[PATCH v2] drm/msm: adreno: Fix improper u64 division

[PATCH v2] drm/msm: adreno: Fix improper u64 division

[Sean Paul]

From: Sean Paul <seanpaul@chromium.org>

This patch uses the proper do_div() macro to perform u64 division and
guards against overflow if the result is too large for the unsigned long
return type

Changes in v2:
- Added a6xx to the patch
- Removed parens from denominator in a5xx

Fixes: de0a3d094de0 drm/msm: re-factor devfreq code
Cc: Sharat Masetty <smasetty@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
---
 drivers/gpu/drm/msm/adreno/a5xx_gpu.c | 12 +++++++-----
 drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 11 +++++++----
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
index 40b4f8a0ae6d..176d0169f331 100644
--- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
@@ -1438,18 +1438,20 @@ static struct msm_ringbuffer *a5xx_active_ring(struct msm_gpu *gpu)
 
 static unsigned long a5xx_gpu_busy(struct msm_gpu *gpu)
 {
-	u64 busy_cycles;
-	unsigned long busy_time;
+	u64 busy_cycles, busy_time;
 
 	busy_cycles = gpu_read64(gpu, REG_A5XX_RBBM_PERFCTR_RBBM_0_LO,
 			REG_A5XX_RBBM_PERFCTR_RBBM_0_HI);
 
-	busy_time = (busy_cycles - gpu->devfreq.busy_cycles) /
-		(clk_get_rate(gpu->core_clk) / 1000000);
+	busy_time = (busy_cycles - gpu->devfreq.busy_cycles);
+	do_div(busy_time, clk_get_rate(gpu->core_clk) / 1000000);
 
 	gpu->devfreq.busy_cycles = busy_cycles;
 
-	return busy_time;
+	if (WARN_ON(busy_time > ~0LU))
+		return ~0LU;
+
+	return (unsigned long)busy_time;
 }
 
 static const struct adreno_gpu_funcs funcs = {
diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index e4ac95f20ca7..ba5ae3140ab7 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -763,18 +763,21 @@ static unsigned long a6xx_gpu_busy(struct msm_gpu *gpu)
 {
 	struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
 	struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
-	u64 busy_cycles;
-	unsigned long busy_time;
+	u64 busy_cycles, busy_time;
 
 	busy_cycles = gmu_read64(&a6xx_gpu->gmu,
 			REG_A6XX_GMU_CX_GMU_POWER_COUNTER_XOCLK_0_L,
 			REG_A6XX_GMU_CX_GMU_POWER_COUNTER_XOCLK_0_H);
 
-	busy_time = ((busy_cycles - gpu->devfreq.busy_cycles) * 10) / 192;
+	busy_time = (busy_cycles - gpu->devfreq.busy_cycles) * 10;
+	do_div(busy_time, 192);
 
 	gpu->devfreq.busy_cycles = busy_cycles;
 
-	return busy_time;
+	if (WARN_ON(busy_time > ~0LU))
+		return ~0LU;
+
+	return (unsigned long)busy_time;
 }
 
 static const struct adreno_gpu_funcs funcs = {
-- 
Sean Paul, Software Engineer, Google / Chromium OS

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