On 2018-11-06 3:24 p.m., Nicholas Kazlauskas wrote: > These include the drm_connector 'vrr_capable' and the drm_crtc > 'vrr_enabled' properties. > > Signed-off-by: Nicholas Kazlauskas <nicholas.kazlaus...@amd.com> > Cc: Harry Wentland <harry.wentl...@amd.com> > Cc: Manasi Navare <manasi.d.nav...@intel.com> > Cc: Pekka Paalanen <ppaala...@gmail.com> > Cc: Ville Syrjälä <ville.syrj...@linux.intel.com> > Cc: Michel Dänzer <mic...@daenzer.net> > --- > Documentation/gpu/drm-kms.rst | 7 ++++ > drivers/gpu/drm/drm_connector.c | 61 +++++++++++++++++++++++++++++++++ > 2 files changed, 68 insertions(+) > > diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst > index 4b1501b4835b..8da2a178cf85 100644 > --- a/Documentation/gpu/drm-kms.rst > +++ b/Documentation/gpu/drm-kms.rst > @@ -575,6 +575,13 @@ Explicit Fencing Properties > .. kernel-doc:: drivers/gpu/drm/drm_atomic_uapi.c > :doc: explicit fencing properties > > + > +Variable Refresh Properties > +--------------------------- > + > +.. kernel-doc:: drivers/gpu/drm/drm_connector.c > + :doc: Variable refresh properties > + > Existing KMS Properties > ----------------------- > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > index 49290060ab7b..a6adf5450db3 100644 > --- a/drivers/gpu/drm/drm_connector.c > +++ b/drivers/gpu/drm/drm_connector.c > @@ -1255,6 +1255,67 @@ int drm_mode_create_scaling_mode_property(struct > drm_device *dev) > } > EXPORT_SYMBOL(drm_mode_create_scaling_mode_property); > > +/** > + * DOC: Variable refresh properties > + * > + * Variable refresh rate capable displays can dynamically adjust their > + * refresh rate by extending the duration of their vertical porch until
vertical porch -> vertical front porch > + * page flip or timeout occurs. This can reduce or remove stuttering > + * and latency in scenarios where the page flip does not align with the > + * vblank interval. > + * > + * An example scenario would be an application flipping at a constant rate > + * of 48Hz on a 60Hz display. The page flip will frequently miss the vblank > + * interval and the same contents will be displayed twice. This can be > + * observed as stuttering for content with motion. > + * > + * If variable refresh rate was active on a display that supported a > + * variable refresh range from 35Hz to 60Hz no stuttering would be observable > + * for the example scenario. The minimum supported variable refresh rate of > + * 35Hz is below the page flip frequency and the vertical front porch can > + * be extended until the page flip occurs. The vblank interval will be > + * directly aligned to the page flip rate. > + * > + * Userspace control for variable refresh rate is supported via properties > + * on the &drm_connector and &drm_crtc objects. > + * > + * "vrr_capable": > + * Optional &drm_connector boolean property that drivers should attach > + * with drm_connector_attach_vrr_capable_property() on connectors that > + * could support variable refresh rates. Drivers should update the > + * property value by calling drm_connector_set_vrr_capable_property(). > + * > + * Absence of the property should indicate absence of support. > + * > + * "vrr_enabled": > + * Default &drm_crtc boolean property that notifies the driver that the > + * content on the CRTC is suitable for variable refresh rate presentation. > + * The driver will take this property as a hint to enable variable > + * refresh rate support if the receiver supports it, ie. if the > + * "vrr_capable" property is true on the &drm_connector object. The > + * veritcal front porch duration will be extended until page-flip or veritcal -> vertical > + * timeout when enabled. > + * > + * The minimum vertical front porch duration is defined as the vertical > + * front porch duration for the current mode. > + * > + * The maximum vertical front porch duration is greater than or equal to > + * the minimum vertical front porch duration. The duration is derived > + * from the minimum supported variable refresh rate for the connector. > + * > + * The driver may place further restrictions within these minimum > + * and maximum bounds. > + * > + * Some displays may exhibit noticeable differences in brightness when > + * varying vertical front porch duration. > + * Maybe something like this makes sense here: * Some displays may exhibit noticeable differences in brightness when * varying vertical front porch duration drastically. It is therefore * advised userspace only provide the "vrr_enabled" hint for content * with a render rate that is expected to change gradually frame to frame, * such as games. > + * The semantics for the vertical blank timestamp differ when > + * variable refresh rate is active. The vertical blank timestamp > + * is defined to be an estimate using the current mode's fixed > + * refresh rate timings. The semantics for the page-flip event > + * timestamp remain the same. > + */ > + > /** > * drm_connector_attach_vrr_capable_property - creates the > * vrr_capable property > _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
