[RFC PATCH v2 1/3] drm/syncobj: Add flag DRM_SYNCOBJ_QUERY_FLAGS_ERROR to query errors

[Yicong Hui]

Add flag DRM_SYNCOBJ_QUERY_FLAGS_ERROR to make the
DRM_IOCTL_SYNCOBJ_QUERY ioctl fill out the handles array with the
error code of the first fence found per syncobj and 0 if one is not
found and maintain the normal return value in points.

Suggested-by: Christian König <christian.koenig@xxxxxxx>
Suggested-by: Michel Dänzer <michel.daenzer@xxxxxxxxxxx>
Signed-off-by: Yicong Hui <yiconghui@xxxxxxxxx>
---
 drivers/dma-buf/dma-fence-chain.c | 52 +++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_syncobj.c     | 21 ++++++++++++-
 include/linux/dma-fence-chain.h   |  1 +
 include/uapi/drm/drm.h            |  1 +
 4 files changed, 74 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/dma-fence-chain.c b/drivers/dma-buf/dma-fence-chain.c
index a8a90acf4f34..076d78b73379 100644
--- a/drivers/dma-buf/dma-fence-chain.c
+++ b/drivers/dma-buf/dma-fence-chain.c
@@ -76,6 +76,58 @@ struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence)
 }
 EXPORT_SYMBOL(dma_fence_chain_walk);
 
+/**
+ * dma_fence_chain_find_error - find the latest error
+ * @fence: current chain node
+ *
+ * Walk the chain repeatedly until reaches a fence with error, or the
+ * end of the fence chain. Does not garbage collect.
+ *
+ * Returns the first error it finds in the chain.
+ */
+int64_t dma_fence_chain_find_error(struct dma_fence *fence)
+{
+	struct dma_fence_chain *chain, *prev_chain;
+	struct dma_fence *prev;
+	int64_t error = 0;
+
+	chain = to_dma_fence_chain(fence);
+	if (!chain)
+		return fence->error;
+
+	if (chain->fence->error)
+		return chain->fence->error;
+
+	while ((prev = dma_fence_chain_get_prev(chain))) {
+		prev_chain = to_dma_fence_chain(prev);
+
+		if (prev_chain) {
+
+			if (prev_chain->fence->error) {
+				error = prev_chain->fence->error;
+				dma_fence_put(prev);
+				break;
+			}
+
+			chain = prev_chain;
+		} else {
+
+			if (prev->error)
+				error = prev->error;
+			dma_fence_put(prev);
+			break;
+		}
+
+
+		dma_fence_put(prev);
+
+	}
+
+
+	return error;
+}
+EXPORT_SYMBOL(dma_fence_chain_find_error);
+
 /**
  * dma_fence_chain_find_seqno - find fence chain node by seqno
  * @pfence: pointer to the chain node where to start
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 2d4ab745fdad..322f64b72775 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -1654,14 +1654,17 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_syncobj_timeline_array *args = data;
 	struct drm_syncobj **syncobjs;
+	unsigned int valid_flags = DRM_SYNCOBJ_QUERY_FLAGS_LAST_SUBMITTED |
+				   DRM_SYNCOBJ_QUERY_FLAGS_ERROR;
 	uint64_t __user *points = u64_to_user_ptr(args->points);
+	uint64_t __user *handles = u64_to_user_ptr(args->handles);
 	uint32_t i;
 	int ret;
 
 	if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ_TIMELINE))
 		return -EOPNOTSUPP;
 
-	if (args->flags & ~DRM_SYNCOBJ_QUERY_FLAGS_LAST_SUBMITTED)
+	if (args->flags & ~valid_flags)
 		return -EINVAL;
 
 	if (args->count_handles == 0)
@@ -1680,6 +1683,22 @@ int drm_syncobj_query_ioctl(struct drm_device *dev, void *data,
 		uint64_t point;
 
 		fence = drm_syncobj_fence_get(syncobjs[i]);
+
+		if (args->flags & DRM_SYNCOBJ_QUERY_FLAGS_ERROR) {
+			int64_t error = 0;
+
+			if (fence)
+				error = dma_fence_chain_find_error(fence);
+
+			ret = copy_to_user(&handles[i], &error, sizeof(int64_t));
+			ret = ret ? -EFAULT : 0;
+			if (ret) {
+				dma_fence_put(fence);
+				break;
+			}
+
+		}
+
 		chain = to_dma_fence_chain(fence);
 		if (chain) {
 			struct dma_fence *iter, *last_signaled =
diff --git a/include/linux/dma-fence-chain.h b/include/linux/dma-fence-chain.h
index 68c3c1e41014..b4ada124d7b6 100644
--- a/include/linux/dma-fence-chain.h
+++ b/include/linux/dma-fence-chain.h
@@ -122,6 +122,7 @@ static inline void dma_fence_chain_free(struct dma_fence_chain *chain)
 	     iter = dma_fence_chain_walk(iter))
 
 struct dma_fence *dma_fence_chain_walk(struct dma_fence *fence);
+int64_t dma_fence_chain_find_error(struct dma_fence *fence);
 int dma_fence_chain_find_seqno(struct dma_fence **pfence, uint64_t seqno);
 void dma_fence_chain_init(struct dma_fence_chain *chain,
 			  struct dma_fence *prev,
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 27cc159c1d27..2640cc0a09fe 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -1044,6 +1044,7 @@ struct drm_syncobj_array {
 };
 
 #define DRM_SYNCOBJ_QUERY_FLAGS_LAST_SUBMITTED (1 << 0) /* last available point on timeline syncobj */
+#define DRM_SYNCOBJ_QUERY_FLAGS_ERROR (1 << 1) /* fill out error codes if they are found */
 struct drm_syncobj_timeline_array {
 	__u64 handles;
 	__u64 points;
-- 
2.53.0