[PATCH 1/2] drm/fb_cma_helper: Add drm_fb_cma_setup_fence() helper

[Marek Vasut <marex@denx.de>]

Add new drm_fb_cma_setup_fence() helper function extracted from the
imx-drm driver. This function checks if the plane has DMABUF attached
to it and if so, sets up the fence on which the atomic helper can wait.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
---
 drivers/gpu/drm/drm_fb_cma_helper.c | 26 ++++++++++++++++++++++++++
 include/drm/drm_fb_cma_helper.h     |  3 +++
 2 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
index 1fd6eac..2441707 100644
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -23,8 +23,10 @@
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_gem_cma_helper.h>
 #include <drm/drm_fb_cma_helper.h>
+#include <linux/dma-buf.h>
 #include <linux/dma-mapping.h>
 #include <linux/module.h>
+#include <linux/reservation.h>
 
 #define DEFAULT_FBDEFIO_DELAY_MS 50
 
@@ -265,6 +267,30 @@ struct drm_gem_cma_object *drm_fb_cma_get_gem_obj(struct drm_framebuffer *fb,
 }
 EXPORT_SYMBOL_GPL(drm_fb_cma_get_gem_obj);
 
+/**
+ * drm_fb_cma_setup_fence() - Set up the fence for atomic helper to wait on
+ * @plane: Which plane
+ * @state: Plane state to check
+ *
+ * If the plane fb has an dma-buf attached, fish out the exclusive
+ * fence for the atomic helper to wait on.
+ */
+void drm_fb_cma_setup_fence(struct drm_plane *plane,
+			    struct drm_plane_state *state)
+{
+	struct dma_buf *dma_buf;
+
+	if ((plane->state->fb == state->fb) || !state->fb)
+		return;
+
+	dma_buf = drm_fb_cma_get_gem_obj(state->fb, 0)->base.dma_buf;
+	if (!dma_buf)
+		return;
+
+	state->fence = reservation_object_get_excl_rcu(dma_buf->resv);
+}
+EXPORT_SYMBOL_GPL(drm_fb_cma_setup_fence);
+
 #ifdef CONFIG_DEBUG_FS
 static void drm_fb_cma_describe(struct drm_framebuffer *fb, struct seq_file *m)
 {
diff --git a/include/drm/drm_fb_cma_helper.h b/include/drm/drm_fb_cma_helper.h
index f313211..fc122d3 100644
--- a/include/drm/drm_fb_cma_helper.h
+++ b/include/drm/drm_fb_cma_helper.h
@@ -41,6 +41,9 @@ struct drm_framebuffer *drm_fb_cma_create(struct drm_device *dev,
 struct drm_gem_cma_object *drm_fb_cma_get_gem_obj(struct drm_framebuffer *fb,
 	unsigned int plane);
 
+void drm_fb_cma_setup_fence(struct drm_plane *plane,
+			    struct drm_plane_state *state);
+
 #ifdef CONFIG_DEBUG_FS
 struct seq_file;
 
-- 
2.9.3

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