linux-kernel - [PATCH] drm/tilcdc: send vblank event when disabling crtc

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Message-Id: <20210129055831.1702862-1-quanyang.wang@windriver.com>
Date:   Fri, 29 Jan 2021 13:58:31 +0800
From:   quanyang.wang@...driver.com
To:     Jyri Sarha <jsarha@...com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Tomi Valkeinen <tomi.valkeinen@...com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        quanyang.wang@...driver.com
Subject: [PATCH] drm/tilcdc: send vblank event when disabling crtc

From: Quanyang Wang <quanyang.wang@...driver.com>

When run xrandr to change resolution on Beaglebone Black board, it will
print the error information:

root@...glebone:~# xrandr -display :0 --output HDMI-1 --mode 720x400
[drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:32:tilcdc crtc] commit wait timed out
[drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CONNECTOR:34:HDMI-A-1] commit wait timed out
[drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
[drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [PLANE:31:plane-0] commit wait timed out
tilcdc 4830e000.lcdc: already pending page flip!

This is because there is operation sequence as below:

drm_atomic_connector_commit_dpms(mode is DRM_MODE_DPMS_OFF):
    ...
    drm_atomic_helper_setup_commit <- init_completion(commit_A->flip_done)
    drm_atomic_helper_commit_tail
        tilcdc_crtc_atomic_disable
        tilcdc_plane_atomic_update <- drm_crtc_send_vblank_event in tilcdc_crtc_irq
                                      is skipped since tilcdc_crtc->enabled is 0
        tilcdc_crtc_atomic_flush   <- drm_crtc_send_vblank_event is skipped since
                                      crtc->state->event is set to be NULL in
                                      tilcdc_plane_atomic_update
drm_mode_setcrtc:
    ...
    drm_atomic_helper_setup_commit <- init_completion(commit_B->flip_done)
    drm_atomic_helper_wait_for_dependencies
        drm_crtc_commit_wait   <- wait for commit_A->flip_done completing

Just as shown above, the steps which could complete commit_A->flip_done
are all skipped and commit_A->flip_done will never be completed. This will
result a time-out ERROR when drm_crtc_commit_wait check the commit_A->flip_done.
So add drm_crtc_send_vblank_event in tilcdc_crtc_atomic_disable to
complete commit_A->flip_done.

Fixes: cb345decb4d2 ("drm/tilcdc: Use standard drm_atomic_helper_commit")
Signed-off-by: Quanyang Wang <quanyang.wang@...driver.com>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 30213708fc99..d99afd19ca08 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -515,6 +515,15 @@ static void tilcdc_crtc_off(struct drm_crtc *crtc, bool shutdown)

 	drm_crtc_vblank_off(crtc);

+	spin_lock_irq(&crtc->dev->event_lock);
+
+	if (crtc->state->event) {
+		drm_crtc_send_vblank_event(crtc, crtc->state->event);
+		crtc->state->event = NULL;
+	}
+
+	spin_unlock_irq(&crtc->dev->event_lock);
+
 	tilcdc_crtc_disable_irqs(dev);

 	pm_runtime_put_sync(dev->dev);
-- 
2.25.1