Re: drm/msm/dpu: Correct dpu encoder spinlock initialization

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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

Change-Id: I5a18b95fa47397c834a266b22abf33a517b03a4e
Signed-off-by: Shubhashree Dhar <dhar@xxxxxxxxxxxxxx>
---
 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;





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