[RFC 4/8] drm/fence: add in-fences support

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@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.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/gpu/drm/Kconfig             | 1 +
 drivers/gpu/drm/drm_atomic.c        | 8 ++++++++
 drivers/gpu/drm/drm_atomic_helper.c | 5 +++++
 drivers/gpu/drm/drm_crtc.c          | 7 +++++++
 include/drm/drm_crtc.h              | 1 +
 5 files changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index f2a74d0..3c987e3 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 8ee1db8..6702502 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>
 
 /**
  * drm_atomic_state_default_release -
@@ -680,6 +681,11 @@ 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) {
+		state->fence = sync_file_fences_get(val);
+		if (!state->fence)
+			return -EINVAL;
+		fence_get(state->fence);
 	} 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);
@@ -737,6 +743,8 @@ 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) {
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index f85ef8c..6ed8339 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -2687,6 +2687,11 @@ void __drm_atomic_helper_plane_destroy_state(struct drm_plane *plane,
 {
 	if (state->fb)
 		drm_framebuffer_unreference(state->fb);
+
+	if (state->fence) {
+		fence_put(state->fence);
+		state->fence = NULL;
+	}
 }
 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 55ffde5..65212ce 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1278,6 +1278,7 @@ 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);
@@ -1533,6 +1534,12 @@ 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 8cb377c..5ba3cda 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -2122,6 +2122,7 @@ struct drm_mode_config {
 	struct drm_property *prop_crtc_w;
 	struct drm_property *prop_crtc_h;
 	struct drm_property *prop_fb_id;
+	struct drm_property *prop_fence_fd;
 	struct drm_property *prop_crtc_id;
 	struct drm_property *prop_active;
 	struct drm_property *prop_mode_id;
-- 
2.5.5