[PATCH 4.19 303/338] drm/amdgpu: fix off by one in amdgpu_gfx_kiq_acquire()

[Greg Kroah-Hartman]

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

[ Upstream commit 1647b54ed55d4d48c7199d439f8834626576cbe9 ]

This post-op should be a pre-op so that we do not pass -1 as the bit
number to test_bit().  The current code will loop downwards from 63 to
-1.  After changing to a pre-op, it loops from 63 to 0.

Fixes: 71c37505e7ea ("drm/amdgpu/gfx: move more common KIQ code to amdgpu_gfx.c")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
index 239bf2a4b3c6..eeaa2e825858 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c
@@ -173,7 +173,7 @@ static int amdgpu_gfx_kiq_acquire(struct amdgpu_device *adev,
 		    * adev->gfx.mec.num_pipe_per_mec
 		    * adev->gfx.mec.num_queue_per_pipe;
 
-	while (queue_bit-- >= 0) {
+	while (--queue_bit >= 0) {
 		if (test_bit(queue_bit, adev->gfx.mec.queue_bitmap))
 			continue;
 
-- 
2.35.1