RE: [PATCH v7 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and get crtc from connector state instead of dpu_enc

[Vinod Polimera]

> -----Original Message-----
> From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> Sent: Tuesday, September 13, 2022 10:36 PM
> To: Vinod Polimera (QUIC) <quic_vpolimer@xxxxxxxxxxx>; dri-
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> Subject: Re: [PATCH v7 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and
> get crtc from connector state instead of dpu_enc
> 
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> 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@xxxxxxxxxxx>
> >> ---
> >>   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/
As this is in interrupt context , we cannot use modeset lock here and connector does not have the spinlock to protect state.
since state swap happens after commit to hw done, which is after vblank processing, i was thinking it should be okay to drop the spinlock  while accessing connector state.
I have updated the patch with the changes in v8, please do review.
> 
> --
> With best wishes
> Dmitry
Thanks
Vinod P.