[PATCH v2 3/5] accel/amdxdna: return early from a zero-length flush

SYNC_BO does not constrain its size, so a request for zero bytes reaches
amdxdna_flush_bo() and, on the vmap path, calls drm_clflush_virt_range()
with a length of zero. That helper flushes the line at end - 1 to
serialise, which for a zero length is the byte in front of the region
rather than anything the caller asked to maintain.

Nothing needs flushing for an empty range, so answer before choosing a
path.

Signed-off-by: Taimuraz Kaitmazov <[email protected]>
---
 drivers/accel/amdxdna/amdxdna_gem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/accel/amdxdna/amdxdna_gem.c b/drivers/accel/amdxdna/amdxdna_gem.c
index 1b8e90cd7..7df4bbb16 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.c
+++ b/drivers/accel/amdxdna/amdxdna_gem.c
@@ -1244,6 +1244,9 @@ static int amdxdna_flush_bo(struct amdxdna_gem_obj *abo, u64 offset, u64 size)
 		return -EINVAL;
 
 	size = min(abo->mem.size, end) - offset;
+	if (!size)
+		return 0;
+
 	if (is_import_bo(abo))
 		drm_clflush_sg(abo->base.sgt);
 	else if (amdxdna_gem_vmap(abo))
-- 
2.55.0