[PATCH 5/6] drm/radeon: validate relocations in the order determined by userspace

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

Userspace should set the first 4 bits of drm_radeon_cs_reloc::flags to
a number from 0 to 15. The higher the number, the higher the priority,
which means a buffer with a higher number will be validated sooner.

The old behavior is preserved: Buffers used for write are prioritized over
read-only buffers if the userspace doesn't set the number.

Signed-off-by: Marek Olšák <marek.olsak at amd.com>
---
 drivers/gpu/drm/radeon/radeon.h        |  2 +-
 drivers/gpu/drm/radeon/radeon_cs.c     | 53 ++++++++++++++++++++++++++++++++--
 drivers/gpu/drm/radeon/radeon_object.c | 10 -------
 drivers/gpu/drm/radeon/radeon_object.h |  2 --
 4 files changed, 51 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index d37a57a..f7a3174 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -481,7 +481,7 @@ struct radeon_bo_list {
 	struct ttm_validate_buffer tv;
 	struct radeon_bo	*bo;
 	uint64_t		gpu_offset;
-	bool			written;
+	unsigned		priority;
 	unsigned		domain;
 	unsigned		alt_domain;
 	u32			tiling_flags;
diff --git a/drivers/gpu/drm/radeon/radeon_cs.c b/drivers/gpu/drm/radeon/radeon_cs.c
index d49a3f7..1ba1a48 100644
--- a/drivers/gpu/drm/radeon/radeon_cs.c
+++ b/drivers/gpu/drm/radeon/radeon_cs.c
@@ -31,6 +31,41 @@
 #include "radeon.h"
 #include "radeon_trace.h"
 
+/* This is a variation of the bucket sort with O(n) time complexity.
+ * The relocations are sorted from the highest to the lowest priority. */
+static void sort_relocs_for_validation(struct list_head *list)
+{
+	struct list_head bucket[17], *it, *tmp;
+	unsigned i, priority;
+
+	for (i = 0; i < 17; i++)
+		INIT_LIST_HEAD(&bucket[i]);
+
+	/* Move the elements into buckets. An i-th bucket only contains
+	 * elements with priorities i*2 and i*2+1. Odd numbers are added
+	 * at the head of a bucket and even numbers are added at the tail,
+	 * therefore all buckets are always sorted. */
+	list_for_each_safe(it, tmp, list) {
+		priority = list_entry(it, struct radeon_bo_list,
+				      tv.head)->priority;
+		i = priority / 2;
+		i = min(i, 16u) ;
+
+		if (priority % 2 == 1) {
+			list_move(it, &bucket[i]);
+		} else {
+			list_move_tail(it, &bucket[i]);
+		}
+	}
+
+	INIT_LIST_HEAD(list);
+
+	/* connect the sorted buckets */
+	for (i = 0; i < 17; i++) {
+		list_splice(&bucket[i], list);
+	}
+}
+
 static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 {
 	struct drm_device *ddev = p->rdev->ddev;
@@ -80,7 +115,15 @@ static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 		p->relocs_ptr[i] = &p->relocs[i];
 		p->relocs[i].robj = gem_to_radeon_bo(p->relocs[i].gobj);
 		p->relocs[i].lobj.bo = p->relocs[i].robj;
-		p->relocs[i].lobj.written = !!r->write_domain;
+
+		/* The userspace buffer priorities are from 0 to 15. A higher
+		 * number means the buffer is more important.
+		 * Also, the buffers used for write have a higher priority than
+		 * the buffers used for read only, which doubles the range
+		 * to 0 to 31. Numbers 32 and 33 are reserved for the kernel
+		 * driver.
+		 */
+		p->relocs[i].lobj.priority = (r->flags & 0xf) * 2 + !!r->write_domain;
 
 		/* the first reloc of an UVD job is the msg and that must be in
 		   VRAM, also but everything into VRAM on AGP cards to avoid
@@ -94,6 +137,8 @@ static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 			p->relocs[i].lobj.alt_domain =
 				RADEON_GEM_DOMAIN_VRAM;
 
+			/* prioritize this over any other relocation */
+			p->relocs[i].lobj.priority = 32;
 		} else {
 			uint32_t domain = r->write_domain ?
 				r->write_domain : r->read_domains;
@@ -107,9 +152,11 @@ static int radeon_cs_parser_relocs(struct radeon_cs_parser *p)
 		p->relocs[i].lobj.tv.bo = &p->relocs[i].robj->tbo;
 		p->relocs[i].handle = r->handle;
 
-		radeon_bo_list_add_object(&p->relocs[i].lobj,
-					  &p->validated);
+		list_add(&p->relocs[i].lobj.tv.head, &p->validated);
 	}
+
+	sort_relocs_for_validation(&p->validated);
+
 	return radeon_bo_list_validate(&p->ticket, &p->validated, p->ring);
 }
 
diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index d676ee2..19042ae 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -368,16 +368,6 @@ void radeon_bo_fini(struct radeon_device *rdev)
 	arch_phys_wc_del(rdev->mc.vram_mtrr);
 }
 
-void radeon_bo_list_add_object(struct radeon_bo_list *lobj,
-				struct list_head *head)
-{
-	if (lobj->written) {
-		list_add(&lobj->tv.head, head);
-	} else {
-		list_add_tail(&lobj->tv.head, head);
-	}
-}
-
 int radeon_bo_list_validate(struct ww_acquire_ctx *ticket,
 			    struct list_head *head, int ring)
 {
diff --git a/drivers/gpu/drm/radeon/radeon_object.h b/drivers/gpu/drm/radeon/radeon_object.h
index a9a8c11..6c3ca9e 100644
--- a/drivers/gpu/drm/radeon/radeon_object.h
+++ b/drivers/gpu/drm/radeon/radeon_object.h
@@ -138,8 +138,6 @@ extern int radeon_bo_evict_vram(struct radeon_device *rdev);
 extern void radeon_bo_force_delete(struct radeon_device *rdev);
 extern int radeon_bo_init(struct radeon_device *rdev);
 extern void radeon_bo_fini(struct radeon_device *rdev);
-extern void radeon_bo_list_add_object(struct radeon_bo_list *lobj,
-				struct list_head *head);
 extern int radeon_bo_list_validate(struct ww_acquire_ctx *ticket,
 				   struct list_head *head, int ring);
 extern int radeon_bo_fbdev_mmap(struct radeon_bo *bo,
-- 
1.8.3.2