[PATCH 01/15] drm/vblank: Allow dynamic per-crtc max_vblank_count

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

On i965gm we need to adjust max_vblank_count dynamically
depending on whether the TV encoder is used or not. To
that end add a per-crtc max_vblank_count that takes
precedence over its device wide counterpart. The driver
can now call drm_crtc_set_max_vblank_count() to configure
the per-crtc value before calling drm_vblank_on().

Also looks like there was some discussion about exynos needing
similar treatment.

Cc: stable at vger.kernel.org
Cc: Inki Dae <inki.dae at samsung.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/drm_vblank.c | 39 ++++++++++++++++++++++++++++++++----
 include/drm/drm_vblank.h     |  8 ++++++++
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 98e091175921..c3abbdca8aba 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -105,13 +105,20 @@ static void store_vblank(struct drm_device *dev, unsigned int pipe,
 	write_sequnlock(&vblank->seqlock);
 }
 
+static u32 drm_max_vblank_count(struct drm_device *dev, unsigned int pipe)
+{
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
+
+	return vblank->max_vblank_count ?: dev->max_vblank_count;
+}
+
 /*
  * "No hw counter" fallback implementation of .get_vblank_counter() hook,
  * if there is no useable hardware frame counter available.
  */
 static u32 drm_vblank_no_hw_counter(struct drm_device *dev, unsigned int pipe)
 {
-	WARN_ON_ONCE(dev->max_vblank_count != 0);
+	WARN_ON_ONCE(drm_max_vblank_count(dev, pipe) != 0);
 	return 0;
 }
 
@@ -198,6 +205,7 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
 	ktime_t t_vblank;
 	int count = DRM_TIMESTAMP_MAXRETRIES;
 	int framedur_ns = vblank->framedur_ns;
+	u32 max_vblank_count = drm_max_vblank_count(dev, pipe);
 
 	/*
 	 * Interrupts were disabled prior to this call, so deal with counter
@@ -216,9 +224,9 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
 		rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, in_vblank_irq);
 	} while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);
 
-	if (dev->max_vblank_count != 0) {
+	if (max_vblank_count) {
 		/* trust the hw counter when it's around */
-		diff = (cur_vblank - vblank->last) & dev->max_vblank_count;
+		diff = (cur_vblank - vblank->last) & max_vblank_count;
 	} else if (rc && framedur_ns) {
 		u64 diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
 
@@ -258,7 +266,8 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
 		      pipe, vblank->count, diff, cur_vblank, vblank->last);
 
 	if (diff == 0) {
-		WARN_ON_ONCE(cur_vblank != vblank->last);
+		WARN_ON_ONCE(max_vblank_count &&
+			     cur_vblank != vblank->last);
 		return;
 	}
 
@@ -1204,6 +1213,28 @@ void drm_crtc_vblank_reset(struct drm_crtc *crtc)
 }
 EXPORT_SYMBOL(drm_crtc_vblank_reset);
 
+/**
+ * drm_crtc_set_max_vblank_count - configure the hw max vblank counter value
+ * @crtc: CRTC in question
+ * @max_vblank_count: max hardware vblank counter value
+ *
+ * Update the maximum hardware vblank counter value for @crtc. Useful
+ * for hardware where the operation of the hardware vblank counter
+ * depends on the active display configuration.
+ *
+ * If used, must be called before drm_vblank_on().
+ */
+void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
+				   u32 max_vblank_count)
+{
+	struct drm_device *dev = crtc->dev;
+	unsigned int pipe = drm_crtc_index(crtc);
+	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
+
+	vblank->max_vblank_count = max_vblank_count;
+}
+EXPORT_SYMBOL(drm_crtc_set_max_vblank_count);
+
 /**
  * drm_crtc_vblank_on - enable vblank events on a CRTC
  * @crtc: CRTC in question
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index 6ad9630d4f48..ecb2cf9913e2 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -128,6 +128,12 @@ struct drm_vblank_crtc {
 	 * @last: Protected by &drm_device.vbl_lock, used for wraparound handling.
 	 */
 	u32 last;
+	/**
+	 * @max_vblank_count: Maximum value of the hardware vblank counter.
+	 * If non-zero this takes precedence over &drm_device.max_vblank_count
+	 * for this crtc. Otherwise &drm_device.max_vblank_count is used.
+	 */
+	u32 max_vblank_count;
 	/**
 	 * @inmodeset: Tracks whether the vblank is disabled due to a modeset.
 	 * For legacy driver bit 2 additionally tracks whether an additional
@@ -206,4 +212,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev,
 void drm_calc_timestamping_constants(struct drm_crtc *crtc,
 				     const struct drm_display_mode *mode);
 wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc);
+void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,
+				   u32 max_vblank_count);
 #endif
-- 
2.18.1