[RFC v4 1/3] drm/fence: add in-fences support

[Gustavo Padovan]

From: Gustavo Padovan <gustavo.padovan at collabora.co.uk>

There is now a new property called FENCE_FD attached to every plane
state that receives the sync_file fd from userspace via the atomic commit
IOCTL.

The fd is then translated to a fence (that may be a fence_collection
subclass or just a normal fence) and then used by DRM to fence_wait() for
all fences in the sync_file to signal. So it only commits when all
framebuffers are ready to scanout.

v2: Comments by Daniel Vetter:
	- remove set state->fence = NULL in destroy phase
	- accept fence -1 as valid and just return 0
	- do not call fence_get() - sync_file_fences_get() already calls it
	- fence_put() if state->fence is already set, in case userspace
	set the property more than once.

v3: WARN_ON if fence is set but state has no FB

Signed-off-by: Gustavo Padovan <gustavo.padovan at collabora.co.uk>
---
 drivers/gpu/drm/Kconfig             |  1 +
 drivers/gpu/drm/drm_atomic.c        | 19 +++++++++++++++++++
 drivers/gpu/drm/drm_atomic_helper.c |  3 +++
 drivers/gpu/drm/drm_crtc.c          |  7 +++++++
 include/drm/drm_crtc.h              |  4 ++++
 5 files changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index c02be6a..07f9c60 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -12,6 +12,7 @@ menuconfig DRM
 	select I2C
 	select I2C_ALGOBIT
 	select DMA_SHARED_BUFFER
+	select SYNC_FILE
 	help
 	  Kernel-level support for the Direct Rendering Infrastructure (DRI)
 	  introduced in XFree86 4.0. If you say Y here, you need to select
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 5cb2e22..9e6c4e7 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -30,6 +30,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_mode.h>
 #include <drm/drm_plane_helper.h>
+#include <linux/sync_file.h>
 
 #include "drm_crtc_internal.h"
 
@@ -690,6 +691,17 @@ int drm_atomic_plane_set_property(struct drm_plane *plane,
 		drm_atomic_set_fb_for_plane(state, fb);
 		if (fb)
 			drm_framebuffer_unreference(fb);
+	} else if (property == config->prop_fence_fd) {
+		if (U642I64(val) == -1)
+			return 0;
+
+		if (state->fence)
+			fence_put(state->fence);
+
+		state->fence = sync_file_get_fence(val);
+		if (!state->fence)
+			return -EINVAL;
+
 	} else if (property == config->prop_crtc_id) {
 		struct drm_crtc *crtc = drm_crtc_find(dev, val);
 		return drm_atomic_set_crtc_for_plane(state, crtc);
@@ -749,6 +761,8 @@ drm_atomic_plane_get_property(struct drm_plane *plane,
 
 	if (property == config->prop_fb_id) {
 		*val = (state->fb) ? state->fb->base.id : 0;
+	} else if (property == config->prop_fence_fd) {
+		*val = -1;
 	} else if (property == config->prop_crtc_id) {
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->prop_crtc_x) {
@@ -824,6 +838,11 @@ static int drm_atomic_plane_check(struct drm_plane *plane,
 		return -EINVAL;
 	}
 
+	if (WARN_ON(state->fence && !state->fb)) {
+		DRM_DEBUG_ATOMIC("in-fence set but no FB\n");
+		return -EINVAL;
+	}
+
 	/* if disabled, we don't care about the rest of the state: */
 	if (!state->crtc)
 		return 0;
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index dff2389..f817452 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -3156,6 +3156,9 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane_state *state)
 {
 	if (state->fb)
 		drm_framebuffer_unreference(state->fb);
+
+	if (state->fence)
+		fence_put(state->fence);
 }
 EXPORT_SYMBOL(__drm_atomic_helper_plane_destroy_state);
 
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index b95c48ac..6eaeb73 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -338,6 +338,7 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
 
 	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
 		drm_object_attach_property(&plane->base, config->prop_fb_id, 0);
+		drm_object_attach_property(&plane->base, config->prop_fence_fd, -1);
 		drm_object_attach_property(&plane->base, config->prop_crtc_id, 0);
 		drm_object_attach_property(&plane->base, config->prop_crtc_x, 0);
 		drm_object_attach_property(&plane->base, config->prop_crtc_y, 0);
@@ -610,6 +611,12 @@ static int drm_mode_create_standard_properties(struct drm_device *dev)
 		return -ENOMEM;
 	dev->mode_config.prop_fb_id = prop;
 
+	prop = drm_property_create_signed_range(dev, DRM_MODE_PROP_ATOMIC,
+			"FENCE_FD", -1, INT_MAX);
+	if (!prop)
+		return -ENOMEM;
+	dev->mode_config.prop_fence_fd = prop;
+
 	prop = drm_property_create_object(dev, DRM_MODE_PROP_ATOMIC,
 			"CRTC_ID", DRM_MODE_OBJECT_CRTC);
 	if (!prop)
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 3d33c90..2dc7e79 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -1809,6 +1809,10 @@ struct drm_mode_config {
 	 */
 	struct drm_property *prop_fb_id;
 	/**
+ 	 * @prop_fence_fd: Sync File fd reprenseting the fences for this plane
+	 */
+	struct drm_property *prop_fence_fd;
+	/**
 	 * @prop_crtc_id: Default atomic plane property to specify the
 	 * &drm_crtc.
 	 */
-- 
2.5.5