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SubjectRe: drm/msm/dpu: Correct dpu encoder spinlock initialization
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@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;


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