linux-kernel - Re: [PATCH v7 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and get crtc from connector state instead of dpu

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Date:   Tue, 13 Sep 2022 20:05:35 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Vinod Polimera <quic_vpolimer@...cinc.com>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, robdclark@...il.com,
        dianders@...omium.org, swboyd@...omium.org,
        quic_kalyant@...cinc.com, quic_khsieh@...cinc.com,
        quic_vproddut@...cinc.com, quic_bjorande@...cinc.com,
        quic_aravindh@...cinc.com, quic_abhinavk@...cinc.com,
        quic_sbillaka@...cinc.com
Subject: Re: [PATCH v7 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and get
 crtc from connector state instead of dpu_enc

On 13/09/2022 20:04, Dmitry Baryshkov wrote:
> On 13/09/2022 17:51, Vinod Polimera wrote:
>> Update crtc retrieval from dpu_enc to dpu_enc connector state,
>> since new links get set as part of the dpu enc virt mode set.
>> The dpu_enc->crtc cache is no more needed, hence cleaning it as
>> part of this change.
>>
>> Signed-off-by: Vinod Polimera <quic_vpolimer@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c    |  4 ----
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 35 
>> ++++++++++++-----------------
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h |  8 -------
>>   3 files changed, 14 insertions(+), 33 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> index 13ce321..8ec9a13 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> @@ -1029,7 +1029,6 @@ static void dpu_crtc_disable(struct drm_crtc *crtc,
>>            */
>>           if (dpu_encoder_get_intf_mode(encoder) == INTF_MODE_VIDEO)
>>               release_bandwidth = true;
>> -        dpu_encoder_assign_crtc(encoder, NULL);
>>       }
>>       /* wait for frame_event_done completion */
>> @@ -1099,9 +1098,6 @@ static void dpu_crtc_enable(struct drm_crtc *crtc,
>>       trace_dpu_crtc_enable(DRMID(crtc), true, dpu_crtc);
>>       dpu_crtc->enabled = true;
>> -    drm_for_each_encoder_mask(encoder, crtc->dev, 
>> crtc->state->encoder_mask)
>> -        dpu_encoder_assign_crtc(encoder, crtc);
>> -
>>       /* Enable/restore vblank irq handling */
>>       drm_crtc_vblank_on(crtc);
>>   }
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 9c6817b..0c7d8b5 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -132,11 +132,6 @@ enum dpu_enc_rc_states {
>>    * @intfs_swapped:    Whether or not the phys_enc interfaces have 
>> been swapped
>>    *            for partial update right-only cases, such as pingpong
>>    *            split where virtual pingpong does not generate IRQs
>> - * @crtc:        Pointer to the currently assigned crtc. Normally you
>> - *            would use crtc->state->encoder_mask to determine the
>> - *            link between encoder/crtc. However in this case we need
>> - *            to track crtc in the disable() hook which is called
>> - *            _after_ encoder_mask is cleared.
>>    * @connector:        If a mode is set, cached pointer to the active 
>> connector
>>    * @crtc_kickoff_cb:        Callback into CRTC that will flush & start
>>    *                all CTL paths
>> @@ -181,7 +176,6 @@ struct dpu_encoder_virt {
>>       bool intfs_swapped;
>> -    struct drm_crtc *crtc;
>>       struct drm_connector *connector;
>>       struct dentry *debugfs_root;
>> @@ -1288,6 +1282,7 @@ static void dpu_encoder_vblank_callback(struct 
>> drm_encoder *drm_enc,
>>           struct dpu_encoder_phys *phy_enc)
>>   {
>>       struct dpu_encoder_virt *dpu_enc = NULL;
>> +    struct drm_crtc *crtc;
>>       unsigned long lock_flags;
>>       if (!drm_enc || !phy_enc)
>> @@ -1298,9 +1293,14 @@ static void dpu_encoder_vblank_callback(struct 
>> drm_encoder *drm_enc,
>>       atomic_inc(&phy_enc->vsync_cnt);
>> +    if (!dpu_enc->connector || !dpu_enc->connector->state)
>> +        return;
>> +
>> +    crtc = dpu_enc->connector->state->crtc;
>> +
>>       spin_lock_irqsave(&dpu_enc->enc_spinlock, lock_flags);
>> -    if (dpu_enc->crtc)
>> -        dpu_crtc_vblank_callback(dpu_enc->crtc);
>> +    if (crtc)
>> +        dpu_crtc_vblank_callback(crtc);
>>       spin_unlock_irqrestore(&dpu_enc->enc_spinlock, lock_flags);
> 
> Stephen's comment about reading the state from outside of the lock and 
> then using local variable under spinlock is still valid. Moreover I'm 
> not sure that enc_spinlock protects connector's state. I'd say one has 
> to take the modesetting lock here.

s/Stephen's/Doug's/

-- 
With best wishes
Dmitry