drm/vc4: Syncobj import support

Allow userland to specify a syncobj that is waited on before a render job
starts processing.

v2: Use 0 as invalid syncobj to drop flag (Eric)
    Drop extra newline (Eric)
Signed-off-by: Stefan Schake <stschake@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/1524607427-12876-2-git-send-email-stschake@gmail.com

drivers/gpu/drm/vc4/vc4_drv.h

@@ -11,6 +11,7 @@
 #include <drm/drm_encoder.h>
 #include <drm/drm_gem_cma_helper.h>
 #include <drm/drm_atomic.h>
+#include <drm/drm_syncobj.h>
 
 #include "uapi/drm/vc4_drm.h"
 

drivers/gpu/drm/vc4/vc4_gem.c

@@ -27,6 +27,7 @@
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/sched/signal.h>
+#include <linux/dma-fence-array.h>
 
 #include "uapi/drm/vc4_drm.h"
 #include "vc4_drv.h"
@@ -1115,6 +1116,7 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 	struct drm_vc4_submit_cl *args = data;
 	struct vc4_exec_info *exec;
 	struct ww_acquire_ctx acquire_ctx;
+	struct dma_fence *in_fence;
 	int ret = 0;
 
 	if ((args->flags & ~(VC4_SUBMIT_CL_USE_CLEAR_COLOR |
@@ -1125,11 +1127,6 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 		return -EINVAL;
 	}
 
-	if (args->pad2 != 0) {
-		DRM_DEBUG("->pad2 must be set to zero\n");
-		return -EINVAL;
-	}
-
 	exec = kcalloc(1, sizeof(*exec), GFP_KERNEL);
 	if (!exec) {
 		DRM_ERROR("malloc failure on exec struct\n");
@@ -1164,6 +1161,29 @@ vc4_submit_cl_ioctl(struct drm_device *dev, void *data,
 		}
 	}
 
+	if (args->in_sync) {
+		ret = drm_syncobj_find_fence(file_priv, args->in_sync,
+					     &in_fence);
+		if (ret)
+			goto fail;
+
+		/* When the fence (or fence array) is exclusively from our
+		 * context we can skip the wait since jobs are executed in
+		 * order of their submission through this ioctl and this can
+		 * only have fences from a prior job.
+		 */
+		if (!dma_fence_match_context(in_fence,
+					     vc4->dma_fence_context)) {
+			ret = dma_fence_wait(in_fence, true);
+			if (ret) {
+				dma_fence_put(in_fence);
+				goto fail;
+			}
+		}
+
+		dma_fence_put(in_fence);
+	}
+
 	if (exec->args->bin_cl_size != 0) {
 		ret = vc4_get_bcl(dev, exec);
 		if (ret)

include/uapi/drm/vc4_drm.h

@@ -183,11 +183,10 @@ struct drm_vc4_submit_cl {
 	/* ID of the perfmon to attach to this job. 0 means no perfmon. */
 	__u32 perfmonid;
 
-	/* Unused field to align this struct on 64 bits. Must be set to 0.
-	 * If one ever needs to add an u32 field to this struct, this field
-	 * can be used.
+	/* Syncobj handle to wait on. If set, processing of this render job
+	 * will not start until the syncobj is signaled. 0 means ignore.
 	 */
-	__u32 pad2;
+	__u32 in_sync;
 };
 
 /**