On Wed, 21 Feb 2024 at 00:40, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > > > > On 2/19/2024 3:52 AM, Dmitry Baryshkov wrote: > > On Wed, 14 Feb 2024 at 22:36, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > >> > >> > >> > >> On 2/14/2024 11:20 AM, Dmitry Baryshkov wrote: > >>> On Wed, 14 Feb 2024 at 20:02, Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx> wrote: > >>>> > >>>> > >>>> > >>>> On 2/8/2024 6:50 AM, Dmitry Baryshkov wrote: > >>>>> We have several reports of vblank timeout messages. However after some > >>>>> debugging it was found that there might be different causes to that. > >>>>> To allow us to identify the DPU block that gets stuck, include the > >>>>> actual CTL_FLUSH value into the timeout message and trigger the devcore > >>>>> snapshot capture. > >>>>> > >>>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > >>>>> --- > >>>>> Changes in v2: > >>>>> - Added a call to msm_disp_snapshot_state() to trigger devcore dump > >>>>> (Abhinav) > >>>>> - Link to v1: https://lore.kernel.org/r/20240106-fd-dpu-debug-timeout-v1-1-6d9762884641@xxxxxxxxxx > >>>>> --- > >>>>> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 3 ++- > >>>>> 1 file changed, 2 insertions(+), 1 deletion(-) > >>>>> > >>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c > >>>>> index d0f56c5c4cce..a8d6165b3c0a 100644 > >>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c > >>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c > >>>>> @@ -489,7 +489,8 @@ static int dpu_encoder_phys_vid_wait_for_commit_done( > >>>>> (hw_ctl->ops.get_flush_register(hw_ctl) == 0), > >>>>> msecs_to_jiffies(50)); > >>>>> if (ret <= 0) { > >>>>> - DPU_ERROR("vblank timeout\n"); > >>>>> + DPU_ERROR("vblank timeout: %x\n", hw_ctl->ops.get_flush_register(hw_ctl)); > >>>>> + msm_disp_snapshot_state(phys_enc->parent->dev); > >>>> > >>>> > >>>> There is no rate limiting in this piece of code unfortunately. So this > >>>> will flood the number of snapshots. > >>> > >>> Well... Yes and no. The devcoredump will destroy other snapshots if > >>> there is a pending one. So only the console will be flooded and only > >>> in case when MSM_DISP_SNAPSHOT_DUMP_IN_CONSOLE is enabled. > >>> > >> > >> Yes, true but at the same time this makes it hard to capture a good dump > >> as potentially every vblank you could timeout so this destroy/create > >> cycle wont end. > > > > Excuse me, maybe I miss something. On the first timeout the snapshot > > is created. It is held by the kernel until it is fully read out from > > the userspace. Other snapshots will not interfere with this snapshot. > > > > For every new snapshot a new devcoredump device will be created which > should remain till it has been read. But now this will be created every > blank. IMO, this is really too much data for no reason. No-no-no. If there is a devcoredump for a device, the next one will not be created. See dev_coredumpm(). So all the snapshots will be created and then destroyed immediately. > > Subsequent vblank timeouts are not going to give any new information > compared to the existing snapshot of the first vblank timeout thats why > we should just create the snapshot when the first error happens and stop. > > For other frame done timeouts, infact subsequent timeouts without any > sort of recovery in between are quite misleading because hardware was > already not able to fetch the previous frame so it will most likely not > fetch the next one either till it has recovered. Typically thats why > these vblank timeouts happen in a flurry as the hardware never really > recovered from the first timeout. > > > Or are you worried that snapshotting takes time, so taking a snapshot > > will also interfere with the vblank timings for the next vblank? > > > > Yes this is another point. -- With best wishes Dmitry
