linux-kernel - [PATCH] DRM: VBLANK: provide valid timestamp for EVENT

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Date:   Wed, 26 Sep 2018 17:25:35 +0300
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Alexey Brodkin <alexey.brodkin@...opsys.com>,
        stable@...r.kernel.org,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Subject: [PATCH] DRM: VBLANK: provide valid timestamp for EVENT_FLIP

If driver/HW doesn't support vblank functionality (for example
UDL driver, ARCPGU driver, ...) we always have vblank->time == 0.
In result we always provide zero timestamp for
DRM_EVENT_FLIP_COMPLETE. This breaks userspace apps (for example
weston) which relies on timestamp value.

Setup time to provide valid timestamp for DRM_EVENT_FLIP_COMPLETE
event.

Cc: stable@...r.kernel.org
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
---
 drivers/gpu/drm/drm_vblank.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 28cdcf76b6f9..0d19aca48782 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -911,6 +911,15 @@ void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
 
 	if (dev->num_crtcs > 0) {
 		seq = drm_vblank_count_and_time(dev, pipe, &now);
+
+		/*
+		 * If driver/HW doesn't support vblank functionality we
+		 * always have vblank->time == 0. Setup time to provide valid
+		 * timestamp for DRM_EVENT_FLIP_COMPLETE event.
+		 */
+		if (!now && e->event.base.type == DRM_EVENT_FLIP_COMPLETE)
+			now = ktime_get();
+
 	} else {
 		seq = 0;
 
-- 
2.14.4