Re: [Intel-gfx] [PATCH 06/26] drm/atomic: Add __drm_atomic_get_current_plane_state

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 29-05-16 om 20:35 schreef Daniel Vetter:
> ... and use it in msm&vc4. Again just want to encapsulate
> drm_atomic_state internals a bit.
>
> The const threading is a bit awkward in vc4 since C sucks, but I still
> think it's worth to enforce this. Eventually I want to make all the
> obj->state pointers const too, but that's a lot more work ...
>
> Cc: Eric Anholt <eric@anholt.net>
> Cc: Rob Clark <robdclark@gmail.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c | 10 +++------
>  drivers/gpu/drm/vc4/vc4_crtc.c           | 11 +++-------
>  drivers/gpu/drm/vc4/vc4_drv.h            |  2 +-
>  drivers/gpu/drm/vc4/vc4_plane.c          |  5 +++--
>  include/drm/drm_atomic.h                 | 36 ++++++++++++++++++++++++++++++++
>  5 files changed, 46 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
> index 88fe256c1931..6d4086ee0503 100644
> --- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
> +++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
> @@ -383,19 +383,15 @@ static int mdp5_crtc_atomic_check(struct drm_crtc *crtc,
>  	 */
>  	hw_cfg = mdp5_cfg_get_hw_config(mdp5_kms->cfg);
>  	drm_atomic_crtc_state_for_each_plane(plane, state) {
> -		struct drm_plane_state *pstate;
> +		const struct drm_plane_state *pstate;
>  		if (cnt >= (hw_cfg->lm.nb_stages)) {
>  			dev_err(dev->dev, "too many planes!\n");
>  			return -EINVAL;
>  		}
>  
> -		pstate = state->state->plane_states[drm_plane_index(plane)];
> +		pstate = __drm_atomic_get_current_plane_state(state->state,
> +							      plane);
>  
> -		/* plane might not have changed, in which case take
> -		 * current state:
> -		 */
> -		if (!pstate)
> -			pstate = plane->state;
>  		pstates[cnt].plane = plane;
>  		pstates[cnt].state = to_mdp5_plane_state(pstate);
>  
> diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
> index 904d0754ad78..703bda170105 100644
> --- a/drivers/gpu/drm/vc4/vc4_crtc.c
> +++ b/drivers/gpu/drm/vc4/vc4_crtc.c
> @@ -405,14 +405,9 @@ static int vc4_crtc_atomic_check(struct drm_crtc *crtc,
>  		return -EINVAL;
>  
>  	drm_atomic_crtc_state_for_each_plane(plane, state) {
> -		struct drm_plane_state *plane_state =
> -			state->state->plane_states[drm_plane_index(plane)];
> -
> -		/* plane might not have changed, in which case take
> -		 * current state:
> -		 */
> -		if (!plane_state)
> -			plane_state = plane->state;
> +		const struct drm_plane_state *plane_state =
> +			__drm_atomic_get_current_plane_state(state->state,
> +							     plane);
>  
>  		dlist_count += vc4_plane_dlist_size(plane_state);
>  	}
> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
> index 37cac59401d7..c799baabc008 100644
> --- a/drivers/gpu/drm/vc4/vc4_drv.h
> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
> @@ -469,7 +469,7 @@ int vc4_kms_load(struct drm_device *dev);
>  struct drm_plane *vc4_plane_init(struct drm_device *dev,
>  				 enum drm_plane_type type);
>  u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist);
> -u32 vc4_plane_dlist_size(struct drm_plane_state *state);
> +u32 vc4_plane_dlist_size(const struct drm_plane_state *state);
>  void vc4_plane_async_set_fb(struct drm_plane *plane,
>  			    struct drm_framebuffer *fb);
>  
> diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
> index 4037b52fde31..5d2c3d9fd17a 100644
> --- a/drivers/gpu/drm/vc4/vc4_plane.c
> +++ b/drivers/gpu/drm/vc4/vc4_plane.c
> @@ -690,9 +690,10 @@ u32 vc4_plane_write_dlist(struct drm_plane *plane, u32 __iomem *dlist)
>  	return vc4_state->dlist_count;
>  }
>  
> -u32 vc4_plane_dlist_size(struct drm_plane_state *state)
> +u32 vc4_plane_dlist_size(const struct drm_plane_state *state)
>  {
> -	struct vc4_plane_state *vc4_state = to_vc4_plane_state(state);
> +	const struct vc4_plane_state *vc4_state =
> +		container_of(state, typeof(*vc4_state), base);
>  
>  	return vc4_state->dlist_count;
>  }
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 92c84e9ab09a..4e97186293be 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -109,6 +109,42 @@ drm_atomic_get_existing_connector_state(struct drm_atomic_state *state,
>  	return state->connector_states[index];
>  }
>  
> +/**
> + * __drm_atomic_get_current_plane_state - get current plane state
> + * @state: global atomic state object
> + * @plane: plane to grab
> + *
> + * This function returns the plane state for the given plane, either from
> + * @state, or if the plane isn't part of the atomic state update, from @plane.
> + * This is useful in atomic check callbacks, when drivers need to peek at, but
> + * not change, state of other planes, since it avoids threading an error code
> + * back up the call chain.
> + *
> + * WARNING:
> + *
> + * Note that this function is in general unsafe since it doesn't check for the
> + * required locking for access state structures. Drivers must ensure that it is
> + * save to access the returned state structure through other means. One commone
> + * example is when planes are fixed to a single CRTC, and the driver knows that
> + * the CRTC locks is held already. In that case holding the CRTC locks gives a
> + * read-lock on all planes connected to that CRTC. But if planes can be
> + * reassigned things get more tricky. In that case it's better to use
> + * drm_atomic_get_plane_state and wire up full error handling.
> + *
> + * Returns:
> + *
> + * Read-only pointer to the current plane state.
> + */
> +static inline const struct drm_plane_state *
> +__drm_atomic_get_current_plane_state(struct drm_atomic_state *state,
> +				     struct drm_plane *plane)
> +{
> +	if (state->plane_states[drm_plane_index(plane)])
> +		return state->plane_states[drm_plane_index(plane)];
Could use a debug WARN_ON here. Just in case someone tries to use this for a plane that can't be safely checked:

WARN_ON(!plane->state->crtc || !drm_modeset_is_locked(&plane->state->crtc->mutex));

Also use drm_atomic_get_existing_plane_state?

~Maarten
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