diff options
Diffstat (limited to 'drivers/gpu/drm/drm_irq.c')
| -rw-r--r-- | drivers/gpu/drm/drm_irq.c | 109 |
1 files changed, 65 insertions, 44 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index af9662e58..b50fa0afd 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -74,6 +74,36 @@ module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600); module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600); module_param_named(timestamp_monotonic, drm_timestamp_monotonic, int, 0600); +static void store_vblank(struct drm_device *dev, int crtc, + u32 vblank_count_inc, + struct timeval *t_vblank) +{ + struct drm_vblank_crtc *vblank = &dev->vblank[crtc]; + u32 tslot; + + assert_spin_locked(&dev->vblank_time_lock); + + if (t_vblank) { + /* All writers hold the spinlock, but readers are serialized by + * the latching of vblank->count below. + */ + tslot = vblank->count + vblank_count_inc; + vblanktimestamp(dev, crtc, tslot) = *t_vblank; + } + + /* + * vblank timestamp updates are protected on the write side with + * vblank_time_lock, but on the read side done locklessly using a + * sequence-lock on the vblank counter. Ensure correct ordering using + * memory barrriers. We need the barrier both before and also after the + * counter update to synchronize with the next timestamp write. + * The read-side barriers for this are in drm_vblank_count_and_time. + */ + smp_wmb(); + vblank->count += vblank_count_inc; + smp_wmb(); +} + /** * drm_update_vblank_count - update the master vblank counter * @dev: DRM device @@ -93,14 +123,14 @@ module_param_named(timestamp_monotonic, drm_timestamp_monotonic, int, 0600); static void drm_update_vblank_count(struct drm_device *dev, int crtc) { struct drm_vblank_crtc *vblank = &dev->vblank[crtc]; - u32 cur_vblank, diff, tslot; + u32 cur_vblank, diff; bool rc; struct timeval t_vblank; /* * Interrupts were disabled prior to this call, so deal with counter * wrap if needed. - * NOTE! It's possible we lost a full dev->max_vblank_count events + * NOTE! It's possible we lost a full dev->max_vblank_count + 1 events * here if the register is small or we had vblank interrupts off for * a long time. * @@ -117,7 +147,7 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc) /* Deal with counter wrap */ diff = cur_vblank - vblank->last; if (cur_vblank < vblank->last) { - diff += dev->max_vblank_count; + diff += dev->max_vblank_count + 1; DRM_DEBUG("last_vblank[%d]=0x%x, cur_vblank=0x%x => diff=0x%x\n", crtc, vblank->last, cur_vblank, diff); @@ -129,17 +159,15 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc) if (diff == 0) return; - /* Reinitialize corresponding vblank timestamp if high-precision query - * available. Skip this step if query unsupported or failed. Will - * reinitialize delayed at next vblank interrupt in that case and - * assign 0 for now, to mark the vblanktimestamp as invalid. + /* + * Only reinitialize corresponding vblank timestamp if high-precision query + * available and didn't fail. Otherwise reinitialize delayed at next vblank + * interrupt and assign 0 for now, to mark the vblanktimestamp as invalid. */ - tslot = atomic_read(&vblank->count) + diff; - vblanktimestamp(dev, crtc, tslot) = rc ? t_vblank : (struct timeval) {0, 0}; + if (!rc) + t_vblank = (struct timeval) {0, 0}; - smp_mb__before_atomic(); - atomic_add(diff, &vblank->count); - smp_mb__after_atomic(); + store_vblank(dev, crtc, diff, &t_vblank); } /* @@ -217,7 +245,7 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc) /* Compute time difference to stored timestamp of last vblank * as updated by last invocation of drm_handle_vblank() in vblank irq. */ - vblcount = atomic_read(&vblank->count); + vblcount = vblank->count; diff_ns = timeval_to_ns(&tvblank) - timeval_to_ns(&vblanktimestamp(dev, crtc, vblcount)); @@ -233,17 +261,8 @@ static void vblank_disable_and_save(struct drm_device *dev, int crtc) * available. In that case we can't account for this and just * hope for the best. */ - if (vblrc && (abs64(diff_ns) > 1000000)) { - /* Store new timestamp in ringbuffer. */ - vblanktimestamp(dev, crtc, vblcount + 1) = tvblank; - - /* Increment cooked vblank count. This also atomically commits - * the timestamp computed above. - */ - smp_mb__before_atomic(); - atomic_inc(&vblank->count); - smp_mb__after_atomic(); - } + if (vblrc && (abs64(diff_ns) > 1000000)) + store_vblank(dev, crtc, 1, &tvblank); spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags); } @@ -336,6 +355,13 @@ int drm_vblank_init(struct drm_device *dev, int num_crtcs) else DRM_INFO("No driver support for vblank timestamp query.\n"); + /* Must have precise timestamping for reliable vblank instant disable */ + if (dev->vblank_disable_immediate && !dev->driver->get_vblank_timestamp) { + dev->vblank_disable_immediate = false; + DRM_INFO("Setting vblank_disable_immediate to false because " + "get_vblank_timestamp == NULL\n"); + } + dev->vblank_disable_allowed = false; return 0; @@ -851,7 +877,7 @@ u32 drm_vblank_count(struct drm_device *dev, int crtc) if (WARN_ON(crtc >= dev->num_crtcs)) return 0; - return atomic_read(&vblank->count); + return vblank->count; } EXPORT_SYMBOL(drm_vblank_count); @@ -896,16 +922,17 @@ u32 drm_vblank_count_and_time(struct drm_device *dev, int crtc, if (WARN_ON(crtc >= dev->num_crtcs)) return 0; - /* Read timestamp from slot of _vblank_time ringbuffer - * that corresponds to current vblank count. Retry if - * count has incremented during readout. This works like - * a seqlock. + /* + * Vblank timestamps are read lockless. To ensure consistency the vblank + * counter is rechecked and ordering is ensured using memory barriers. + * This works like a seqlock. The write-side barriers are in store_vblank. */ do { - cur_vblank = atomic_read(&vblank->count); + cur_vblank = vblank->count; + smp_rmb(); *vblanktime = vblanktimestamp(dev, crtc, cur_vblank); smp_rmb(); - } while (cur_vblank != atomic_read(&vblank->count)); + } while (cur_vblank != vblank->count); return cur_vblank; } @@ -1029,6 +1056,9 @@ int drm_vblank_get(struct drm_device *dev, int crtc) unsigned long irqflags; int ret = 0; + if (!dev->num_crtcs) + return -EINVAL; + if (WARN_ON(crtc >= dev->num_crtcs)) return -EINVAL; @@ -1714,7 +1744,7 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc) */ /* Get current timestamp and count. */ - vblcount = atomic_read(&vblank->count); + vblcount = vblank->count; drm_get_last_vbltimestamp(dev, crtc, &tvblank, DRM_CALLED_FROM_VBLIRQ); /* Compute time difference to timestamp of last vblank */ @@ -1730,20 +1760,11 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc) * e.g., due to spurious vblank interrupts. We need to * ignore those for accounting. */ - if (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) { - /* Store new timestamp in ringbuffer. */ - vblanktimestamp(dev, crtc, vblcount + 1) = tvblank; - - /* Increment cooked vblank count. This also atomically commits - * the timestamp computed above. - */ - smp_mb__before_atomic(); - atomic_inc(&vblank->count); - smp_mb__after_atomic(); - } else { + if (abs64(diff_ns) > DRM_REDUNDANT_VBLIRQ_THRESH_NS) + store_vblank(dev, crtc, 1, &tvblank); + else DRM_DEBUG("crtc %d: Redundant vblirq ignored. diff_ns = %d\n", crtc, (int) diff_ns); - } spin_unlock(&dev->vblank_time_lock); |