drm: Add atomic variants of enable/disable to encoder helper funcs

This patch adds atomic_enable and atomic_disable callbacks to the
encoder helpers. This will allow encoders to make informed decisions in
their start-up/shutdown based on the committed state.

Aside from the new hooks, this patch also introduces the new signature
for .atomic_* functions going forward. Instead of passing object state
(well, encoders don't have atomic state, but let's ignore that), we pass
the entire atomic state so the driver can inspect more than what's
happening locally.

This is particularly important for the upcoming self refresh helpers.

Changes in v3:
- Added patch to the set
Changes in v4:
- Move atomic_disable above prepare (Daniel)
- Add breadcrumb to .enable() docbook (Daniel)
Changes in v5:
- None
Changes in v6:
- Tweak kerneldoc some more (Sam)

Link to v3: https://patchwork.freedesktop.org/patch/msgid/20190502194956.218441-2-sean@poorly.run
Link to v4: https://patchwork.freedesktop.org/patch/msgid/20190508160920.144739-2-sean@poorly.run
Link to v5: https://patchwork.freedesktop.org/patch/msgid/20190611160844.257498-2-sean@poorly.run

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190611204959.180855-1-sean@poorly.run

drivers/gpu/drm/drm_atomic_helper.c

@@ -1002,7 +1002,9 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 
 		/* Right function depends upon target state. */
 		if (funcs) {
-			if (new_conn_state->crtc && funcs->prepare)
+			if (funcs->atomic_disable)
+				funcs->atomic_disable(encoder, old_state);
+			else if (new_conn_state->crtc && funcs->prepare)
 				funcs->prepare(encoder);
 			else if (funcs->disable)
 				funcs->disable(encoder);
@@ -1311,7 +1313,9 @@ void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
 		drm_bridge_pre_enable(encoder->bridge);
 
 		if (funcs) {
-			if (funcs->enable)
+			if (funcs->atomic_enable)
+				funcs->atomic_enable(encoder, old_state);
+			else if (funcs->enable)
 				funcs->enable(encoder);
 			else if (funcs->commit)
 				funcs->commit(encoder);

include/drm/drm_modeset_helper_vtables.h

@@ -679,6 +679,52 @@ struct drm_encoder_helper_funcs {
 	enum drm_connector_status (*detect)(struct drm_encoder *encoder,
 					    struct drm_connector *connector);
 
+	/**
+	 * @atomic_disable:
+	 *
+	 * This callback should be used to disable the encoder. With the atomic
+	 * drivers it is called before this encoder's CRTC has been shut off
+	 * using their own &drm_crtc_helper_funcs.atomic_disable hook. If that
+	 * sequence is too simple drivers can just add their own driver private
+	 * encoder hooks and call them from CRTC's callback by looping over all
+	 * encoders connected to it using for_each_encoder_on_crtc().
+	 *
+	 * This callback is a variant of @disable that provides the atomic state
+	 * to the driver. If @atomic_disable is implemented, @disable is not
+	 * called by the helpers.
+	 *
+	 * This hook is only used by atomic helpers. Atomic drivers don't need
+	 * to implement it if there's no need to disable anything at the encoder
+	 * level. To ensure that runtime PM handling (using either DPMS or the
+	 * new "ACTIVE" property) works @atomic_disable must be the inverse of
+	 * @atomic_enable.
+	 */
+	void (*atomic_disable)(struct drm_encoder *encoder,
+			       struct drm_atomic_state *state);
+
+	/**
+	 * @atomic_enable:
+	 *
+	 * This callback should be used to enable the encoder. It is called
+	 * after this encoder's CRTC has been enabled using their own
+	 * &drm_crtc_helper_funcs.atomic_enable hook. If that sequence is
+	 * too simple drivers can just add their own driver private encoder
+	 * hooks and call them from CRTC's callback by looping over all encoders
+	 * connected to it using for_each_encoder_on_crtc().
+	 *
+	 * This callback is a variant of @enable that provides the atomic state
+	 * to the driver. If @atomic_enable is implemented, @enable is not
+	 * called by the helpers.
+	 *
+	 * This hook is only used by atomic helpers, it is the opposite of
+	 * @atomic_disable. Atomic drivers don't need to implement it if there's
+	 * no need to enable anything at the encoder level. To ensure that
+	 * runtime PM handling works @atomic_enable must be the inverse of
+	 * @atomic_disable.
+	 */
+	void (*atomic_enable)(struct drm_encoder *encoder,
+			      struct drm_atomic_state *state);
+
 	/**
 	 * @disable:
 	 *
@@ -695,6 +741,9 @@ struct drm_encoder_helper_funcs {
 	 * handling (using either DPMS or the new "ACTIVE" property) works
 	 * @disable must be the inverse of @enable for atomic drivers.
 	 *
+	 * For atomic drivers also consider @atomic_disable and save yourself
+	 * from having to read the NOTE below!
+	 *
 	 * NOTE:
 	 *
 	 * With legacy CRTC helpers there's a big semantic difference between