linux-kernel - [PATCH v9 1/2] drm/atomic: Let drivers decide which planes to async flip

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Message-Id: <20241002-tonyk-async_flip-v9-1-453b1b8977bd@igalia.com>
Date: Wed, 02 Oct 2024 18:16:05 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>, 
 Rodrigo Siqueira <Rodrigo.Siqueira@....com>, 
 Alex Deucher <alexander.deucher@....com>, 
 Christian König <christian.koenig@....com>, 
 Xinhui Pan <Xinhui.Pan@....com>, dmitry.baryshkov@...aro.org, 
 Simon Ser <contact@...rsion.fr>, joshua@...ggi.es, 
 Xaver Hugl <xaver.hugl@...il.com>, Daniel Stone <daniel@...ishbar.org>, 
 ville.syrjala@...ux.intel.com
Cc: kernel-dev@...lia.com, dri-devel@...ts.freedesktop.org, 
 linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org, 
 André Almeida <andrealmeid@...lia.com>
Subject: [PATCH v9 1/2] drm/atomic: Let drivers decide which planes to
 async flip

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.

Signed-off-by: André Almeida <andrealmeid@...lia.com>
---
Changes from v8:
- Rebased on top of 6.12-rc1
---
 drivers/gpu/drm/drm_atomic_uapi.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index 7936c2023955..b004fa1d2e2e 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>
@@ -1063,6 +1064,7 @@ 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)) {
@@ -1070,15 +1072,32 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
 			break;
 		}
 
-		if (async_flip &&
-		    (plane_state->plane->type != DRM_PLANE_TYPE_PRIMARY ||
-		     (prop != config->prop_fb_id &&
-		      prop != config->prop_in_fence_fd &&
-		      prop != config->prop_fb_damage_clips))) {
-			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) {
+			/* check if the prop does a nop change */
+			if ((plane_state->plane->type != DRM_PLANE_TYPE_PRIMARY) ||
+			    (prop != config->prop_fb_id &&
+			     prop != config->prop_in_fence_fd &&
+			     prop != config->prop_fb_damage_clips)) {
+				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;
+			}
+
+			/* ask the driver if this non-primary plane is supported */
+			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;
+				}
+			}
 		}
 
 		ret = drm_atomic_plane_set_property(plane,

-- 
2.46.0