[RFC PATCH] drm/msm/dpu: Move TE setup to prepare_for_kickoff()

[Dmitry Baryshkov]

On 09/02/2023 01:24, Jessica Zhang wrote:
> 
> 
> On 2/8/2023 2:18 PM, Dmitry Baryshkov wrote:
>> On 08/02/2023 23:37, Jessica Zhang wrote:
>>> Currently, DPU will enable TE during prepare_commit(). However, this
>>> will cause issues when trying to read/write to register in
>>> get_autorefresh_config(), because the core clock rates aren't set at
>>> that time.
>>>
>>> This used to work because phys_enc->hw_pp is only initialized in mode
>>> set [1], so the first prepare_commit() will return before any register
>>> read/write as hw_pp would be NULL.
>>>
>>> However, when we try to implement support for INTF TE, we will run into
>>> the clock issue described above as hw_intf will *not* be NULL on the
>>> first prepare_commit(). This is because the initialization of
>>> dpu_enc->hw_intf has been moved to dpu_encoder_setup() [2].
>>>
>>> To avoid this issue, let's enable TE during prepare_for_kickoff()
>>> instead as the core clock rates are guaranteed to be set then.
>>>
>>> Depends on: "Implement tearcheck support on INTF block" [3]
>>>
>>> [1] 
>>> https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c#L1109
>>> [2] 
>>> https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c#L2339
>>> [3] https://patchwork.freedesktop.org/series/112332/
>>>
>>> Signed-off-by: Jessica Zhang <quic_jesszhan at quicinc.com>
>>> ---
>>>   .../drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c  | 78 ++++++++++---------
>>>   1 file changed, 43 insertions(+), 35 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c 
>>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
>>> index 279a0b7015ce..746250bce3d1 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
>>> @@ -587,39 +587,6 @@ static void dpu_encoder_phys_cmd_destroy(struct 
>>> dpu_encoder_phys *phys_enc)
>>>       kfree(cmd_enc);
>>>   }
>>> -static void dpu_encoder_phys_cmd_prepare_for_kickoff(
>>> -        struct dpu_encoder_phys *phys_enc)
>>> -{
>>> -    struct dpu_encoder_phys_cmd *cmd_enc =
>>> -            to_dpu_encoder_phys_cmd(phys_enc);
>>> -    int ret;
>>> -
>>> -    if (!phys_enc->hw_pp) {
>>> -        DPU_ERROR("invalid encoder\n");
>>> -        return;
>>> -    }
>>> -    DRM_DEBUG_KMS("id:%u pp:%d pending_cnt:%d\n", 
>>> DRMID(phys_enc->parent),
>>> -              phys_enc->hw_pp->idx - PINGPONG_0,
>>> -              atomic_read(&phys_enc->pending_kickoff_cnt));
>>> -
>>> -    /*
>>> -     * Mark kickoff request as outstanding. If there are more than one,
>>> -     * outstanding, then we have to wait for the previous one to 
>>> complete
>>> -     */
>>> -    ret = _dpu_encoder_phys_cmd_wait_for_idle(phys_enc);
>>> -    if (ret) {
>>> -        /* force pending_kickoff_cnt 0 to discard failed kickoff */
>>> -        atomic_set(&phys_enc->pending_kickoff_cnt, 0);
>>> -        DRM_ERROR("failed wait_for_idle: id:%u ret:%d pp:%d\n",
>>> -              DRMID(phys_enc->parent), ret,
>>> -              phys_enc->hw_pp->idx - PINGPONG_0);
>>> -    }
>>> -
>>> -    DPU_DEBUG_CMDENC(cmd_enc, "pp:%d pending_cnt %d\n",
>>> -            phys_enc->hw_pp->idx - PINGPONG_0,
>>> -            atomic_read(&phys_enc->pending_kickoff_cnt));
>>> -}
>>> -
>>>   static bool dpu_encoder_phys_cmd_is_ongoing_pptx(
>>>           struct dpu_encoder_phys *phys_enc)
>>>   {
>>> @@ -645,8 +612,7 @@ static bool dpu_encoder_phys_cmd_is_ongoing_pptx(
>>>       return false;
>>>   }
>>> -static void dpu_encoder_phys_cmd_prepare_commit(
>>> -        struct dpu_encoder_phys *phys_enc)
>>> +static void dpu_encoder_phys_cmd_enable_te(struct dpu_encoder_phys 
>>> *phys_enc)
>>>   {
>>>       struct dpu_encoder_phys_cmd *cmd_enc =
>>>           to_dpu_encoder_phys_cmd(phys_enc);
>>> @@ -704,6 +670,48 @@ static void dpu_encoder_phys_cmd_prepare_commit(
>>>                "disabled autorefresh\n");
>>>   }
>>> +static void dpu_encoder_phys_cmd_prepare_for_kickoff(
>>> +        struct dpu_encoder_phys *phys_enc)
>>
>> Could you please move the function back to the place, so that we can 
>> see the actual difference?
> 
> Hi Dmitry,
> 
> This function was moved because prepare_commit() and is_ongoing_pptx() 
> (which is called in prepare_commit()) were originally defined later in 
> the file.
> 
>>
>>> +{
>>> +    struct dpu_encoder_phys_cmd *cmd_enc =
>>> +            to_dpu_encoder_phys_cmd(phys_enc);
>>> +    int ret;
>>> +
>>> +    if (!phys_enc->hw_pp) {
>>> +        DPU_ERROR("invalid encoder\n");
>>> +        return;
>>> +    }
>>> +
>>> +
>>> +    DRM_DEBUG_KMS("id:%u pp:%d pending_cnt:%d\n", 
>>> DRMID(phys_enc->parent),
>>> +              phys_enc->hw_pp->idx - PINGPONG_0,
>>> +              atomic_read(&phys_enc->pending_kickoff_cnt));
>>> +
>>> +    /*
>>> +     * Mark kickoff request as outstanding. If there are more than one,
>>> +     * outstanding, then we have to wait for the previous one to 
>>> complete
>>> +     */
>>> +    ret = _dpu_encoder_phys_cmd_wait_for_idle(phys_enc);
>>> +    if (ret) {
>>> +        /* force pending_kickoff_cnt 0 to discard failed kickoff */
>>> +        atomic_set(&phys_enc->pending_kickoff_cnt, 0);
>>> +        DRM_ERROR("failed wait_for_idle: id:%u ret:%d pp:%d\n",
>>> +              DRMID(phys_enc->parent), ret,
>>> +              phys_enc->hw_pp->idx - PINGPONG_0);
>>> +    }
>>> +
>>> +    dpu_encoder_phys_cmd_enable_te(phys_enc);
>>> +
>>> +    DPU_DEBUG_CMDENC(cmd_enc, "pp:%d pending_cnt %d\n",
>>> +            phys_enc->hw_pp->idx - PINGPONG_0,
>>> +            atomic_read(&phys_enc->pending_kickoff_cnt));
>>> +}
>>> +
>>> +static void dpu_encoder_phys_cmd_prepare_commit(
>>> +        struct dpu_encoder_phys *phys_enc)
>>> +{
>>> +}
>>
>> There is no need to have the empty callback, you can skip it 
>> completely. Actually, if it is not needed anymore for the cmd 
>> encoders, you can drop the .prepare_commit from struct 
>> dpu_encoder_phys_ops. And then, by extension, 
>> dpu_encoder_prepare_commit(), dpu_kms_prepare_commit(). This sounds 
>> like a nice second patch for this rfc.
> 
> Got it.
> 
> FWIW I kept this as an empty method to match mdp4_prepare_commit() [1], 
> but I can just add a NULL check in msm_atomic_commit_tail() and remove 
> both instances of empty callbacks if that's preferable.

yes, please.

> 
> [1] 
> https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c#L87


-- 
With best wishes
Dmitry