm/msm_kms.c
+++ b/drivers/gpu/drm/msm/msm_kms.c
@@ -168,7 +168,10 @@ static int msm_kms_fault_handler(void *arg, unsigned long iova, int flags, void
{
struct msm_kms *kms = arg;
- msm_disp_snapshot_state(kms->dev);
+ if (!kms->fault_snapshot_capture) {
+ msm_disp_snapshot_state(kms->dev);
+ kms->fault_snapshot_capture++;
When is it decremented?
+ }
return -ENOSYS;
}
@@ -208,6 +211,7 @@ struct msm_gem_address_space *msm_kms_init_aspace(struct drm_device *dev)
mmu->funcs->destroy(mmu);
}
+ kms->fault_snapshot_capture = 0;
msm_mmu_set_fault_handler(aspace->mmu, kms, msm_kms_fault_handler);
return aspace;
diff --git a/drivers/gpu/drm/msm/msm_kms.h b/drivers/gpu/drm/msm/msm_kms.h
index 1e0c54de3716..240b39e60828 100644
--- a/drivers/gpu/drm/msm/msm_kms.h
+++ b/drivers/gpu/drm/msm/msm_kms.h
@@ -134,6 +134,9 @@ struct msm_kms {
int irq;
bool irq_requested;
+ /* rate limit the snapshot capture to once per attach */
+ int fault_snapshot_capture;
+
/* mapper-id used to request GEM buffer mapped for scanout: */
struct msm_gem_address_space *aspace;
--
2.44.0
--
With best wishes
Dmitry
