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Commit d807ed1c authored by Brian Starkey's avatar Brian Starkey Committed by Daniel Vetter
Browse files

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: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarBrian Starkey <brian.starkey@arm.com>
Acked-by: default avatarAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1476352028-16701-1-git-send-email-brian.starkey@arm.com
parent f7741aa7

drivers/gpu/drm/drm_atomic_helper.c

+5 −4
Original line number Diff line number Diff line
@@ -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);

include/drm/drm_atomic.h

+10 −1
Original line number Diff line number Diff line
@@ -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)

include/drm/drm_crtc.h

+5 −0
Original line number Diff line number Diff line
@@ -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;