Re: [PATCH v3 1/3] drm/atomic: Allow drivers to write their own plane check for async flips

[Pekka Paalanen <pekka.paalanen@haloniitty.fi>]

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On Sun, 28 Jan 2024 18:25:13 -0300
André Almeida <andrealmeid@igalia.com> wrote:

> Some hardware are more flexible on what they can flip asynchronously, so
> rework the plane check so drivers can implement their own check, lifting
> up some of the restrictions.
> 
> Signed-off-by: André Almeida <andrealmeid@igalia.com>
> ---
> v3: no changes
> 
>  drivers/gpu/drm/drm_atomic_uapi.c | 62 ++++++++++++++++++++++---------
>  include/drm/drm_atomic_uapi.h     | 12 ++++++
>  include/drm/drm_plane.h           |  5 +++
>  3 files changed, 62 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index aee4a65d4959..6d5b9fec90c7 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -620,7 +620,7 @@ static int drm_atomic_plane_set_property(struct drm_plane *plane,
>  	return 0;
>  }
>  
> -static int
> +int
>  drm_atomic_plane_get_property(struct drm_plane *plane,
>  		const struct drm_plane_state *state,
>  		struct drm_property *property, uint64_t *val)
> @@ -683,6 +683,7 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL(drm_atomic_plane_get_property);
>  
>  static int drm_atomic_set_writeback_fb_for_connector(
>  		struct drm_connector_state *conn_state,
> @@ -1026,18 +1027,54 @@ int drm_atomic_connector_commit_dpms(struct drm_atomic_state *state,
>  	return ret;
>  }
>  
> -static int drm_atomic_check_prop_changes(int ret, uint64_t old_val, uint64_t prop_value,
> +int drm_atomic_check_prop_changes(int ret, uint64_t old_val, uint64_t prop_value,

Hi,

should the word "async" be somewhere in the function name?

>  					 struct drm_property *prop)
>  {
>  	if (ret != 0 || old_val != prop_value) {
>  		drm_dbg_atomic(prop->dev,
> -			       "[PROP:%d:%s] No prop can be changed during async flip\n",
> +			       "[PROP:%d:%s] This prop cannot be changed during async flip\n",
>  			       prop->base.id, prop->name);
>  		return -EINVAL;
>  	}
>  
>  	return 0;
>  }
> +EXPORT_SYMBOL(drm_atomic_check_prop_changes);
> +
> +/* plane changes may have exceptions, so we have a special function for them */
> +static int drm_atomic_check_plane_changes(struct drm_property *prop,
> +					  struct drm_plane *plane,
> +					  struct drm_plane_state *plane_state,
> +					  struct drm_mode_object *obj,
> +					  u64 prop_value, u64 old_val)
> +{
> +	struct drm_mode_config *config = &plane->dev->mode_config;
> +	int ret;
> +
> +	if (plane->funcs->check_async_props)
> +		return plane->funcs->check_async_props(prop, plane, plane_state,
> +							     obj, prop_value, old_val);

Is it really ok to allow drivers to opt-in to also *reject* the FB_ID
and IN_FENCE_FD props on async commits?

Either intentionally or by accident.

> +
> +	/*
> +	 * if you are trying to change something other than the FB ID, your
> +	 * change will be either rejected or ignored, so we can stop the check
> +	 * here
> +	 */
> +	if (prop != config->prop_fb_id) {
> +		ret = drm_atomic_plane_get_property(plane, plane_state,
> +						    prop, &old_val);
> +		return drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);

When I first read this code, it seemed to say: "If the prop is not
FB_ID, then do the usual prop change checking that happens on all
changes, not only async.". Reading this patch a few more times over, I
finally realized drm_atomic_check_prop_changes() is about async
specifically.

> +	}
> +
> +	if (plane_state->plane->type != DRM_PLANE_TYPE_PRIMARY) {
> +		drm_dbg_atomic(prop->dev,
> +			       "[OBJECT:%d] Only primary planes can be changed during async flip\n",
> +			       obj->id);
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
>  
>  int drm_atomic_set_property(struct drm_atomic_state *state,
>  			    struct drm_file *file_priv,
> @@ -1100,7 +1137,6 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
>  	case DRM_MODE_OBJECT_PLANE: {
>  		struct drm_plane *plane = obj_to_plane(obj);
>  		struct drm_plane_state *plane_state;
> -		struct drm_mode_config *config = &plane->dev->mode_config;
>  
>  		plane_state = drm_atomic_get_plane_state(state, plane);
>  		if (IS_ERR(plane_state)) {
> @@ -1108,19 +1144,11 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
>  			break;
>  		}
>  
> -		if (async_flip && prop != config->prop_fb_id) {
> -			ret = drm_atomic_plane_get_property(plane, plane_state,
> -							    prop, &old_val);
> -			ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
> -			break;
> -		}
> -
> -		if (async_flip && plane_state->plane->type != DRM_PLANE_TYPE_PRIMARY) {
> -			drm_dbg_atomic(prop->dev,
> -				       "[OBJECT:%d] Only primary planes can be changed during async flip\n",
> -				       obj->id);
> -			ret = -EINVAL;
> -			break;
> +		if (async_flip) {
> +			ret = drm_atomic_check_plane_changes(prop, plane, plane_state,

Should there be "async" somewhere in the name of
drm_atomic_check_plane_changes()?


Thanks,
pq

> +							     obj, prop_value, old_val);
> +			if (ret)
> +				break;
>  		}
>  
>  		ret = drm_atomic_plane_set_property(plane,
> diff --git a/include/drm/drm_atomic_uapi.h b/include/drm/drm_atomic_uapi.h
> index 4c6d39d7bdb2..d65fa8fbbca0 100644
> --- a/include/drm/drm_atomic_uapi.h
> +++ b/include/drm/drm_atomic_uapi.h
> @@ -29,6 +29,8 @@
>  #ifndef DRM_ATOMIC_UAPI_H_
>  #define DRM_ATOMIC_UAPI_H_
>  
> +#include <linux/types.h>
> +
>  struct drm_crtc_state;
>  struct drm_display_mode;
>  struct drm_property_blob;
> @@ -37,6 +39,9 @@ struct drm_crtc;
>  struct drm_connector_state;
>  struct dma_fence;
>  struct drm_framebuffer;
> +struct drm_mode_object;
> +struct drm_property;
> +struct drm_plane;
>  
>  int __must_check
>  drm_atomic_set_mode_for_crtc(struct drm_crtc_state *state,
> @@ -53,4 +58,11 @@ int __must_check
>  drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
>  				  struct drm_crtc *crtc);
>  
> +int drm_atomic_plane_get_property(struct drm_plane *plane,
> +				  const struct drm_plane_state *state,
> +				  struct drm_property *property, uint64_t *val);
> +
> +int drm_atomic_check_prop_changes(int ret, uint64_t old_val, uint64_t prop_value,
> +				  struct drm_property *prop);
> +
>  #endif
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index c6565a6f9324..73dac8d76831 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -540,6 +540,11 @@ struct drm_plane_funcs {
>  	 */
>  	bool (*format_mod_supported)(struct drm_plane *plane, uint32_t format,
>  				     uint64_t modifier);
> +
> +	int (*check_async_props)(struct drm_property *prop, struct drm_plane *plane,
> +				 struct drm_plane_state *plane_state,
> +				 struct drm_mode_object *obj,
> +				 u64 prop_value, u64 old_val);
>  };
>  
>  /**


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