On 2019-06-26 03:10, Jeykumar Sankaran wrote:
On 2019-06-24 22:44, dhar@xxxxxxxxxxxxxx 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@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;
In dpu_crtc_vblank(), we are looping through all the encoders in the
present mode_config:
https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c#L1082
and hence calling dpu_encoder_toggle_vblank_for_crtc() for all the
encoders. But in dpu_encoder_toggle_vblank_for_crtc(), after acquiring
the spinlock, we will do a early return for
the encoders which are not currently assigned to our crtc:
https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c#L1318.
Since the encoder_setup for the secondary encoder(dp encoder in this
case) is not called until dp hotplug, we are hitting kernel panic while
acquiring the lock.
