Re: [PATCH v6 3/5] drm: Document variable refresh properties
On Wed, 7 Nov 2018 15:10:31 + "Kazlauskas, Nicholas" wrote: > On 11/7/18 9:57 AM, Wentland, Harry wrote: > > > > > > 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 > >> Cc: Harry Wentland > >> Cc: Manasi Navare > >> Cc: Pekka Paalanen > >> Cc: Ville Syrjälä > >> Cc: Michel Dänzer > >> --- > >> 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 _connector and _crtc objects. > >> + * > >> + * "vrr_capable": > >> + *Optional _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 _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 _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
Re: [PATCH v6 3/5] drm: Document variable refresh properties
On 11/7/18 9:57 AM, Wentland, Harry wrote: > > > 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 >> Cc: Harry Wentland >> Cc: Manasi Navare >> Cc: Pekka Paalanen >> Cc: Ville Syrjälä >> Cc: Michel Dänzer >> --- >> 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 _connector and _crtc objects. >> + * >> + * "vrr_capable": >> + * Optional _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 _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 _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. Good point about mentioning that userspace shouldn't expect this to work well with frequent (and large) changes in vertical front porch duration. I should probably more clearly word that the panel brightness may differ based on the vertical front porch duration. So large changes will
Re: [PATCH v6 3/5] drm: Document variable refresh properties
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 > Cc: Harry Wentland > Cc: Manasi Navare > Cc: Pekka Paalanen > Cc: Ville Syrjälä > Cc: Michel Dänzer > --- > 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 _connector and _crtc objects. > + * > + * "vrr_capable": > + * Optional _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 _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 _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 >
[PATCH v6 3/5] drm: Document variable refresh properties
These include the drm_connector 'vrr_capable' and the drm_crtc 'vrr_enabled' properties. Signed-off-by: Nicholas Kazlauskas Cc: Harry Wentland Cc: Manasi Navare Cc: Pekka Paalanen Cc: Ville Syrjälä Cc: Michel Dänzer --- 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 + * 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 _connector and _crtc objects. + * + * "vrr_capable": + * Optional _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 _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 _connector object. The + * veritcal front porch duration will be extended until page-flip or + * 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. + * + * 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 -- 2.19.1 ___ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
