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@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # 4.4+ > Cc: michel@xxxxxxxxxxx > Cc: vbabka@xxxxxxx > Cc: ville.syrjala@xxxxxxxxxxxxxxx > Cc: daniel.vetter@xxxxxxxx > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx > Cc: alexander.deucher@xxxxxxx > Cc: christian.koenig@xxxxxxx > --- > 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@xxxxxxxx> > + 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 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html