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drm: atomic: Clarify documentation around drm_atomic_crtc_needs_modeset 

Add some additional comments to more explicitly describe the meaning and
usage of the three CRTC modeset detection booleans: mode_changed,
connectors_changed and active_changed.

Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Brian Starkey <brian.starkey@arm.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1476352028-16701-1-git-send-email-brian.starkey@arm.com
This commit is contained in:
Brian Starkey 2016-10-13 10:47:08 +01:00 committed by Daniel Vetter
parent f7741aa75e
commit d807ed1c55
3 changed files with 20 additions and 5 deletions
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9
drivers/gpu/drm/drm_atomic_helper.c
View File

@ -458,10 +458,11 @@ mode_fixup(struct drm_atomic_state *state)
* removed from the crtc.
* crtc_state->active_changed is set when crtc_state->active changes,
* which is used for dpms.
* See also: drm_atomic_crtc_needs_modeset()
*
* IMPORTANT:
*
* Drivers which update ->mode_changed (e.g. in their ->atomic_check hooks if a
* Drivers which set ->mode_changed (e.g. in their ->atomic_check hooks if a
* plane update can't be done without a full modeset) _must_ call this function
* afterwards after that change. It is permitted to call this function multiple
* times for the same update, e.g. when the ->atomic_check functions depend upon
@ -510,9 +511,9 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
for_each_connector_in_state(state, connector, connector_state, i) {
/*
* This only sets crtc->mode_changed for routing changes,
* drivers must set crtc->mode_changed themselves when connector
* properties need to be updated.
* This only sets crtc->connectors_changed for routing changes,
* drivers must set crtc->connectors_changed themselves when
* connector properties need to be updated.
*/
ret = update_connector_routing(state, connector,
connector_state);

11
include/drm/drm_atomic.h
View File

@ -365,8 +365,17 @@ int __must_check drm_atomic_nonblocking_commit(struct drm_atomic_state *state);
*
* To give drivers flexibility struct &drm_crtc_state has 3 booleans to track
* whether the state CRTC changed enough to need a full modeset cycle:
* connectors_changed, mode_changed and active_change. This helper simply
* connectors_changed, mode_changed and active_changed. This helper simply
* combines these three to compute the overall need for a modeset for @state.
*
* The atomic helper code sets these booleans, but drivers can and should
* change them appropriately to accurately represent whether a modeset is
* really needed. In general, drivers should avoid full modesets whenever
* possible.
*
* For example if the CRTC mode has changed, and the hardware is able to enact
* the requested mode change without going through a full modeset, the driver
* should clear mode_changed during its ->atomic_check.
*/
static inline bool
drm_atomic_crtc_needs_modeset(struct drm_crtc_state *state)

5
include/drm/drm_crtc.h
View File

@ -116,6 +116,11 @@ struct drm_plane_helper_funcs;
* never return in a failure from the ->atomic_check callback. Userspace assumes
* that a DPMS On will always succeed. In other words: @enable controls resource
* assignment, @active controls the actual hardware state.
*
* The three booleans active_changed, connectors_changed and mode_changed are
* intended to indicate whether a full modeset is needed, rather than strictly
* describing what has changed in a commit.
* See also: drm_atomic_crtc_needs_modeset()
*/
struct drm_crtc_state {
struct drm_crtc *crtc;