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-rw-r--r--drivers/gpu/drm/drm_vblank.c45
-rw-r--r--include/drm/drm_device.h6
-rw-r--r--include/drm/drm_vblank.h22
3 files changed, 70 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 98e091175921..cde71ee95a8f 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));
@@ -1205,6 +1213,37 @@ 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
+ * at runtime. Useful for hardware where the operation of the
+ * hardware vblank counter depends on the currently active
+ * display configuration.
+ *
+ * For example, if the hardware vblank counter does not work
+ * when a specific connector is active the maximum can be set
+ * to zero. And when that specific connector isn't active the
+ * maximum can again be set to the appropriate non-zero value.
+ *
+ * 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];
+
+ WARN_ON(dev->max_vblank_count);
+ WARN_ON(!READ_ONCE(vblank->inmodeset));
+
+ 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_device.h b/include/drm/drm_device.h
index a6f8e5abb66f..d5e092dccf3e 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -240,6 +240,12 @@ struct drm_device {
* races and imprecision over longer time periods, hence exposing a
* hardware vblank counter is always recommended.
*
+ * This is the statically configured device wide maximum. The driver
+ * can instead choose to use a runtime configurable per-crtc value
+ * &drm_vblank_crtc.max_vblank_count, in which case @max_vblank_count
+ * must be left at zero. See drm_crtc_set_max_vblank_count() on how
+ * to use the per-crtc value.
+ *
* If non-zero, &drm_crtc_funcs.get_vblank_counter must be set.
*/
u32 max_vblank_count;
diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h
index 6ad9630d4f48..e528bb2f659d 100644
--- a/include/drm/drm_vblank.h
+++ b/include/drm/drm_vblank.h
@@ -129,6 +129,26 @@ struct drm_vblank_crtc {
*/
u32 last;
/**
+ * @max_vblank_count:
+ *
+ * Maximum value of the vblank registers for this crtc. This value +1
+ * will result in a wrap-around of the vblank register. It is used
+ * by the vblank core to handle wrap-arounds.
+ *
+ * If set to zero the vblank core will try to guess the elapsed vblanks
+ * between times when the vblank interrupt is disabled through
+ * high-precision timestamps. That approach is suffering from small
+ * races and imprecision over longer time periods, hence exposing a
+ * hardware vblank counter is always recommended.
+ *
+ * This is the runtime configurable per-crtc maximum set through
+ * drm_crtc_set_max_vblank_count(). If this is used the driver
+ * must leave the device wide &drm_device.max_vblank_count at zero.
+ *
+ * If non-zero, &drm_crtc_funcs.get_vblank_counter must be set.
+ */
+ 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
* temporary vblank reference has been acquired to paper over the
@@ -206,4 +226,6 @@ 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