RE: [PATCH v8 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and get crtc from connector state instead of dpu_enc

From: Vinod Polimera
Date: Tue Nov 01 2022 - 07:16:54 EST

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> -----Original Message-----
> From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> Sent: Thursday, October 27, 2022 11:11 PM
> To: Vinod Polimera <vpolimer@xxxxxxxxxxxxxxxx>; Vinod Polimera (QUIC)
> <quic_vpolimer@xxxxxxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-arm-
> msm@xxxxxxxxxxxxxxx; freedreno@xxxxxxxxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; robdclark@xxxxxxxxx;
> dianders@xxxxxxxxxxxx; swboyd@xxxxxxxxxxxx; Kalyan Thota (QUIC)
> <quic_kalyant@xxxxxxxxxxx>; Kuogee Hsieh (QUIC)
> <quic_khsieh@xxxxxxxxxxx>; Vishnuvardhan Prodduturi (QUIC)
> <quic_vproddut@xxxxxxxxxxx>; Bjorn Andersson (QUIC)
> <quic_bjorande@xxxxxxxxxxx>; Aravind Venkateswaran (QUIC)
> <quic_aravindh@xxxxxxxxxxx>; Abhinav Kumar (QUIC)
> <quic_abhinavk@xxxxxxxxxxx>; Sankeerth Billakanti (QUIC)
> <quic_sbillaka@xxxxxxxxxxx>
> Subject: Re: [PATCH v8 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and
> get crtc from connector state instead of dpu_enc
>
> WARNING: This email originated from outside of Qualcomm. Please be wary
> of any links or attachments, and do not enable macros.
>
> On 27/10/2022 16:34, Vinod Polimera wrote:
> >> -----Original Message-----
> >> From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> >> Sent: Monday, October 24, 2022 8:52 PM
> >> To: Vinod Polimera (QUIC) <quic_vpolimer@xxxxxxxxxxx>; dri-
> >> devel@xxxxxxxxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx;
> >> freedreno@xxxxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx
> >> Cc: linux-kernel@xxxxxxxxxxxxxxx; robdclark@xxxxxxxxx;
> >> dianders@xxxxxxxxxxxx; swboyd@xxxxxxxxxxxx; Kalyan Thota (QUIC)
> >> <quic_kalyant@xxxxxxxxxxx>; Kuogee Hsieh (QUIC)
> >> <quic_khsieh@xxxxxxxxxxx>; Vishnuvardhan Prodduturi (QUIC)
> >> <quic_vproddut@xxxxxxxxxxx>; Bjorn Andersson (QUIC)
> >> <quic_bjorande@xxxxxxxxxxx>; Aravind Venkateswaran (QUIC)
> >> <quic_aravindh@xxxxxxxxxxx>; Abhinav Kumar (QUIC)
> >> <quic_abhinavk@xxxxxxxxxxx>; Sankeerth Billakanti (QUIC)
> >> <quic_sbillaka@xxxxxxxxxxx>
> >> Subject: Re: [PATCH v8 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc
> and
> >> get crtc from connector state instead of dpu_enc
> >>
> >> WARNING: This email originated from outside of Qualcomm. Please be
> wary
> >> of any links or attachments, and do not enable macros.
> >>
> >> On 12/10/2022 15:02, 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 | 42 +++++++++-----
> ----
> >> -----------
> >>> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 8 ------
> >>> 3 files changed, 13 insertions(+), 41 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..d05b353 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;
> >>> @@ -1288,7 +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;
> >>> - unsigned long lock_flags;
> >>> + struct drm_crtc *crtc;
> >>>
> >>> if (!drm_enc || !phy_enc)
> >>> return;
> >>> @@ -1296,12 +1290,13 @@ static void
> dpu_encoder_vblank_callback(struct
> >> drm_encoder *drm_enc,
> >>> DPU_ATRACE_BEGIN("encoder_vblank_callback");
> >>> dpu_enc = to_dpu_encoder_virt(drm_enc);
> >>>
> >>> - atomic_inc(&phy_enc->vsync_cnt);
> >>> + if (!dpu_enc->connector || !dpu_enc->connector->state ||
> >>> + !dpu_enc->connector->state->crtc)
> >>> + return;
> >>>
> >>> - spin_lock_irqsave(&dpu_enc->enc_spinlock, lock_flags);
> >>> - if (dpu_enc->crtc)
> >>> - dpu_crtc_vblank_callback(dpu_enc->crtc);
> >>> - spin_unlock_irqrestore(&dpu_enc->enc_spinlock, lock_flags);
> >>> + atomic_inc(&phy_enc->vsync_cnt);
> >>> + crtc = dpu_enc->connector->state->crtc;
> >>> + dpu_crtc_vblank_callback(crtc);
> >>
> >> So, what if the user commits the mode setting change on another CPU,
> >> while we are handling the vblank callback here? Can this happen?
> >>
> > If user issues a commit on another CPU, it will wait in the
> drm_atomic_helper_swap_state
> > as drm_atomic_helper_commit_hw_done which does the
> complete_all(&commit->hw_done)
> > for the current commit didn't finish yet.
>
> Yes. But there is no interlock between commit->hw_done and vblank IRQ
> processing, isn't it? This call happens when DPU processes the vblank
> IRQ, so nobody stops other core from swapping the encode state on
> another core.

https://patchwork.kernel.org/project/linux-arm-msm/patch/1667300361-14572-1-git-send-email-quic_kalyant@xxxxxxxxxxx/
(drm/msm/disp/dpu1: register crtc color management to first crtc in the list)

The above patch pins 1 crtc to 1 encoder, so it will be safe to assume that crtc wont change.

> >>>
> >>> DPU_ATRACE_END("encoder_vblank_callback");
> >>> }
> >> --
> >> With best wishes
> >> Dmitry
> >
> > Thanks,
> > Vinod P.
>
> --
> With best wishes
> Dmitry

Thanks,
Vinod P.

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