Message-ID: <931a519e-605e-4f53-9a03-43b8d53ed987@ideasonboard.com>
Date: Thu, 3 Apr 2025 12:49:20 +0300
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Aradhya Bhatia <aradhya.bhatia@...ux.dev>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: Nishanth Menon <nm@...com>, Vignesh Raghavendra <vigneshr@...com>,
 Devarsh Thakkar <devarsht@...com>, Praneeth Bajjuri <praneeth@...com>,
 Udit Kumar <u-kumar1@...com>, Jayesh Choudhary <j-choudhary@...com>,
 Alexander Sverdlin <alexander.sverdlin@...mens.com>,
 Dominik Haller <d.haller@...tec.de>,
 DRI Development List <dri-devel@...ts.freedesktop.org>,
 Linux Kernel List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 13/14] drm/bridge: Update the bridge enable/disable
 doc

Hi,

On 29/03/2025 13:53, Aradhya Bhatia wrote:
> Now that the bridges get pre-enabled before the CRTC is enabled, and get
> post-disabled after the CRTC is disabled, update the function
> descriptions to accurately reflect the updated scenario.
> 
> The enable sequence for the display pipeline looks 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 looks like:
> 
> 	bridge[n]_disable
> 	...
> 	bridge[1]_disable
> 
> 	encoder_disable
> 	crtc_disable
> 
> 	bridge[1]_post_disable
> 	...
> 	bridge[n]_post_disable
> 
> Signed-off-by: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
> ---
>   include/drm/drm_bridge.h | 216 +++++++++++++++++++++++++++------------
>   1 file changed, 150 insertions(+), 66 deletions(-)
> 
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index cdad3b78a195..fc126562733c 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -164,17 +164,28 @@ 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.
>   	 *
> +	 * It is called right before the preceding element in the display pipe
> +	 * is disabled. If the preceding element is a &drm_bridge, then it's
> +	 * called before that bridge is disabled.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right before the encoder and the CRTC are disabled via the
> +	 * following hooks.
> +	 * &drm_encoder_helper_funcs.atomic_disable, or
> +	 * &drm_encoder_helper_funcs.prepare, or
> +	 * &drm_encoder_helper_funcs.disable, or &drm_encoder_helper_funcs.dpms
> +	 * hook for the encoder, and
> +	 * &drm_crtc_helper_funcs.prepare, or
> +	 * &drm_crtc_helper_funcs.atomic_disable, or
> +	 * &drm_crtc_helper_funcs.disable, or &drm_crtc_helper_funcs.dpms hook
> +	 * for the CRTC.
> +	 *

This is quite difficult to read. Maybe something like:

It is called right before the preceding element in the display pipe is
disabled.

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 right 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 are disabled via one of:

- &drm_crtc_helper_funcs.atomic_disable
- &drm_crtc_helper_funcs.prepare
- &drm_crtc_helper_funcs.disable
- &drm_crtc_helper_funcs.dpms hook

  Tomi

>   	 * The @disable callback is optional.
>   	 *
>   	 * NOTE:
> @@ -187,17 +198,30 @@ 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.
> +	 *
> +	 * It is called right after the preceding element is post-disabled, and
> +	 * right before the following element gets post-disabled (given that the
> +	 * preceding and following elements are &drm_bridges), unless marked
> +	 * otherwise by the @pre_enable_prev_first flag.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right after the encoder and the CRTC are disabled via the
> +	 * following hooks.
> +	 * &drm_encoder_helper_funcs.atomic_disable, or
> +	 * &drm_encoder_helper_funcs.prepare, or
> +	 * &drm_encoder_helper_funcs.disable, or &drm_encoder_helper_funcs.dpms
> +	 * hook for the encoder, and
> +	 * &drm_crtc_helper_funcs.prepare, or
> +	 * &drm_crtc_helper_funcs.atomic_disable, or
> +	 * &drm_crtc_helper_funcs.disable, or &drm_crtc_helper_funcs.dpms hook
> +	 * for the CRTC.
>   	 *
>   	 * The @post_disable callback is optional.
>   	 *
> @@ -240,18 +264,26 @@ 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.
> +	 *
> +	 * It is called right after the following element is pre-enabled, and
> +	 * right before the preceding element gets pre-enabled (given that the
> +	 * following and preceding elements are &drm_bridges), unless marked
> +	 * otherwise by @pre_enable_prev_first flag.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right before the CRTC and the encoder are enabled via these
> +	 * hooks.
> +	 * &drm_crtc_helper_funcs.atomic_enable, or
> +	 * &drm_crtc_helper_funcs.commit hook for the CRTC, and
> +	 * &drm_encoder_helper_funcs.atomic_enable, or
> +	 * &drm_encoder_helper_funcs.enable, or &drm_encoder_helper_funcs.commit
> +	 * hook for the encoder.
>   	 *
>   	 * The @pre_enable callback is optional.
>   	 *
> @@ -265,19 +297,27 @@ 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.
>   	 *
> +	 * It is called right after the preceding element in the display pipe is
> +	 * enabled. If the preceding element is a &drm_bridge, then it's called
> +	 * after that bridge is enabled.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right after the CRTC and the encoder are enabled via these
> +	 * hooks.
> +	 * &drm_crtc_helper_funcs.atomic_enable, or
> +	 * &drm_crtc_helper_funcs.commit hook for the CRTC, and
> +	 * &drm_encoder_helper_funcs.atomic_enable, or
> +	 * &drm_encoder_helper_funcs.enable, or &drm_encoder_helper_funcs.commit
> +	 * hook for the encoder.
> +	 *
>   	 * The @enable callback is optional.
>   	 *
>   	 * NOTE:
> @@ -290,17 +330,26 @@ 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.
> +	 *
> +	 * It is called right after the following element is pre-enabled, and
> +	 * right before the preceding element gets pre-enabled (given that the
> +	 * following and preceding elements are &drm_bridges), unless marked
> +	 * otherwise by @pre_enable_prev_first flag.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right before the CRTC and the encoder are enabled via these
> +	 * hooks.
> +	 * &drm_crtc_helper_funcs.atomic_enable, or
> +	 * &drm_crtc_helper_funcs.commit hook for the CRTC, and
> +	 * &drm_encoder_helper_funcs.atomic_enable, or
> +	 * &drm_encoder_helper_funcs.enable, or &drm_encoder_helper_funcs.commit
> +	 * hook for the encoder.
>   	 *
>   	 * The @atomic_pre_enable callback is optional.
>   	 */
> @@ -310,18 +359,27 @@ 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.
>   	 *
> +	 * It is called right after the preceding element in the display pipe is
> +	 * enabled. If the preceding element is a &drm_bridge, then it's called
> +	 * after that bridge is enabled.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right after the CRTC and the encoder are enabled via these
> +	 * hooks.
> +	 * &drm_crtc_helper_funcs.atomic_enable, or
> +	 * &drm_crtc_helper_funcs.commit hook for the CRTC, and
> +	 * &drm_encoder_helper_funcs.atomic_enable, or
> +	 * &drm_encoder_helper_funcs.enable, or &drm_encoder_helper_funcs.commit
> +	 * hook for the encoder.
> +	 *
>   	 * The @atomic_enable callback is optional.
>   	 */
>   	void (*atomic_enable)(struct drm_bridge *bridge,
> @@ -329,16 +387,28 @@ 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.
>   	 *
> +	 * It is called right before the preceding element in the display pipe
> +	 * is disabled. If the preceding element is a &drm_bridge, then it's
> +	 * called before that bridge is disabled.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right before the encoder and the CRTC are disabled via the
> +	 * following hooks.
> +	 * &drm_encoder_helper_funcs.atomic_disable, or
> +	 * &drm_encoder_helper_funcs.prepare, or
> +	 * &drm_encoder_helper_funcs.disable, or &drm_encoder_helper_funcs.dpms
> +	 * hook for the encoder, and
> +	 * &drm_crtc_helper_funcs.prepare, or
> +	 * &drm_crtc_helper_funcs.atomic_disable, or
> +	 * &drm_crtc_helper_funcs.disable, or &drm_crtc_helper_funcs.dpms hook
> +	 * for the CRTC.
> +	 *
>   	 * The @atomic_disable callback is optional.
>   	 */
>   	void (*atomic_disable)(struct drm_bridge *bridge,
> @@ -347,16 +417,30 @@ 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.
> +	 *
> +	 * It is called right after the preceding element is post-disabled, and
> +	 * right before the following element gets post-disabled (given that the
> +	 * preceding and following elements are &drm_bridges), unless marked
> +	 * otherwise by the @pre_enable_prev_first flag.
> +	 *
> +	 * If the preceding element of the bridge is a display controller, which
> +	 * has under it a &drm_crtc and a &drm_encoder, then this callback is
> +	 * called right after the encoder and the CRTC are disabled via the
> +	 * following hooks.
> +	 * &drm_encoder_helper_funcs.atomic_disable, or
> +	 * &drm_encoder_helper_funcs.prepare, or
> +	 * &drm_encoder_helper_funcs.disable, or &drm_encoder_helper_funcs.dpms
> +	 * hook for the encoder, and
> +	 * &drm_crtc_helper_funcs.prepare, or
> +	 * &drm_crtc_helper_funcs.atomic_disable, or
> +	 * &drm_crtc_helper_funcs.disable, or &drm_crtc_helper_funcs.dpms hook
> +	 * for the CRTC.
>   	 *
>   	 * The @atomic_post_disable callback is optional.
>   	 */

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