On 02/09/2016 10:54 AM, Daniel Vetter wrote:
On Mon, Feb 08, 2016 at 02:13:24AM +0100, Mario Kleiner wrote:
Otherwise if a kms driver calls into drm_vblank_off() more than once before calling drm_vblank_on() again, the redundant calls to vblank_disable_and_save() will call drm_update_vblank_count() while hw vblank counters and vblank timestamping are in a undefined state during modesets, dpms off etc.
At least with the legacy drm helpers it is not unusual to get multiple calls to drm_vblank_off and drm_vblank_on, e.g., half a dozen calls to drm_vblank_off and two calls to drm_vblank_on were observed on radeon-kms during dpms-off -> dpms-on transition.
Fixes large jumps of the software maintained vblank counter due to the hardware vblank counter resetting to zero during dpms off or modeset, e.g., if radeon-kms is modified to use drm_vblank_off/on instead of drm_vblank_pre/post_modeset().
This fixes a regression caused by the changes made to drm_update_vblank_count() in Linux 4.4.
Signed-off-by: Mario Kleiner mario.kleiner.de@gmail.com Cc: stable@vger.kernel.org # 4.4+ Cc: michel@daenzer.net Cc: vbabka@suse.cz Cc: ville.syrjala@linux.intel.com Cc: daniel.vetter@ffwll.ch Cc: dri-devel@lists.freedesktop.org Cc: alexander.deucher@amd.com Cc: christian.koenig@amd.com
drivers/gpu/drm/drm_irq.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 607f493..bcb8528 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1313,7 +1313,13 @@ void drm_vblank_off(struct drm_device *dev, unsigned int pipe) spin_lock_irqsave(&dev->event_lock, irqflags);
spin_lock(&dev->vbl_lock);
- vblank_disable_and_save(dev, pipe);
- DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n",
pipe, vblank->enabled, vblank->inmodeset);- /* Avoid redundant vblank disables without previous drm_vblank_on(). */
- if (!vblank->inmodeset)
Since atomic drivers shouldn't suck so badly at this, maybe
if (DRIVER_ATOMIC || !vblank->inmodeset)
instead? That way the flexibility would be constraint to old drivers that need it because legacy crtc helpers suck. With that change:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Ok, thanks, will change that. -mario
vblank_disable_and_save(dev, pipe);wake_up(&vblank->queue);
/*
@@ -1415,6 +1421,9 @@ void drm_vblank_on(struct drm_device *dev, unsigned int pipe) return;
spin_lock_irqsave(&dev->vbl_lock, irqflags);
- DRM_DEBUG_VBL("crtc %d, vblank enabled %d, inmodeset %d\n",
pipe, vblank->enabled, vblank->inmodeset);- /* Drop our private "prevent drm_vblank_get" refcount */ if (vblank->inmodeset) { atomic_dec(&vblank->refcount);
-- 1.9.1