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Date:   Fri, 3 May 2019 09:51:30 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Sean Paul <sean@...rly.run>
Cc:     dri-devel@...ts.freedesktop.org, Sean Paul <seanpaul@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/10] drm: Add atomic variants of enable/disable to
 encoder helper funcs

On Thu, May 02, 2019 at 03:49:43PM -0400, Sean Paul wrote:
> From: Sean Paul <seanpaul@...omium.org>
> 
> 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
> 
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Signed-off-by: Sean Paul <seanpaul@...omium.org>
> ---
>  drivers/gpu/drm/drm_atomic_helper.c      |  6 +++-
>  include/drm/drm_modeset_helper_vtables.h | 45 ++++++++++++++++++++++++
>  2 files changed, 50 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 553415fe8ede..71cc7d6b0644 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1001,6 +1001,8 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
>  		if (funcs) {
>  			if (new_conn_state->crtc && funcs->prepare)
>  				funcs->prepare(encoder);
> +			else if (funcs->atomic_disable)
> +				funcs->atomic_disable(encoder, old_state);

I'd put the atomic one first. The reason why ->disable here is later is
that ->disable has some really funky meaning in the old legacy crtc
helpers, and hence ->prepare was preferrable: Legacy ->disable also was
supposed to release resources (something we now do in
->atomic_destroy_state). See the huge NOTE: in the @disable kerneldoc.


>  			else if (funcs->disable)
>  				funcs->disable(encoder);
>  			else if (funcs->dpms)
> @@ -1309,7 +1311,9 @@ 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);
> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> index 8f3602811eb5..de57fb40cb6e 100644
> --- a/include/drm/drm_modeset_helper_vtables.h
> +++ b/include/drm/drm_modeset_helper_vtables.h
> @@ -675,6 +675,51 @@ 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. It takes priority over @disable during atomic commits.
> +	 *
> +	 * This hook is used only 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.
> +	 */

I'd add something like "For atomic drivers also consider @atomic_disable"
to the kerneldoc of @disable (before the NOTE: which is only relevant for
pre-atomic). Same for the enable side.

> +	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. It is called in place of @enable during atomic
> +	 * commits.

needs to be adjusted here for "takes priority".
> +	 *
> +	 * This hook is used only by atomic helpers, for symmetry with @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 (using either DPMS or the new "ACTIVE" property) works
> +	 * @enable must be the inverse of @disable for atomic drivers.
> +	 */
> +	void (*atomic_enable)(struct drm_encoder *encoder,
> +			      struct drm_atomic_state *state);
> +

With the nits:

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

>  	/**
>  	 * @disable:
>  	 *
> -- 
> Sean Paul, Software Engineer, Google / Chromium OS
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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