1 files changed, 204 insertions, 0 deletions
diff --git a/drivers/dma-buf/dma-fence-unwrap.c b/drivers/dma-buf/dma-fence-unwrap.c
new file mode 100644
index 000000000000..a495d8a6c2e3
--- /dev/null
+++ b/drivers/dma-buf/dma-fence-unwrap.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * dma-fence-util: misc functions for dma_fence objects
+ *
+ * Copyright (C) 2022 Advanced Micro Devices, Inc.
+ * Authors:
+ *	Christian König <christian.koenig@amd.com>
+ */
+
+#include <linux/dma-fence.h>
+#include <linux/dma-fence-array.h>
+#include <linux/dma-fence-chain.h>
+#include <linux/dma-fence-unwrap.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+
+/* Internal helper to start new array iteration, don't use directly */
+static struct dma_fence *
+__dma_fence_unwrap_array(struct dma_fence_unwrap *cursor)
+{
+	cursor->array = dma_fence_chain_contained(cursor->chain);
+	cursor->index = 0;
+	return dma_fence_array_first(cursor->array);
+}
+
+/**
+ * dma_fence_unwrap_first - return the first fence from fence containers
+ * @head: the entrypoint into the containers
+ * @cursor: current position inside the containers
+ *
+ * Unwraps potential dma_fence_chain/dma_fence_array containers and return the
+ * first fence.
+ */
+struct dma_fence *dma_fence_unwrap_first(struct dma_fence *head,
+					 struct dma_fence_unwrap *cursor)
+{
+	cursor->chain = dma_fence_get(head);
+	return __dma_fence_unwrap_array(cursor);
+}
+EXPORT_SYMBOL_GPL(dma_fence_unwrap_first);
+
+/**
+ * dma_fence_unwrap_next - return the next fence from a fence containers
+ * @cursor: current position inside the containers
+ *
+ * Continue unwrapping the dma_fence_chain/dma_fence_array containers and return
+ * the next fence from them.
+ */
+struct dma_fence *dma_fence_unwrap_next(struct dma_fence_unwrap *cursor)
+{
+	struct dma_fence *tmp;
+
+	++cursor->index;
+	tmp = dma_fence_array_next(cursor->array, cursor->index);
+	if (tmp)
+		return tmp;
+
+	cursor->chain = dma_fence_chain_walk(cursor->chain);
+	return __dma_fence_unwrap_array(cursor);
+}
+EXPORT_SYMBOL_GPL(dma_fence_unwrap_next);
+
+
+static int fence_cmp(const void *_a, const void *_b)
+{
+	struct dma_fence *a = *(struct dma_fence **)_a;
+	struct dma_fence *b = *(struct dma_fence **)_b;
+
+	if (a->context < b->context)
+		return -1;
+	else if (a->context > b->context)
+		return 1;
+
+	if (dma_fence_is_later(b, a))
+		return 1;
+	else if (dma_fence_is_later(a, b))
+		return -1;
+
+	return 0;
+}
+
+/**
+ * dma_fence_dedup_array - Sort and deduplicate an array of dma_fence pointers
+ * @fences:     Array of dma_fence pointers to be deduplicated
+ * @num_fences: Number of entries in the @fences array
+ *
+ * Sorts the input array by context, then removes duplicate
+ * fences with the same context, keeping only the most recent one.
+ *
+ * The array is modified in-place and unreferenced duplicate fences are released
+ * via dma_fence_put(). The function returns the new number of fences after
+ * deduplication.
+ *
+ * Return: Number of unique fences remaining in the array.
+ */
+int dma_fence_dedup_array(struct dma_fence **fences, int num_fences)
+{
+	int i, j;
+
+	sort(fences, num_fences, sizeof(*fences), fence_cmp, NULL);
+
+	/*
+	 * Only keep the most recent fence for each context.
+	 */
+	j = 0;
+	for (i = 1; i < num_fences; i++) {
+		if (fences[i]->context == fences[j]->context)
+			dma_fence_put(fences[i]);
+		else
+			fences[++j] = fences[i];
+	}
+
+	return ++j;
+}
+EXPORT_SYMBOL_GPL(dma_fence_dedup_array);
+
+/* Implementation for the dma_fence_merge() marco, don't use directly */
+struct dma_fence *__dma_fence_unwrap_merge(unsigned int num_fences,
+					   struct dma_fence **fences,
+					   struct dma_fence_unwrap *iter)
+{
+	struct dma_fence *tmp, *unsignaled = NULL, **array;
+	struct dma_fence_array *result;
+	ktime_t timestamp;
+	int i, count;
+
+	count = 0;
+	timestamp = ns_to_ktime(0);
+	for (i = 0; i < num_fences; ++i) {
+		dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) {
+			if (!dma_fence_is_signaled(tmp)) {
+				dma_fence_put(unsignaled);
+				unsignaled = dma_fence_get(tmp);
+				++count;
+			} else {
+				ktime_t t = dma_fence_timestamp(tmp);
+
+				if (ktime_after(t, timestamp))
+					timestamp = t;
+			}
+		}
+	}
+
+	/*
+	 * If we couldn't find a pending fence just return a private signaled
+	 * fence with the timestamp of the last signaled one.
+	 *
+	 * Or if there was a single unsignaled fence left we can return it
+	 * directly and early since that is a major path on many workloads.
+	 */
+	if (count == 0)
+		return dma_fence_allocate_private_stub(timestamp);
+	else if (count == 1)
+		return unsignaled;
+
+	dma_fence_put(unsignaled);
+
+	array = kmalloc_array(count, sizeof(*array), GFP_KERNEL);
+	if (!array)
+		return NULL;
+
+	count = 0;
+	for (i = 0; i < num_fences; ++i) {
+		dma_fence_unwrap_for_each(tmp, &iter[i], fences[i]) {
+			if (!dma_fence_is_signaled(tmp)) {
+				array[count++] = dma_fence_get(tmp);
+			} else {
+				ktime_t t = dma_fence_timestamp(tmp);
+
+				if (ktime_after(t, timestamp))
+					timestamp = t;
+			}
+		}
+	}
+
+	if (count == 0 || count == 1)
+		goto return_fastpath;
+
+	count = dma_fence_dedup_array(array, count);
+
+	if (count > 1) {
+		result = dma_fence_array_create(count, array,
+						dma_fence_context_alloc(1),
+						1, false);
+		if (!result) {
+			for (i = 0; i < count; i++)
+				dma_fence_put(array[i]);
+			tmp = NULL;
+			goto return_tmp;
+		}
+		return &result->base;
+	}
+
+return_fastpath:
+	if (count == 0)
+		tmp = dma_fence_allocate_private_stub(timestamp);
+	else
+		tmp = array[0];
+
+return_tmp:
+	kfree(array);
+	return tmp;
+}
+EXPORT_SYMBOL_GPL(__dma_fence_unwrap_merge);