linux-kernel - [PATCH] drm/komeda: Fix FLIP_COMPLETE timestamp on CRTC enable

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Message-ID: <20190919132759.18358-1-mihail.atanassov@arm.com>
Date:   Thu, 19 Sep 2019 13:30:02 +0000
From:   Mihail Atanassov <Mihail.Atanassov@....com>
To:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
CC:     Mihail Atanassov <Mihail.Atanassov@....com>, nd <nd@....com>,
        Daniel Vetter <daniel@...ll.ch>,
        Liviu Dudau <Liviu.Dudau@....com>,
        "james qian wang (Arm Technology China)" <james.qian.wang@....com>,
        Liviu Dudau <Liviu.Dudau@....com>,
        Brian Starkey <Brian.Starkey@....com>,
        David Airlie <airlied@...ux.ie>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] drm/komeda: Fix FLIP_COMPLETE timestamp on CRTC enable

When initially turning a crtc on, drm_reset_vblank_timestamp will
set the vblank timestamp to 0 for any driver that doesn't provide
a ->get_vblank_timestamp() hook.

Unfortunately, the FLIP_COMPLETE event depends on that timestamp,
and the only way to regenerate a valid one is to have vblank
interrupts enabled and have a valid in-ISR call to
drm_crtc_handle_vblank.

Wrap the call to komeda_crtc_do_flush in ->atomic_enable() with a
drm_crtc_vblank_{get,put} pair so we can have a vblank ISR prior to
the FLIP_COMPLETE ISR (or more likely, they'll get handled in the same
ISR, which is equally valid).

Cc: Daniel Vetter <daniel@...ll.ch>
Cc: Liviu Dudau <Liviu.Dudau@....com>
Signed-off-by: Mihail Atanassov <mihail.atanassov@....com>
---
 drivers/gpu/drm/arm/display/komeda/komeda_crtc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
index f4400788ab94..87420a767bc4 100644
--- a/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
+++ b/drivers/gpu/drm/arm/display/komeda/komeda_crtc.c
@@ -258,7 +258,9 @@ komeda_crtc_atomic_enable(struct drm_crtc *crtc,
 {
 	komeda_crtc_prepare(to_kcrtc(crtc));
 	drm_crtc_vblank_on(crtc);
+	WARN_ON(drm_crtc_vblank_get(crtc));
 	komeda_crtc_do_flush(crtc, old);
+	drm_crtc_vblank_put(crtc);
 }
 
 static void
-- 
2.23.0