| Message ID | 20210209101523.2954281-1-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/vblank: Document drm_crtc_vblank_restore constraints | expand |
On Tue, Feb 09, 2021 at 11:15:23AM +0100, Daniel Vetter wrote: > I got real badly confused when trying to review a fix from Ville for > this. Let's try to document better what's required for this, and check > the minimal settings at runtime - we can't check ofc that there's > indeed no races in the driver callback. > > Also noticed that the drm_vblank_restore version is unused, so lets > unexport that while at it. > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > --- > drivers/gpu/drm/drm_vblank.c | 25 ++++++++++--------------- > include/drm/drm_vblank.h | 1 - > 2 files changed, 10 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > index c914b14cfb43..05f4d4c078fd 100644 > --- a/drivers/gpu/drm/drm_vblank.c > +++ b/drivers/gpu/drm/drm_vblank.c > @@ -1471,20 +1471,7 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc) > } > EXPORT_SYMBOL(drm_crtc_vblank_on); > > -/** > - * drm_vblank_restore - estimate missed vblanks and update vblank count. > - * @dev: DRM device > - * @pipe: CRTC index > - * > - * Power manamement features can cause frame counter resets between vblank > - * disable and enable. Drivers can use this function in their > - * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since > - * the last &drm_crtc_funcs.disable_vblank using timestamps and update the > - * vblank counter. > - * > - * This function is the legacy version of drm_crtc_vblank_restore(). > - */ > -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) > +static void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) > { > ktime_t t_vblank; > struct drm_vblank_crtc *vblank; > @@ -1520,7 +1507,6 @@ void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) > diff, diff_ns, framedur_ns, cur_vblank - vblank->last); > store_vblank(dev, pipe, diff, t_vblank, cur_vblank); > } > -EXPORT_SYMBOL(drm_vblank_restore); > > /** > * drm_crtc_vblank_restore - estimate missed vblanks and update vblank count. > @@ -1531,9 +1517,18 @@ EXPORT_SYMBOL(drm_vblank_restore); > * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since > * the last &drm_crtc_funcs.disable_vblank using timestamps and update the > * vblank counter. > + * > + * Note that drivers must have race-free high-precision timestamping support, > + * i.e. &drm_crtc_funcs.get_vblank_timestamp must be hooked up and > + * &drm_driver.vblank_disable_immediate must be set to indicate the > + * time-stamping functions are race-free against vblank hardware counter > + * increments. Looks good. Might prevent someone from shooting themselves in the foot. Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > */ > void drm_crtc_vblank_restore(struct drm_crtc *crtc) > { > + WARN_ON_ONCE(!crtc->funcs->get_vblank_timestamp); > + WARN_ON_ONCE(!crtc->dev->vblank_disable_immediate); > + > drm_vblank_restore(crtc->dev, drm_crtc_index(crtc)); > } > EXPORT_SYMBOL(drm_crtc_vblank_restore); > diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h > index dd125f8c766c..733a3e2d1d10 100644 > --- a/include/drm/drm_vblank.h > +++ b/include/drm/drm_vblank.h > @@ -247,7 +247,6 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc); > void drm_crtc_vblank_reset(struct drm_crtc *crtc); > void drm_crtc_vblank_on(struct drm_crtc *crtc); > u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc); > -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe); > void drm_crtc_vblank_restore(struct drm_crtc *crtc); > > void drm_calc_timestamping_constants(struct drm_crtc *crtc, > -- > 2.30.0
On Tue, Feb 09, 2021 at 05:36:07PM +0200, Ville Syrjälä wrote: > On Tue, Feb 09, 2021 at 11:15:23AM +0100, Daniel Vetter wrote: > > I got real badly confused when trying to review a fix from Ville for > > this. Let's try to document better what's required for this, and check > > the minimal settings at runtime - we can't check ofc that there's > > indeed no races in the driver callback. > > > > Also noticed that the drm_vblank_restore version is unused, so lets > > unexport that while at it. > > > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > > --- > > drivers/gpu/drm/drm_vblank.c | 25 ++++++++++--------------- > > include/drm/drm_vblank.h | 1 - > > 2 files changed, 10 insertions(+), 16 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > > index c914b14cfb43..05f4d4c078fd 100644 > > --- a/drivers/gpu/drm/drm_vblank.c > > +++ b/drivers/gpu/drm/drm_vblank.c > > @@ -1471,20 +1471,7 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc) > > } > > EXPORT_SYMBOL(drm_crtc_vblank_on); > > > > -/** > > - * drm_vblank_restore - estimate missed vblanks and update vblank count. > > - * @dev: DRM device > > - * @pipe: CRTC index > > - * > > - * Power manamement features can cause frame counter resets between vblank > > - * disable and enable. Drivers can use this function in their > > - * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since > > - * the last &drm_crtc_funcs.disable_vblank using timestamps and update the > > - * vblank counter. > > - * > > - * This function is the legacy version of drm_crtc_vblank_restore(). > > - */ > > -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) > > +static void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) > > { > > ktime_t t_vblank; > > struct drm_vblank_crtc *vblank; > > @@ -1520,7 +1507,6 @@ void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) > > diff, diff_ns, framedur_ns, cur_vblank - vblank->last); > > store_vblank(dev, pipe, diff, t_vblank, cur_vblank); > > } > > -EXPORT_SYMBOL(drm_vblank_restore); > > > > /** > > * drm_crtc_vblank_restore - estimate missed vblanks and update vblank count. > > @@ -1531,9 +1517,18 @@ EXPORT_SYMBOL(drm_vblank_restore); > > * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since > > * the last &drm_crtc_funcs.disable_vblank using timestamps and update the > > * vblank counter. > > + * > > + * Note that drivers must have race-free high-precision timestamping support, > > + * i.e. &drm_crtc_funcs.get_vblank_timestamp must be hooked up and > > + * &drm_driver.vblank_disable_immediate must be set to indicate the > > + * time-stamping functions are race-free against vblank hardware counter > > + * increments. > > Looks good. Might prevent someone from shooting themselves in > the foot. Yeah hopefully, maybe even me :-) > > Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Thanks for your review, I pushed to drm-misc-next. -Daniel > > > */ > > void drm_crtc_vblank_restore(struct drm_crtc *crtc) > > { > > + WARN_ON_ONCE(!crtc->funcs->get_vblank_timestamp); > > + WARN_ON_ONCE(!crtc->dev->vblank_disable_immediate); > > + > > drm_vblank_restore(crtc->dev, drm_crtc_index(crtc)); > > } > > EXPORT_SYMBOL(drm_crtc_vblank_restore); > > diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h > > index dd125f8c766c..733a3e2d1d10 100644 > > --- a/include/drm/drm_vblank.h > > +++ b/include/drm/drm_vblank.h > > @@ -247,7 +247,6 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc); > > void drm_crtc_vblank_reset(struct drm_crtc *crtc); > > void drm_crtc_vblank_on(struct drm_crtc *crtc); > > u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc); > > -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe); > > void drm_crtc_vblank_restore(struct drm_crtc *crtc); > > > > void drm_calc_timestamping_constants(struct drm_crtc *crtc, > > -- > > 2.30.0 > > -- > Ville Syrjälä > Intel
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index c914b14cfb43..05f4d4c078fd 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1471,20 +1471,7 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc) } EXPORT_SYMBOL(drm_crtc_vblank_on); -/** - * drm_vblank_restore - estimate missed vblanks and update vblank count. - * @dev: DRM device - * @pipe: CRTC index - * - * Power manamement features can cause frame counter resets between vblank - * disable and enable. Drivers can use this function in their - * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since - * the last &drm_crtc_funcs.disable_vblank using timestamps and update the - * vblank counter. - * - * This function is the legacy version of drm_crtc_vblank_restore(). - */ -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) +static void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) { ktime_t t_vblank; struct drm_vblank_crtc *vblank; @@ -1520,7 +1507,6 @@ void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) diff, diff_ns, framedur_ns, cur_vblank - vblank->last); store_vblank(dev, pipe, diff, t_vblank, cur_vblank); } -EXPORT_SYMBOL(drm_vblank_restore); /** * drm_crtc_vblank_restore - estimate missed vblanks and update vblank count. @@ -1531,9 +1517,18 @@ EXPORT_SYMBOL(drm_vblank_restore); * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since * the last &drm_crtc_funcs.disable_vblank using timestamps and update the * vblank counter. + * + * Note that drivers must have race-free high-precision timestamping support, + * i.e. &drm_crtc_funcs.get_vblank_timestamp must be hooked up and + * &drm_driver.vblank_disable_immediate must be set to indicate the + * time-stamping functions are race-free against vblank hardware counter + * increments. */ void drm_crtc_vblank_restore(struct drm_crtc *crtc) { + WARN_ON_ONCE(!crtc->funcs->get_vblank_timestamp); + WARN_ON_ONCE(!crtc->dev->vblank_disable_immediate); + drm_vblank_restore(crtc->dev, drm_crtc_index(crtc)); } EXPORT_SYMBOL(drm_crtc_vblank_restore); diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index dd125f8c766c..733a3e2d1d10 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -247,7 +247,6 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc); void drm_crtc_vblank_reset(struct drm_crtc *crtc); void drm_crtc_vblank_on(struct drm_crtc *crtc); u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc); -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe); void drm_crtc_vblank_restore(struct drm_crtc *crtc); void drm_calc_timestamping_constants(struct drm_crtc *crtc,
I got real badly confused when trying to review a fix from Ville for this. Let's try to document better what's required for this, and check the minimal settings at runtime - we can't check ofc that there's indeed no races in the driver callback. Also noticed that the drm_vblank_restore version is unused, so lets unexport that while at it. Cc: Ville Syrjala <ville.syrjala@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> --- drivers/gpu/drm/drm_vblank.c | 25 ++++++++++--------------- include/drm/drm_vblank.h | 1 - 2 files changed, 10 insertions(+), 16 deletions(-)