Re: [PATCH 1/3] drm/vblank: Introduce drm_crtc_vblank_get_accurate()

On Fri, Jun 30, 2017 at 05:18:41PM +0300, ville.syrjala@linux.intel.com wrote:

From: Ville Syrjälä ville.syrjala@linux.intel.com

Add drm_crtc_vblank_get_accurate() which is the same as drm_crtc_vblank_get() except that it will forcefully update the the current vblank counter/timestamp value even if the interrupt is already enabled.

And we'll switch drm_wait_one_vblank() over to using it to make sure it will really wait at least one vblank even if it races with the irq handler.

Cc: Daniel Vetter daniel@ffwll.ch Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com

Hm, I just thought of doing an s/drm_vblank_count/drm_crtc_accurate_vblank_count/ in drm_crtc_arm_vblank_event.

What does this buy us above&beyond the other patch? And why isn't vblank_get accurate always?

/me confused

Cheers, Daniel

---

drivers/gpu/drm/drm_vblank.c | 37 ++++++++++++++++++++++++++++++++----- include/drm/drm_vblank.h | 1 + 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 823c853de052..c57383b8753b 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -955,7 +955,8 @@ static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe) return ret; }

-static int drm_vblank_get(struct drm_device *dev, unsigned int pipe) +static int drm_vblank_get(struct drm_device *dev, unsigned int pipe,

• 	  bool force_update)
  

{ struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; unsigned long irqflags; @@ -975,6 +976,10 @@ static int drm_vblank_get(struct drm_device *dev, unsigned int pipe) if (!vblank->enabled) { atomic_dec(&vblank->refcount); ret = -EINVAL;

• } else if (force_update) {
  

• 	spin_lock(&dev->vblank_time_lock);
  

• 	drm_update_vblank_count(dev, pipe, false);
  

• 	spin_unlock(&dev->vblank_time_lock);
  

  } } spin_unlock_irqrestore(&dev->vbl_lock, irqflags);

@@ -994,10 +999,32 @@ static int drm_vblank_get(struct drm_device *dev, unsigned int pipe) */ int drm_crtc_vblank_get(struct drm_crtc *crtc) {

• return drm_vblank_get(crtc->dev, drm_crtc_index(crtc));

• return drm_vblank_get(crtc->dev, drm_crtc_index(crtc), false);

} EXPORT_SYMBOL(drm_crtc_vblank_get);

+/**

• • drm_crtc_vblank_get_accurate - get a reference count on vblank events and

• •                            make sure the counter is uptodate
    

• • @crtc: which CRTC to own
• • Acquire a reference count on vblank events to avoid having them disabled
• • while in use.
• • Also make sure the current vblank counter is value is fully up to date
• • even if we're already past the start of vblank but the irq hasn't fired
• • yet, which may be the case with some hardware that raises the interrupt
• • only some time after the start of vblank.
• • Returns:
• • Zero on success or a negative error code on failure.
• */

+int drm_crtc_vblank_get_accurate(struct drm_crtc *crtc) +{

• return drm_vblank_get(crtc->dev, drm_crtc_index(crtc), true);

+} +EXPORT_SYMBOL(drm_crtc_vblank_get_accurate);

static void drm_vblank_put(struct drm_device *dev, unsigned int pipe) { struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; @@ -1053,7 +1080,7 @@ void drm_wait_one_vblank(struct drm_device *dev, unsigned int pipe) if (WARN_ON(pipe >= dev->num_crtcs)) return;

• ret = drm_vblank_get(dev, pipe);

• ret = drm_vblank_get(dev, pipe, true); if (WARN(ret, "vblank not available on crtc %i, ret=%i\n", pipe, ret)) return;

@@ -1248,7 +1275,7 @@ static void drm_legacy_vblank_pre_modeset(struct drm_device *dev, */ if (!vblank->inmodeset) { vblank->inmodeset = 0x1;

• if (drm_vblank_get(dev, pipe) == 0)
  

• if (drm_vblank_get(dev, pipe, false) == 0)
  vblank->inmodeset |= 0x2;
  

  }

} @@ -1448,7 +1475,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data, return 0; }

• ret = drm_vblank_get(dev, pipe);

• ret = drm_vblank_get(dev, pipe, false); if (ret) { DRM_DEBUG("crtc %d failed to acquire vblank counter, %d\n", pipe, ret); return ret;

diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index 7fba9efe4951..5629e7841318 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -162,6 +162,7 @@ void drm_crtc_arm_vblank_event(struct drm_crtc *crtc, bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe); bool drm_crtc_handle_vblank(struct drm_crtc *crtc); int drm_crtc_vblank_get(struct drm_crtc *crtc); +int drm_crtc_vblank_get_accurate(struct drm_crtc *crtc); void drm_crtc_vblank_put(struct drm_crtc *crtc); void drm_wait_one_vblank(struct drm_device *dev, unsigned int pipe); void drm_crtc_wait_one_vblank(struct drm_crtc *crtc); -- 2.13.0