[RFC v3 8/8] drm/atomic: add ASYNC_UPDATE flag to the Atomic IOCTL

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.com>

This flag tells core to jump ahead the queued update if the conditions in
drm_atomic_async_check() are met. That means we are only able to do an
async update if no modeset is pending and update for the same plane is not
queued.

It uses the already in place infrastructure for async updates.

It is useful for cursor updates and async PageFlips over the atomic
ioctl, otherwise in some cases updates may be delayed to the point the user
will notice it.

DRM_MODE_ATOMIC_ASYNC_UPDATE should be passed to the Atomic IOCTL to use
this feature.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
---
 drivers/gpu/drm/drm_atomic.c | 8 +++++++-
 include/uapi/drm/drm_mode.h  | 4 +++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 259a758..304dd0a 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -77,6 +77,7 @@ drm_atomic_state_init(struct drm_device *dev, struct drm_atomic_state *state)
 	 * setting this appropriately?
 	 */
 	state->allow_modeset = true;
+	state->async_update = true;
 
 	state->crtcs = kcalloc(dev->mode_config.num_crtc,
 			       sizeof(*state->crtcs), GFP_KERNEL);
@@ -1653,7 +1654,7 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
 		}
 	}
 
-	if (state->legacy_cursor_update)
+	if (state->async_update || state->legacy_cursor_update)
 		state->async_update = drm_atomic_async_check(state);
 
 	return ret;
@@ -2189,6 +2190,10 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 			(arg->flags & DRM_MODE_PAGE_FLIP_EVENT))
 		return -EINVAL;
 
+	if ((arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET) &&
+			(arg->flags & DRM_MODE_ATOMIC_ASYNC_UPDATE))
+		return -EINVAL;
+
 	drm_modeset_acquire_init(&ctx, 0);
 
 	state = drm_atomic_state_alloc(dev);
@@ -2197,6 +2202,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
 
 	state->acquire_ctx = &ctx;
 	state->allow_modeset = !!(arg->flags & DRM_MODE_ATOMIC_ALLOW_MODESET);
+	state->async_update = !!(arg->flags & DRM_MODE_ATOMIC_ASYNC_UPDATE);
 
 retry:
 	plane_mask = 0;
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 8c67fc0..7c067ca 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -646,13 +646,15 @@ struct drm_mode_destroy_dumb {
 #define DRM_MODE_ATOMIC_TEST_ONLY 0x0100
 #define DRM_MODE_ATOMIC_NONBLOCK  0x0200
 #define DRM_MODE_ATOMIC_ALLOW_MODESET 0x0400
+#define DRM_MODE_ATOMIC_ASYNC_UPDATE 0x0800
 
 #define DRM_MODE_ATOMIC_FLAGS (\
 		DRM_MODE_PAGE_FLIP_EVENT |\
 		DRM_MODE_PAGE_FLIP_ASYNC |\
 		DRM_MODE_ATOMIC_TEST_ONLY |\
 		DRM_MODE_ATOMIC_NONBLOCK |\
-		DRM_MODE_ATOMIC_ALLOW_MODESET)
+		DRM_MODE_ATOMIC_ALLOW_MODESET |\
+		DRM_MODE_ATOMIC_ASYNC_UPDATE)
 
 struct drm_mode_atomic {
 	__u32 flags;
-- 
2.9.3

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