Messages in this thread | | | Date | Tue, 25 Jun 2019 14:40:12 -0700 | From | Jeykumar Sankaran <> | Subject | Re: drm/msm/dpu: Correct dpu encoder spinlock initialization |
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On 2019-06-24 22:44, dhar@codeaurora.org wrote: > On 2019-06-25 03:56, Jeykumar Sankaran wrote: >> On 2019-06-23 23:27, Shubhashree Dhar wrote: >>> dpu encoder spinlock should be initialized during dpu encoder >>> init instead of dpu encoder setup which is part of commit. >>> There are chances that vblank control uses the uninitialized >>> spinlock if not initialized during encoder init. >> Not much can be done if someone is performing a vblank operation >> before encoder_setup is done. >> Can you point to the path where this lock is acquired before >> the encoder_setup? >> >> Thanks >> Jeykumar S. >>> > > When running some dp usecase, we are hitting this callstack. > > Process kworker/u16:8 (pid: 215, stack limit = 0x00000000df9dd930) > Call trace: > spin_dump+0x84/0x8c > spin_dump+0x0/0x8c > do_raw_spin_lock+0x80/0xb0 > _raw_spin_lock_irqsave+0x34/0x44 > dpu_encoder_toggle_vblank_for_crtc+0x8c/0xe8 > dpu_crtc_vblank+0x168/0x1a0 > dpu_kms_enable_vblank+0[ 11.648998] vblank_ctrl_worker+0x3c/0x60 > process_one_work+0x16c/0x2d8 > worker_thread+0x1d8/0x2b0 > kthread+0x124/0x134 > > Looks like vblank is getting enabled earlier causing this issue and we > are using the spinlock without initializing it. > > Thanks, > Shubhashree > DP calls into set_encoder_mode during hotplug before even notifying the u/s. Can you trace out the original caller of this stack?
Even though the patch is harmless, I am not entirely convinced to move this initialization. Any call which acquires the lock before encoder_setup will be a no-op since there will not be any physical encoder to work with.
Thanks and Regards, Jeykumar S.
>>> Change-Id: I5a18b95fa47397c834a266b22abf33a517b03a4e >>> Signed-off-by: Shubhashree Dhar <dhar@codeaurora.org> >>> --- >>> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c >>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c >>> index 5f085b5..22938c7 100644 >>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c >>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c >>> @@ -2195,8 +2195,6 @@ int dpu_encoder_setup(struct drm_device *dev, >>> struct >>> drm_encoder *enc, >>> if (ret) >>> goto fail; >>> >>> - spin_lock_init(&dpu_enc->enc_spinlock); >>> - >>> atomic_set(&dpu_enc->frame_done_timeout, 0); >>> timer_setup(&dpu_enc->frame_done_timer, >>> dpu_encoder_frame_done_timeout, 0); >>> @@ -2250,6 +2248,7 @@ struct drm_encoder *dpu_encoder_init(struct >>> drm_device *dev, >>> >>> drm_encoder_helper_add(&dpu_enc->base, &dpu_encoder_helper_funcs); >>> >>> + spin_lock_init(&dpu_enc->enc_spinlock); >>> dpu_enc->enabled = false; >>> >>> return &dpu_enc->base;
-- Jeykumar S
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