[PATCH v13 3/4] drm/atomic-helper: Re-order bridge chain pre-enable and post-disable

[Aradhya Bhatia <aradhya.bhatia@linux.dev>]

From: Aradhya Bhatia <a-bhatia1@ti.com>

Move the bridge pre_enable call before crtc enable, and the bridge
post_disable call after the crtc disable.

The sequence of enable after this patch will look like:

	bridge[n]_pre_enable
	...
	bridge[1]_pre_enable

	crtc_enable
	encoder_enable

	bridge[1]_enable
	...
	bridge[n]_enable

And, the disable sequence for the display pipeline will look like:

	bridge[n]_disable
	...
	bridge[1]_disable

	encoder_disable
	crtc_disable

	bridge[1]_post_disable
	...
	bridge[n]_post_disable

The definition of bridge pre_enable hook says that,
"The display pipe (i.e. clocks and timing signals) feeding this bridge
will not yet be running when this callback is called".

Since CRTC is also a source feeding the bridge, it should not be enabled
before the bridges in the pipeline are pre_enabled. Fix that by
re-ordering the sequence of bridge pre_enable and bridge post_disable.

While at it, update the drm bridge API documentation as well.

Acked-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Tested-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
Signed-off-by: Aradhya Bhatia <aradhya.bhatia@linux.dev>
---
 drivers/gpu/drm/drm_atomic_helper.c |   8 +-
 include/drm/drm_bridge.h            | 249 ++++++++++++++++++++--------
 2 files changed, 187 insertions(+), 70 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 539b7f072c72..2fe6c91910a1 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1336,9 +1336,9 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *state)
 {
 	encoder_bridge_disable(dev, state);
 
-	encoder_bridge_post_disable(dev, state);
-
 	crtc_disable(dev, state);
+
+	encoder_bridge_post_disable(dev, state);
 }
 
 /**
@@ -1674,10 +1674,10 @@ encoder_bridge_enable(struct drm_device *dev, struct drm_atomic_state *state)
 void drm_atomic_helper_commit_modeset_enables(struct drm_device *dev,
 					      struct drm_atomic_state *state)
 {
-	crtc_enable(dev, state);
-
 	encoder_bridge_pre_enable(dev, state);
 
+	crtc_enable(dev, state);
+
 	encoder_bridge_enable(dev, state);
 
 	drm_atomic_helper_commit_writebacks(dev, state);
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 0af5db244db8..ecdeb90e5586 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -165,17 +165,33 @@ struct drm_bridge_funcs {
 	/**
 	 * @disable:
 	 *
-	 * This callback should disable the bridge. It is called right before
-	 * the preceding element in the display pipe is disabled. If the
-	 * preceding element is a bridge this means it's called before that
-	 * bridge's @disable vfunc. If the preceding element is a &drm_encoder
-	 * it's called right before the &drm_encoder_helper_funcs.disable,
-	 * &drm_encoder_helper_funcs.prepare or &drm_encoder_helper_funcs.dpms
-	 * hook.
+	 * The @disable callback should disable the bridge.
 	 *
 	 * The bridge can assume that the display pipe (i.e. clocks and timing
 	 * signals) feeding it is still running when this callback is called.
 	 *
+	 *
+	 * If the preceding element is a &drm_bridge, then this is called before
+	 * that bridge is disabled via one of:
+	 *
+	 * - &drm_bridge_funcs.disable
+	 * - &drm_bridge_funcs.atomic_disable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called before the encoder is disabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_disable
+	 * - &drm_encoder_helper_funcs.prepare
+	 * - &drm_encoder_helper_funcs.disable
+	 * - &drm_encoder_helper_funcs.dpms
+	 *
+	 * and the CRTC is disabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.prepare
+	 * - &drm_crtc_helper_funcs.atomic_disable
+	 * - &drm_crtc_helper_funcs.disable
+	 * - &drm_crtc_helper_funcs.dpms.
+	 *
 	 * The @disable callback is optional.
 	 *
 	 * NOTE:
@@ -188,17 +204,34 @@ struct drm_bridge_funcs {
 	/**
 	 * @post_disable:
 	 *
-	 * This callback should disable the bridge. It is called right after the
-	 * preceding element in the display pipe is disabled. If the preceding
-	 * element is a bridge this means it's called after that bridge's
-	 * @post_disable function. If the preceding element is a &drm_encoder
-	 * it's called right after the encoder's
-	 * &drm_encoder_helper_funcs.disable, &drm_encoder_helper_funcs.prepare
-	 * or &drm_encoder_helper_funcs.dpms hook.
-	 *
 	 * The bridge must assume that the display pipe (i.e. clocks and timing
-	 * signals) feeding it is no longer running when this callback is
-	 * called.
+	 * signals) feeding this bridge is no longer running when the
+	 * @post_disable is called.
+	 *
+	 * This callback should perform all the actions required by the hardware
+	 * after it has stopped receiving signals from the preceding element.
+	 *
+	 * If the preceding element is a &drm_bridge, then this is called after
+	 * that bridge is post-disabled (unless marked otherwise by the
+	 * @pre_enable_prev_first flag) via one of:
+	 *
+	 * - &drm_bridge_funcs.post_disable
+	 * - &drm_bridge_funcs.atomic_post_disable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called after the encoder is disabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_disable
+	 * - &drm_encoder_helper_funcs.prepare
+	 * - &drm_encoder_helper_funcs.disable
+	 * - &drm_encoder_helper_funcs.dpms
+	 *
+	 * and the CRTC is disabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.prepare
+	 * - &drm_crtc_helper_funcs.atomic_disable
+	 * - &drm_crtc_helper_funcs.disable
+	 * - &drm_crtc_helper_funcs.dpms
 	 *
 	 * The @post_disable callback is optional.
 	 *
@@ -241,18 +274,30 @@ struct drm_bridge_funcs {
 	/**
 	 * @pre_enable:
 	 *
-	 * This callback should enable the bridge. It is called right before
-	 * the preceding element in the display pipe is enabled. If the
-	 * preceding element is a bridge this means it's called before that
-	 * bridge's @pre_enable function. If the preceding element is a
-	 * &drm_encoder it's called right before the encoder's
-	 * &drm_encoder_helper_funcs.enable, &drm_encoder_helper_funcs.commit or
-	 * &drm_encoder_helper_funcs.dpms hook.
-	 *
 	 * The display pipe (i.e. clocks and timing signals) feeding this bridge
-	 * will not yet be running when this callback is called. The bridge must
-	 * not enable the display link feeding the next bridge in the chain (if
-	 * there is one) when this callback is called.
+	 * will not yet be running when the @pre_enable is called.
+	 *
+	 * This callback should perform all the necessary actions to prepare the
+	 * bridge to accept signals from the preceding element.
+	 *
+	 * If the preceding element is a &drm_bridge, then this is called before
+	 * that bridge is pre-enabled (unless marked otherwise by
+	 * @pre_enable_prev_first flag) via one of:
+	 *
+	 * - &drm_bridge_funcs.pre_enable
+	 * - &drm_bridge_funcs.atomic_pre_enable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called before the CRTC is enabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.atomic_enable
+	 * - &drm_crtc_helper_funcs.commit
+	 *
+	 * and the encoder is enabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_enable
+	 * - &drm_encoder_helper_funcs.enable
+	 * - &drm_encoder_helper_funcs.commit
 	 *
 	 * The @pre_enable callback is optional.
 	 *
@@ -266,19 +311,31 @@ struct drm_bridge_funcs {
 	/**
 	 * @enable:
 	 *
-	 * This callback should enable the bridge. It is called right after
-	 * the preceding element in the display pipe is enabled. If the
-	 * preceding element is a bridge this means it's called after that
-	 * bridge's @enable function. If the preceding element is a
-	 * &drm_encoder it's called right after the encoder's
-	 * &drm_encoder_helper_funcs.enable, &drm_encoder_helper_funcs.commit or
-	 * &drm_encoder_helper_funcs.dpms hook.
+	 * The @enable callback should enable the bridge.
 	 *
 	 * The bridge can assume that the display pipe (i.e. clocks and timing
 	 * signals) feeding it is running when this callback is called. This
 	 * callback must enable the display link feeding the next bridge in the
 	 * chain if there is one.
 	 *
+	 * If the preceding element is a &drm_bridge, then this is called after
+	 * that bridge is enabled via one of:
+	 *
+	 * - &drm_bridge_funcs.enable
+	 * - &drm_bridge_funcs.atomic_enable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called after the CRTC is enabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.atomic_enable
+	 * - &drm_crtc_helper_funcs.commit
+	 *
+	 * and the encoder is enabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_enable
+	 * - &drm_encoder_helper_funcs.enable
+	 * - drm_encoder_helper_funcs.commit
+	 *
 	 * The @enable callback is optional.
 	 *
 	 * NOTE:
@@ -291,17 +348,30 @@ struct drm_bridge_funcs {
 	/**
 	 * @atomic_pre_enable:
 	 *
-	 * This callback should enable the bridge. It is called right before
-	 * the preceding element in the display pipe is enabled. If the
-	 * preceding element is a bridge this means it's called before that
-	 * bridge's @atomic_pre_enable or @pre_enable function. If the preceding
-	 * element is a &drm_encoder it's called right before the encoder's
-	 * &drm_encoder_helper_funcs.atomic_enable hook.
-	 *
 	 * The display pipe (i.e. clocks and timing signals) feeding this bridge
-	 * will not yet be running when this callback is called. The bridge must
-	 * not enable the display link feeding the next bridge in the chain (if
-	 * there is one) when this callback is called.
+	 * will not yet be running when the @atomic_pre_enable is called.
+	 *
+	 * This callback should perform all the necessary actions to prepare the
+	 * bridge to accept signals from the preceding element.
+	 *
+	 * If the preceding element is a &drm_bridge, then this is called before
+	 * that bridge is pre-enabled (unless marked otherwise by
+	 * @pre_enable_prev_first flag) via one of:
+	 *
+	 * - &drm_bridge_funcs.pre_enable
+	 * - &drm_bridge_funcs.atomic_pre_enable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called before the CRTC is enabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.atomic_enable
+	 * - &drm_crtc_helper_funcs.commit
+	 *
+	 * and the encoder is enabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_enable
+	 * - &drm_encoder_helper_funcs.enable
+	 * - &drm_encoder_helper_funcs.commit
 	 *
 	 * The @atomic_pre_enable callback is optional.
 	 */
@@ -311,18 +381,31 @@ struct drm_bridge_funcs {
 	/**
 	 * @atomic_enable:
 	 *
-	 * This callback should enable the bridge. It is called right after
-	 * the preceding element in the display pipe is enabled. If the
-	 * preceding element is a bridge this means it's called after that
-	 * bridge's @atomic_enable or @enable function. If the preceding element
-	 * is a &drm_encoder it's called right after the encoder's
-	 * &drm_encoder_helper_funcs.atomic_enable hook.
+	 * The @atomic_enable callback should enable the bridge.
 	 *
 	 * The bridge can assume that the display pipe (i.e. clocks and timing
 	 * signals) feeding it is running when this callback is called. This
 	 * callback must enable the display link feeding the next bridge in the
 	 * chain if there is one.
 	 *
+	 * If the preceding element is a &drm_bridge, then this is called after
+	 * that bridge is enabled via one of:
+	 *
+	 * - &drm_bridge_funcs.enable
+	 * - &drm_bridge_funcs.atomic_enable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called after the CRTC is enabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.atomic_enable
+	 * - &drm_crtc_helper_funcs.commit
+	 *
+	 * and the encoder is enabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_enable
+	 * - &drm_encoder_helper_funcs.enable
+	 * - drm_encoder_helper_funcs.commit
+	 *
 	 * The @atomic_enable callback is optional.
 	 */
 	void (*atomic_enable)(struct drm_bridge *bridge,
@@ -330,16 +413,32 @@ struct drm_bridge_funcs {
 	/**
 	 * @atomic_disable:
 	 *
-	 * This callback should disable the bridge. It is called right before
-	 * the preceding element in the display pipe is disabled. If the
-	 * preceding element is a bridge this means it's called before that
-	 * bridge's @atomic_disable or @disable vfunc. If the preceding element
-	 * is a &drm_encoder it's called right before the
-	 * &drm_encoder_helper_funcs.atomic_disable hook.
+	 * The @atomic_disable callback should disable the bridge.
 	 *
 	 * The bridge can assume that the display pipe (i.e. clocks and timing
 	 * signals) feeding it is still running when this callback is called.
 	 *
+	 * If the preceding element is a &drm_bridge, then this is called before
+	 * that bridge is disabled via one of:
+	 *
+	 * - &drm_bridge_funcs.disable
+	 * - &drm_bridge_funcs.atomic_disable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called before the encoder is disabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_disable
+	 * - &drm_encoder_helper_funcs.prepare
+	 * - &drm_encoder_helper_funcs.disable
+	 * - &drm_encoder_helper_funcs.dpms
+	 *
+	 * and the CRTC is disabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.prepare
+	 * - &drm_crtc_helper_funcs.atomic_disable
+	 * - &drm_crtc_helper_funcs.disable
+	 * - &drm_crtc_helper_funcs.dpms.
+	 *
 	 * The @atomic_disable callback is optional.
 	 */
 	void (*atomic_disable)(struct drm_bridge *bridge,
@@ -348,16 +447,34 @@ struct drm_bridge_funcs {
 	/**
 	 * @atomic_post_disable:
 	 *
-	 * This callback should disable the bridge. It is called right after the
-	 * preceding element in the display pipe is disabled. If the preceding
-	 * element is a bridge this means it's called after that bridge's
-	 * @atomic_post_disable or @post_disable function. If the preceding
-	 * element is a &drm_encoder it's called right after the encoder's
-	 * &drm_encoder_helper_funcs.atomic_disable hook.
-	 *
 	 * The bridge must assume that the display pipe (i.e. clocks and timing
-	 * signals) feeding it is no longer running when this callback is
-	 * called.
+	 * signals) feeding this bridge is no longer running when the
+	 * @atomic_post_disable is called.
+	 *
+	 * This callback should perform all the actions required by the hardware
+	 * after it has stopped receiving signals from the preceding element.
+	 *
+	 * If the preceding element is a &drm_bridge, then this is called after
+	 * that bridge is post-disabled (unless marked otherwise by the
+	 * @pre_enable_prev_first flag) via one of:
+	 *
+	 * - &drm_bridge_funcs.post_disable
+	 * - &drm_bridge_funcs.atomic_post_disable
+	 *
+	 * If the preceding element of the bridge is a display controller, then
+	 * this callback is called after the encoder is disabled via one of:
+	 *
+	 * - &drm_encoder_helper_funcs.atomic_disable
+	 * - &drm_encoder_helper_funcs.prepare
+	 * - &drm_encoder_helper_funcs.disable
+	 * - &drm_encoder_helper_funcs.dpms
+	 *
+	 * and the CRTC is disabled via one of:
+	 *
+	 * - &drm_crtc_helper_funcs.prepare
+	 * - &drm_crtc_helper_funcs.atomic_disable
+	 * - &drm_crtc_helper_funcs.disable
+	 * - &drm_crtc_helper_funcs.dpms
 	 *
 	 * The @atomic_post_disable callback is optional.
 	 */
-- 
2.34.1