linux-kernel - Re: [Patch 1/1] drm/atomic: integrate private objects with suspend/resume helpers

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Message-ID: <20190315105057.GU2665@phenom.ffwll.local>
Date:   Fri, 15 Mar 2019 11:50:57 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Benoit Parrot <bparrot@...com>
Cc:     Daniel Vetter <daniel@...ll.ch>, Rob Clark <robdclark@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Jyri Sarha <jsarha@...com>
Subject: Re: [Patch 1/1] drm/atomic: integrate private objects with
 suspend/resume helpers

On Thu, Mar 14, 2019 at 08:44:45AM -0500, Benoit Parrot wrote:
> During a suspend cycle the atomic state is saved to be used during the
> restore cycle.
> 
> However the current state duplication logic does not duplicate private
> objects. This leads to state inconsistencies at resume time.
> 
> With private objects modeset lock now integrated, we can make sure that
> private object state are properly saved and restored.
> 
> Signed-off-by: Benoit Parrot <bparrot@...com>

Why do you need this? We're doing a full atomic_check, and your
atomic_check should be pulling in any private state objects and
recomputing their states. This smells like papering over a driver bug.

The duplicate helpers should only need to duplicate the uapi-relevant
states, i.e. connector/crtc/planes.
-Daniel

> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 540a77a2ade9..b108021cc092 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3189,6 +3189,7 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
>  	struct drm_connector_list_iter conn_iter;
>  	struct drm_plane *plane;
>  	struct drm_crtc *crtc;
> +	struct drm_private_obj *privobj;
>  	int err = 0;
>  
>  	state = drm_atomic_state_alloc(dev);
> @@ -3218,6 +3219,16 @@ drm_atomic_helper_duplicate_state(struct drm_device *dev,
>  		}
>  	}
>  
> +	drm_for_each_privobj(privobj, dev) {
> +		struct drm_private_state *priv_state;
> +
> +		priv_state = drm_atomic_get_private_obj_state(state, privobj);
> +		if (IS_ERR(priv_state)) {
> +			err = PTR_ERR(priv_state);
> +			goto free;
> +		}
> +	}
> +
>  	drm_connector_list_iter_begin(dev, &conn_iter);
>  	drm_for_each_connector_iter(conn, &conn_iter) {
>  		struct drm_connector_state *conn_state;
> @@ -3325,12 +3336,17 @@ int drm_atomic_helper_commit_duplicated_state(struct drm_atomic_state *state,
>  	struct drm_connector_state *new_conn_state;
>  	struct drm_crtc *crtc;
>  	struct drm_crtc_state *new_crtc_state;
> +	struct drm_private_obj *privobj;
> +	struct drm_private_state *new_priv_state;
>  
>  	state->acquire_ctx = ctx;
>  
>  	for_each_new_plane_in_state(state, plane, new_plane_state, i)
>  		state->planes[i].old_state = plane->state;
>  
> +	for_each_new_private_obj_in_state(state, privobj, new_priv_state, i)
> +		state->private_objs[i].old_state = privobj->state;
> +
>  	for_each_new_crtc_in_state(state, crtc, new_crtc_state, i)
>  		state->crtcs[i].old_state = crtc->state;
>  
> -- 
> 2.17.1
> 

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