Re: [PATCH 1/9] drm/msm/dpu: unwind async commit handling

Sean Paul
2019-08-29T13:04:51Z

On Tue, Aug 27, 2019 at 02:33:31PM -0700, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
>
> It attempted to avoid fps drops in the presence of cursor updates. But
> it is racing, and can result in hw updates after flush before vblank,
> which leads to underruns.
>
> Signed-off-by: Rob Clark <robdclark@chromium.org>

Reviewed-by: Sean Paul <sean@poorly.run>

> ---
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 41 ++++++++++-----------
> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h | 3 +-
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 39 +++++++-------------
> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 3 +-
> drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 5 +--
> drivers/gpu/drm/msm/msm_atomic.c | 3 +-
> 6 files changed, 37 insertions(+), 57 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index a52439e029c9..c3f7154017c4 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -610,7 +610,7 @@ static int _dpu_crtc_wait_for_frame_done(struct drm_crtc *crtc)
> return rc;
> }
>
> -void dpu_crtc_commit_kickoff(struct drm_crtc *crtc, bool async)
> +void dpu_crtc_commit_kickoff(struct drm_crtc *crtc)
> {
> struct drm_encoder *encoder;
> struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> @@ -636,35 +636,32 @@ void dpu_crtc_commit_kickoff(struct drm_crtc *crtc, bool async)
> crtc->state->encoder_mask)
> dpu_encoder_prepare_for_kickoff(encoder);
>
> - if (!async) {
> - /* wait for previous frame_event_done completion */
> - DPU_ATRACE_BEGIN("wait_for_frame_done_event");
> - ret = _dpu_crtc_wait_for_frame_done(crtc);
> - DPU_ATRACE_END("wait_for_frame_done_event");
> - if (ret) {
> - DPU_ERROR("crtc%d wait for frame done failed;frame_pending%d\n",
> - crtc->base.id,
> - atomic_read(&dpu_crtc->frame_pending));
> - goto end;
> - }
> + /* wait for previous frame_event_done completion */
> + DPU_ATRACE_BEGIN("wait_for_frame_done_event");
> + ret = _dpu_crtc_wait_for_frame_done(crtc);
> + DPU_ATRACE_END("wait_for_frame_done_event");
> + if (ret) {
> + DPU_ERROR("crtc%d wait for frame done failed;frame_pending%d\n",
> + crtc->base.id,
> + atomic_read(&dpu_crtc->frame_pending));
> + goto end;
> + }
>
> - if (atomic_inc_return(&dpu_crtc->frame_pending) == 1) {
> - /* acquire bandwidth and other resources */
> - DPU_DEBUG("crtc%d first commit\n", crtc->base.id);
> - } else
> - DPU_DEBUG("crtc%d commit\n", crtc->base.id);
> + if (atomic_inc_return(&dpu_crtc->frame_pending) == 1) {
> + /* acquire bandwidth and other resources */
> + DPU_DEBUG("crtc%d first commit\n", crtc->base.id);
> + } else
> + DPU_DEBUG("crtc%d commit\n", crtc->base.id);
>
> - dpu_crtc->play_count++;
> - }
> + dpu_crtc->play_count++;
>
> dpu_vbif_clear_errors(dpu_kms);
>
> drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state->encoder_mask)
> - dpu_encoder_kickoff(encoder, async);
> + dpu_encoder_kickoff(encoder);
>
> end:
> - if (!async)
> - reinit_completion(&dpu_crtc->frame_done_comp);
> + reinit_completion(&dpu_crtc->frame_done_comp);
> DPU_ATRACE_END("crtc_commit");
> }
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h
> index 5181f079a6a1..10f78459f6c2 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.h
> @@ -238,9 +238,8 @@ void dpu_crtc_vblank_callback(struct drm_crtc *crtc);
> /**
> * dpu_crtc_commit_kickoff - trigger kickoff of the commit for this crtc
> * @crtc: Pointer to drm crtc object
> - * @async: true if the commit is asynchronous, false otherwise
> */
> -void dpu_crtc_commit_kickoff(struct drm_crtc *crtc, bool async);
> +void dpu_crtc_commit_kickoff(struct drm_crtc *crtc);
>
> /**
> * dpu_crtc_complete_commit - callback signalling completion of current commit
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 627c57594221..ac2d534bf59e 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -1421,8 +1421,7 @@ static void dpu_encoder_off_work(struct work_struct *work)
> * extra_flush_bits: Additional bit mask to include in flush trigger
> */
> static void _dpu_encoder_trigger_flush(struct drm_encoder *drm_enc,
> - struct dpu_encoder_phys *phys, uint32_t extra_flush_bits,
> - bool async)
> + struct dpu_encoder_phys *phys, uint32_t extra_flush_bits)
> {
> struct dpu_hw_ctl *ctl;
> int pending_kickoff_cnt;
> @@ -1439,10 +1438,7 @@ static void _dpu_encoder_trigger_flush(struct drm_encoder *drm_enc,
> return;
> }
>
> - if (!async)
> - pending_kickoff_cnt = dpu_encoder_phys_inc_pending(phys);
> - else
> - pending_kickoff_cnt = atomic_read(&phys->pending_kickoff_cnt);
> + pending_kickoff_cnt = dpu_encoder_phys_inc_pending(phys);
>
> if (extra_flush_bits && ctl->ops.update_pending_flush)
> ctl->ops.update_pending_flush(ctl, extra_flush_bits);
> @@ -1553,8 +1549,7 @@ static void dpu_encoder_helper_hw_reset(struct dpu_encoder_phys *phys_enc)
> * a time.
> * dpu_enc: Pointer to virtual encoder structure
> */
> -static void _dpu_encoder_kickoff_phys(struct dpu_encoder_virt *dpu_enc,
> - bool async)
> +static void _dpu_encoder_kickoff_phys(struct dpu_encoder_virt *dpu_enc)
> {
> struct dpu_hw_ctl *ctl;
> uint32_t i, pending_flush;
> @@ -1581,13 +1576,12 @@ static void _dpu_encoder_kickoff_phys(struct dpu_encoder_virt *dpu_enc,
> * for async commits. So don't set this for async, since it'll
> * roll over to the next commit.
> */
> - if (!async && phys->split_role != ENC_ROLE_SLAVE)
> + if (phys->split_role != ENC_ROLE_SLAVE)
> set_bit(i, dpu_enc->frame_busy_mask);
>
> if (!phys->ops.needs_single_flush ||
> !phys->ops.needs_single_flush(phys))
> - _dpu_encoder_trigger_flush(&dpu_enc->base, phys, 0x0,
> - async);
> + _dpu_encoder_trigger_flush(&dpu_enc->base, phys, 0x0);
> else if (ctl->ops.get_pending_flush)
> pending_flush |= ctl->ops.get_pending_flush(ctl);
> }
> @@ -1597,7 +1591,7 @@ static void _dpu_encoder_kickoff_phys(struct dpu_encoder_virt *dpu_enc,
> _dpu_encoder_trigger_flush(
> &dpu_enc->base,
> dpu_enc->cur_master,
> - pending_flush, async);
> + pending_flush);
> }
>
> _dpu_encoder_trigger_start(dpu_enc->cur_master);
> @@ -1815,11 +1809,12 @@ void dpu_encoder_prepare_for_kickoff(struct drm_encoder *drm_enc)
> }
> }
>
> -void dpu_encoder_kickoff(struct drm_encoder *drm_enc, bool async)
> +void dpu_encoder_kickoff(struct drm_encoder *drm_enc)
> {
> struct dpu_encoder_virt *dpu_enc;
> struct dpu_encoder_phys *phys;
> ktime_t wakeup_time;
> + unsigned long timeout_ms;
> unsigned int i;
>
> DPU_ATRACE_BEGIN("encoder_kickoff");
> @@ -1827,23 +1822,15 @@ void dpu_encoder_kickoff(struct drm_encoder *drm_enc, bool async)
>
> trace_dpu_enc_kickoff(DRMID(drm_enc));
>
> - /*
> - * Asynchronous frames don't handle FRAME_DONE events. As such, they
> - * shouldn't enable the frame_done watchdog since it will always time
> - * out.
> - */
> - if (!async) {
> - unsigned long timeout_ms;
> - timeout_ms = DPU_ENCODER_FRAME_DONE_TIMEOUT_FRAMES * 1000 /
> + timeout_ms = DPU_ENCODER_FRAME_DONE_TIMEOUT_FRAMES * 1000 /
> drm_mode_vrefresh(&drm_enc->crtc->state->adjusted_mode);
>
> - atomic_set(&dpu_enc->frame_done_timeout_ms, timeout_ms);
> - mod_timer(&dpu_enc->frame_done_timer,
> - jiffies + msecs_to_jiffies(timeout_ms));
> - }
> + atomic_set(&dpu_enc->frame_done_timeout_ms, timeout_ms);
> + mod_timer(&dpu_enc->frame_done_timer,
> + jiffies + msecs_to_jiffies(timeout_ms));
>
> /* All phys encs are ready to go, trigger the kickoff */
> - _dpu_encoder_kickoff_phys(dpu_enc, async);
> + _dpu_encoder_kickoff_phys(dpu_enc);
>
> /* allow phys encs to handle any post-kickoff business */
> for (i = 0; i < dpu_enc->num_phys_encs; i++) {
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> index 997d131c2440..8465b37adf3b 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
> @@ -82,9 +82,8 @@ void dpu_encoder_trigger_kickoff_pending(struct drm_encoder *encoder);
> * dpu_encoder_kickoff - trigger a double buffer flip of the ctl path
> * (i.e. ctl flush and start) immediately.
> * @encoder: encoder pointer
> - * @async: true if this is an asynchronous commit
> */
> -void dpu_encoder_kickoff(struct drm_encoder *encoder, bool async);
> +void dpu_encoder_kickoff(struct drm_encoder *encoder);
>
> /**
> * dpu_encoder_wait_for_event - Waits for encoder events
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index b8d264bd15df..31454cc5d8c5 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -298,7 +298,7 @@ void dpu_kms_encoder_enable(struct drm_encoder *encoder)
> continue;
>
> trace_dpu_kms_enc_enable(DRMID(crtc));
> - dpu_crtc_commit_kickoff(crtc, false);
> + dpu_crtc_commit_kickoff(crtc);
> }
> }
>
> @@ -315,8 +315,7 @@ static void dpu_kms_commit(struct msm_kms *kms, struct drm_atomic_state *state)
>
> if (crtc->state->active) {
> trace_dpu_kms_commit(DRMID(crtc));
> - dpu_crtc_commit_kickoff(crtc,
> - state->legacy_cursor_update);
> + dpu_crtc_commit_kickoff(crtc);
> }
> }
> }
> diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
> index dd16babdd8c0..e5aae1645933 100644
> --- a/drivers/gpu/drm/msm/msm_atomic.c
> +++ b/drivers/gpu/drm/msm/msm_atomic.c
> @@ -70,8 +70,7 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
> kms->funcs->commit(kms, state);
> }
>
> - if (!state->legacy_cursor_update)
> - msm_atomic_wait_for_commit_done(dev, state);
> + msm_atomic_wait_for_commit_done(dev, state);
>
> kms->funcs->complete_commit(kms, state);
>
> --
> 2.21.0
>

--
Sean Paul, Software Engineer, Google / Chromium OS