[PATCH v9 10/15] drm/vblank: Add helper to get next vblank time

Rob Clark
2023-03-02T23:55:00Z

From: Rob Clark <robdclark@chromium.org>

Will be used in the next commit to set a deadline on fences that an
atomic update is waiting on.

v2: Calculate time at *start* of vblank period, not end
v3: Fix kbuild complaints

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Mario Kleiner <mario.kleiner.de@gmail.com>
---
drivers/gpu/drm/drm_vblank.c | 53 ++++++++++++++++++++++++++++++------
include/drm/drm_vblank.h | 1 +
2 files changed, 45 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 2ff31717a3de..299fa2a19a90 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -844,10 +844,9 @@ bool drm_crtc_vblank_helper_get_vblank_timestamp(struct drm_crtc *crtc,
EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp);

/**
- * drm_get_last_vbltimestamp - retrieve raw timestamp for the most recent
- * vblank interval
- * @dev: DRM device
- * @pipe: index of CRTC whose vblank timestamp to retrieve
+ * drm_crtc_get_last_vbltimestamp - retrieve raw timestamp for the most
+ * recent vblank interval
+ * @crtc: CRTC whose vblank timestamp to retrieve
* @tvblank: Pointer to target time which should receive the timestamp
* @in_vblank_irq:
* True when called from drm_crtc_handle_vblank(). Some drivers
@@ -865,10 +864,9 @@ EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp);
* True if timestamp is considered to be very precise, false otherwise.
*/
static bool
-drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
- ktime_t *tvblank, bool in_vblank_irq)
+drm_crtc_get_last_vbltimestamp(struct drm_crtc *crtc, ktime_t *tvblank,
+ bool in_vblank_irq)
{
- struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
bool ret = false;

/* Define requested maximum error on timestamps (nanoseconds). */
@@ -876,8 +874,6 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,

/* Query driver if possible and precision timestamping enabled. */
if (crtc && crtc->funcs->get_vblank_timestamp && max_error > 0) {
- struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
-
ret = crtc->funcs->get_vblank_timestamp(crtc, &max_error,
tvblank, in_vblank_irq);
}
@@ -891,6 +887,15 @@ drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
return ret;
}

+static bool
+drm_get_last_vbltimestamp(struct drm_device *dev, unsigned int pipe,
+ ktime_t *tvblank, bool in_vblank_irq)
+{
+ struct drm_crtc *crtc = drm_crtc_from_index(dev, pipe);
+
+ return drm_crtc_get_last_vbltimestamp(crtc, tvblank, in_vblank_irq);
+}
+
/**
* drm_crtc_vblank_count - retrieve "cooked" vblank counter value
* @crtc: which counter to retrieve
@@ -980,6 +985,36 @@ u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,
}
EXPORT_SYMBOL(drm_crtc_vblank_count_and_time);

+/**
+ * drm_crtc_next_vblank_start - 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 start of the next vblank period,
+ * based on time of previous vblank and frame duration
+ */
+int drm_crtc_next_vblank_start(struct drm_crtc *crtc, ktime_t *vblanktime)
+{
+ unsigned int pipe = drm_crtc_index(crtc);
+ struct drm_vblank_crtc *vblank = &crtc->dev->vblank[pipe];
+ struct drm_display_mode *mode = &vblank->hwmode;
+ u64 vblank_start;
+
+ if (!vblank->framedur_ns || !vblank->linedur_ns)
+ return -EINVAL;
+
+ if (!drm_crtc_get_last_vbltimestamp(crtc, vblanktime, false))
+ return -EINVAL;
+
+ vblank_start = DIV_ROUND_DOWN_ULL(
+ (u64)vblank->framedur_ns * mode->crtc_vblank_start,
+ mode->crtc_vtotal);
+ *vblanktime = ktime_add(*vblanktime, ns_to_ktime(vblank_start));
+
+ return 0;
+}
+EXPORT_SYMBOL(drm_crtc_next_vblank_start);
+
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..7f3957943dd1 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_start(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,
--
2.39.1