disp: msm: sde: avoid drm_crtc_vblank_on during seamless transition

When there is a race condition between DMS seamless transition and
drm_wait_vblank_ioctl, the latter gets deregistered for vblank
handle as drm_crtc_vblank_on call in crtc enbale increments vblank
count. This change avoids drm_crtc_vblank_on call during seamless
transition when crtc is already enabled as it is not required.

Change-Id: I0b9327a98cef00405b5b94e24a3fd15205339cfc
Signed-off-by: Raviteja Tamatam <[email protected]>

msm/sde/sde_crtc.c

@@ -4103,7 +4103,12 @@ static void sde_crtc_enable(struct drm_crtc *crtc,
 	SDE_EVT32_VERBOSE(DRMID(crtc));
 	sde_crtc = to_sde_crtc(crtc);
 
-	drm_crtc_vblank_on(crtc);
+	/*
+	 * Avoid drm_crtc_vblank_on during seamless DMS case
+	 * when CRTC is already in enabled state
+	 */
+	if (!sde_crtc->enabled)
+		drm_crtc_vblank_on(crtc);
 
 	mutex_lock(&sde_crtc->crtc_lock);
 	SDE_EVT32(DRMID(crtc), sde_crtc->enabled);