linux-kernel - Re: [PATCH RESEND v8 1/2] drm/atomic: Let drivers decide which planes to async flip

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Message-ID: <h2nyiovf5ixbqjrmtqcofmj6uwigcps7yjwfu67j3xdewnoj5x@fyu6ee7qjgk4>
Date: Fri, 20 Sep 2024 15:28:38 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: André Almeida <andrealmeid@...lia.com>
Cc: dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, kernel-dev@...lia.com, alexander.deucher@....com, 
	christian.koenig@....com, Simon Ser <contact@...rsion.fr>, 
	Pekka Paalanen <ppaalanen@...il.com>, daniel@...ll.ch, Daniel Stone <daniel@...ishbar.org>, 
	'Marek Olšák' <maraeo@...il.com>, Dave Airlie <airlied@...il.com>, ville.syrjala@...ux.intel.com, 
	Xaver Hugl <xaver.hugl@...il.com>, Joshua Ashton <joshua@...ggi.es>, 
	Michel Dänzer <michel.daenzer@...lbox.org>
Subject: Re: [PATCH RESEND v8 1/2] drm/atomic: Let drivers decide which
 planes to async flip

On Tue, Aug 06, 2024 at 10:52:59AM GMT, André Almeida wrote:
> Currently, DRM atomic uAPI allows only primary planes to be flipped
> asynchronously. However, each driver might be able to perform async
> flips in other different plane types. To enable drivers to set their own
> restrictions on which type of plane they can or cannot flip, use the
> existing atomic_async_check() from struct drm_plane_helper_funcs to
> enhance this flexibility, thus allowing different plane types to be able
> to do async flips as well.
> 
> In order to prevent regressions and such, we keep the current policy: we
> skip the driver check for the primary plane, because it is always
> allowed to do async flips on it.

Unfortunately this needs to be rebased on top of 929725bd7eb4
("drm/atomic: allow no-op FB_ID updates for async flips"), but the
approach looks good to me and it fits the existing API.

> 
> Signed-off-by: André Almeida <andrealmeid@...lia.com>
> ---
>  drivers/gpu/drm/drm_atomic_uapi.c | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index fc16fddee5c5..8568c2428670 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -27,8 +27,9 @@
>   * Daniel Vetter <daniel.vetter@...ll.ch>
>   */
>  
> -#include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_atomic.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_drv.h>
> @@ -1059,6 +1060,7 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
>  		struct drm_plane *plane = obj_to_plane(obj);
>  		struct drm_plane_state *plane_state;
>  		struct drm_mode_config *config = &plane->dev->mode_config;
> +		const struct drm_plane_helper_funcs *plane_funcs = plane->helper_private;
>  
>  		plane_state = drm_atomic_get_plane_state(state, plane);
>  		if (IS_ERR(plane_state)) {
> @@ -1073,11 +1075,20 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
>  			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;
> +		if (async_flip) {
> +			/* we always allow primary planes */
> +			if (plane->type != DRM_PLANE_TYPE_PRIMARY) {
> +				ret = -EINVAL;
> +
> +				if (plane_funcs && plane_funcs->atomic_async_check)
> +					ret = plane_funcs->atomic_async_check(plane, state);
> +
> +				if (ret) {
> +					drm_dbg_atomic(prop->dev,
> +						       "[PLANE:%d] does not support async flips\n",
> +							obj->id);
> +				}
> +			}
>  			break;
>  		}
>  
> -- 
> 2.46.0
> 

-- 
With best wishes
Dmitry