Re: gpu: drm: msm: use div64_u64() instead of do_div()

From: Dmitry Baryshkov
Date: Wed Feb 09 2022 - 17:17:26 EST


On 09/02/2022 11:37, Qing Wang wrote:
From: Wang Qing <wangqing@xxxxxxxx>

do_div() does a 64-by-32 division.
When the divisor is u64, do_div() truncates it to 32 bits, this means it
can test non-zero and be truncated to zero for division.

fix do_div.cocci warning:
do_div() does a 64-by-32 division, please consider using div64_u64 instead.

Signed-off-by: Wang Qing <wangqing@xxxxxxxx>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>

---
drivers/gpu/drm/msm/msm_gpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index 2c1049c..aa4617b
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -648,7 +648,7 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
/* Calculate the clock frequency from the number of CP cycles */
if (elapsed) {
clock = (stats->cpcycles_end - stats->cpcycles_start) * 1000;
- do_div(clock, elapsed);
+ div64_u64(clock, elapsed);
}
trace_msm_gpu_submit_retired(submit, elapsed, clock,


--
With best wishes
Dmitry