Re: [PATCH 6/6] drm/msm/dpu: don't set crtc_state->mode_changed from atomic_check()

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

On 1/8/2025 6:27 PM, Abhinav Kumar wrote:
> 
> 
> On 12/21/2024 9:00 PM, Dmitry Baryshkov wrote:
>> The MSM driver uses drm_atomic_helper_check() which mandates that none
>> of the atomic_check() callbacks toggles crtc_state->mode_changed.
>> Perform corresponding check before calling the drm_atomic_helper_check()
>> function.
>>
>> Fixes: 8b45a26f2ba9 ("drm/msm/dpu: reserve cdm blocks for writeback in 
>> case of YUV output")
>> Reported-by: Simona Vetter <simona.vetter@ffwll.ch>
>> Closes: 
>> https://lore.kernel.org/dri-devel/ZtW_S0j5AEr4g0QW@phenom.ffwll.local/
>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 32 
>> +++++++++++++++++++++++++----
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h |  4 ++++
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c     | 26 
>> +++++++++++++++++++++++
>>   drivers/gpu/drm/msm/msm_atomic.c            | 13 +++++++++++-
>>   drivers/gpu/drm/msm/msm_kms.h               |  7 +++++++
>>   5 files changed, 77 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> index 
>> 209e6fb605b2d8724935b62001032e7d39540366..b7c3aa8d0e2ca58091deacdeaccb0819d2bf045c 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> @@ -753,6 +753,34 @@ static void 
>> dpu_encoder_assign_crtc_resources(struct dpu_kms *dpu_kms,
>>       cstate->num_mixers = num_lm;
>>   }
>> +/**
>> + * dpu_encoder_virt_check_mode_changed: check if full modeset is 
>> required
>> + * @drm_enc:    Pointer to drm encoder structure
>> + * @crtc_state:    Corresponding CRTC state to be checked
>> + * @conn_state: Corresponding Connector's state to be checked
>> + *
>> + * Check if the changes in the object properties demand full mode set.
>> + */
>> +int dpu_encoder_virt_check_mode_changed(struct drm_encoder *drm_enc,
>> +                    struct drm_crtc_state *crtc_state,
>> +                    struct drm_connector_state *conn_state)
>> +{
>> +    struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
>> +    struct msm_display_topology topology;
>> +
>> +    DPU_DEBUG_ENC(dpu_enc, "\n");
>> +
>> +    /* Using mode instead of adjusted_mode as it wasn't computed yet */
>> +    topology = dpu_encoder_get_topology(dpu_enc, &crtc_state->mode, 
>> crtc_state, conn_state);
>> +
>> +    if (topology.needs_cdm && !dpu_enc->cur_master->hw_cdm)
>> +        crtc_state->mode_changed = true;
>> +    else if (!topology.needs_cdm && dpu_enc->cur_master->hw_cdm)
>> +        crtc_state->mode_changed = true;
>> +
>> +    return 0;
>> +}
> 
> How will this work exactly?
> 
> needs_cdm is set in the encoder's atomic_check which is called inside 
> drm_atomic_helper_check(). But this function is called before that.
> 
> So needs_cdm will never hit.
>

Sorry, my bad. after change (4) of this series needs_cdm is also 
populated within  dpu_encoder_get_topology().

To follow up on 
https://patchwork.freedesktop.org/patch/629231/?series=137975&rev=4#comment_1148651

So is the plan for CWB to add a dpu_crtc_check_mode_changed() like 
dpu_encoder's and call it?


> 
>> +
>>   static int dpu_encoder_virt_atomic_check(
>>           struct drm_encoder *drm_enc,
>>           struct drm_crtc_state *crtc_state,
>> @@ -786,10 +814,6 @@ static int dpu_encoder_virt_atomic_check(
>>       topology = dpu_encoder_get_topology(dpu_enc, adj_mode, 
>> crtc_state, conn_state);
>> -    if (topology.needs_cdm && !dpu_enc->cur_master->hw_cdm)
>> -        crtc_state->mode_changed = true;
>> -    else if (!topology.needs_cdm && dpu_enc->cur_master->hw_cdm)
>> -        crtc_state->mode_changed = true;
>>       /*
>>        * Release and Allocate resources on every modeset
>>        */
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> index 
>> 92b5ee390788d16e85e195a664417896a2bf1cae..da133ee4701a329f566f6f9a7255f2f6d050f891 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>> @@ -88,4 +88,8 @@ void dpu_encoder_cleanup_wb_job(struct drm_encoder 
>> *drm_enc,
>>   bool dpu_encoder_is_valid_for_commit(struct drm_encoder *drm_enc);
>> +int dpu_encoder_virt_check_mode_changed(struct drm_encoder *drm_enc,
>> +                    struct drm_crtc_state *crtc_state,
>> +                    struct drm_connector_state *conn_state);
>> +
>>   #endif /* __DPU_ENCODER_H__ */
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c 
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> index 
>> dae8a94d3366abfb8937d5f44d8968f1d0691c2d..e2d822f7d785dc0debcb28595029a3e2050b0cf4 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>> @@ -446,6 +446,31 @@ static void dpu_kms_disable_commit(struct msm_kms 
>> *kms)
>>       pm_runtime_put_sync(&dpu_kms->pdev->dev);
>>   }
>> +static int dpu_kms_check_mode_changed(struct msm_kms *kms, struct 
>> drm_atomic_state *state)
>> +{
>> +    struct drm_crtc_state *new_crtc_state;
>> +    struct drm_connector *connector;
>> +    struct drm_connector_state *new_conn_state;
>> +    int i;
>> +
>> +    for_each_new_connector_in_state(state, connector, new_conn_state, 
>> i) {
>> +        struct drm_encoder *encoder;
>> +
>> +        WARN_ON(!!new_conn_state->best_encoder != 
>> !!new_conn_state->crtc);
>> +
>> +        if (!new_conn_state->crtc || !new_conn_state->best_encoder)
>> +            continue;
>> +
>> +        new_crtc_state = drm_atomic_get_new_crtc_state(state, 
>> new_conn_state->crtc);
>> +
>> +        encoder = new_conn_state->best_encoder;
>> +
>> +        dpu_encoder_virt_check_mode_changed(encoder, new_crtc_state, 
>> new_conn_state);
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   static void dpu_kms_flush_commit(struct msm_kms *kms, unsigned 
>> crtc_mask)
>>   {
>>       struct dpu_kms *dpu_kms = to_dpu_kms(kms);
>> @@ -1049,6 +1074,7 @@ static const struct msm_kms_funcs kms_funcs = {
>>       .irq             = dpu_core_irq,
>>       .enable_commit   = dpu_kms_enable_commit,
>>       .disable_commit  = dpu_kms_disable_commit,
>> +    .check_mode_changed = dpu_kms_check_mode_changed,
>>       .flush_commit    = dpu_kms_flush_commit,
>>       .wait_flush      = dpu_kms_wait_flush,
>>       .complete_commit = dpu_kms_complete_commit,
>> diff --git a/drivers/gpu/drm/msm/msm_atomic.c 
>> b/drivers/gpu/drm/msm/msm_atomic.c
>> index 
>> a7a2384044ffdb13579cc9a10f56f8de9beca761..364df245e3a209094782ca1b47b752a729b32a5b 100644
>> --- a/drivers/gpu/drm/msm/msm_atomic.c
>> +++ b/drivers/gpu/drm/msm/msm_atomic.c
>> @@ -183,10 +183,16 @@ static unsigned get_crtc_mask(struct 
>> drm_atomic_state *state)
>>   int msm_atomic_check(struct drm_device *dev, struct drm_atomic_state 
>> *state)
>>   {
>> +    struct msm_drm_private *priv = dev->dev_private;
>> +    struct msm_kms *kms = priv->kms;
>>       struct drm_crtc_state *old_crtc_state, *new_crtc_state;
>>       struct drm_crtc *crtc;
>> -    int i;
>> +    int i, ret = 0;
>> +    /*
>> +     * FIXME: stop setting allow_modeset and move this check to the DPU
>> +     * driver.
>> +     */
>>       for_each_oldnew_crtc_in_state(state, crtc, old_crtc_state,
>>                         new_crtc_state, i) {
>>           if ((old_crtc_state->ctm && !new_crtc_state->ctm) ||
>> @@ -196,6 +202,11 @@ int msm_atomic_check(struct drm_device *dev, 
>> struct drm_atomic_state *state)
>>           }
>>       }
>> +    if (kms && kms->funcs && kms->funcs->check_mode_changed)
>> +        ret = kms->funcs->check_mode_changed(kms, state);
>> +    if (ret)
>> +        return ret;
>> +
>>       return drm_atomic_helper_check(dev, state);
>>   }
>> diff --git a/drivers/gpu/drm/msm/msm_kms.h 
>> b/drivers/gpu/drm/msm/msm_kms.h
>> index 
>> e60162744c669773b6e5aef824a173647626ab4e..ec2a75af89b09754faef1a07adc9338f7d78161e 100644
>> --- a/drivers/gpu/drm/msm/msm_kms.h
>> +++ b/drivers/gpu/drm/msm/msm_kms.h
>> @@ -59,6 +59,13 @@ struct msm_kms_funcs {
>>       void (*enable_commit)(struct msm_kms *kms);
>>       void (*disable_commit)(struct msm_kms *kms);
>> +    /**
>> +     * @check_mode_changed:
>> +     *
>> +     * Verify if the commit requires a full modeset on one of CRTCs.
>> +     */
>> +    int (*check_mode_changed)(struct msm_kms *kms, struct 
>> drm_atomic_state *state);
>> +
>>       /**
>>        * Prepare for atomic commit.  This is called after any previous
>>        * (async or otherwise) commit has completed.
>>