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From:   Rob Clark <robdclark@gmail.com>
To:     dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org
Cc:     Daniel Vetter <daniel@ffwll.ch>,
        =?UTF-8?q?Christian=20K=C3=B6nig?= 
        <ckoenig.leichtzumerken@gmail.com>,
        =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel@daenzer.net>,
        Pekka Paalanen <ppaalanen@gmail.com>,
        Rob Clark <robdclark@chromium.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH v3 2/9] drm/vblank: Add helper to get next vblank time
Date:   Fri,  3 Sep 2021 11:47:53 -0700
Message-Id: <20210903184806.1680887-3-robdclark@gmail.com>
In-Reply-To: <20210903184806.1680887-1-robdclark@gmail.com>
References: <20210903184806.1680887-1-robdclark@gmail.com>
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From: Rob Clark <robdclark@chromium.org>

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/drm_vblank.c | 32 ++++++++++++++++++++++++++++++++
 include/drm/drm_vblank.h     |  1 +
 2 files changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index b701cda86d0c..ec2732664b95 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -980,6 +980,38 @@ u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
 }
 EXPORT_SYMBOL(drm_crtc_vblank_count_and_time);
 
+/**
+ * drm_crtc_next_vblank_time - calculate the time of the next vblank
+ * @crtc: the crtc for which to calculate next vblank time
+ * @vblanktime: pointer to time to receive the next vblank timestamp.
+ *
+ * Calculate the expected time of the next vblank based on time of previous
+ * vblank and frame duration
+ */
+int drm_crtc_next_vblank_time(struct drm_crtc *crtc, ktime_t *vblanktime)
+{
+	unsigned int pipe = drm_crtc_index(crtc);
+	struct drm_vblank_crtc *vblank = &crtc->dev->vblank[pipe];
+	u64 count;
+
+	if (!vblank->framedur_ns)
+		return -EINVAL;
+
+	count = drm_vblank_count_and_time(crtc->dev, pipe, vblanktime);
+
+	/*
+	 * If we don't get a valid count, then we probably also don't
+	 * have a valid time:
+	 */
+	if (!count)
+		return -EINVAL;
+
+	*vblanktime = ktime_add(*vblanktime, ns_to_ktime(vblank->framedur_ns));
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_crtc_next_vblank_time);
+
 static void send_vblank_event(struct drm_device *dev,
 		struct drm_pending_vblank_event *e,
 		u64 seq, ktime_t now)
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index 733a3e2d1d10..a63bc2c92f3c 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -230,6 +230,7 @@ bool drm_dev_has_vblank(const struct drm_device *dev);
 u64 drm_crtc_vblank_count(struct drm_crtc *crtc);
 u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
 				   ktime_t *vblanktime);
+int drm_crtc_next_vblank_time(struct drm_crtc *crtc, ktime_t *vblanktime);
 void drm_crtc_send_vblank_event(struct drm_crtc *crtc,
 			       struct drm_pending_vblank_event *e);
 void drm_crtc_arm_vblank_event(struct drm_crtc *crtc,
-- 
2.31.1