Re: [PATCH 2/2] drm/msm/a6xx: Use CX AO Counter register for timestamp on a750 GPUs

[Neil Armstrong]

On 9/9/26 20:31, Akhil P Oommen wrote:

On 9/8/2026 6:54 PM, Neil Armstrong wrote:

The a750 uses the CX AO Counters instead of the GMU_ALWAYS_ON_COUNTER
register on A6xx and other A7xx GPUs, use it when running a A750 GPU.

Do you see any difference in behavior? Both counters are synchronized.

GMU_ALWAYS_ON_COUNTER_H/L returns 0 on SM8650

Neil

-Akhil.

Signed-off-by: Neil Armstrong <neil.armstr...@linaro.org>
---
  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 12 +++++++++---
  1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c 
b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
index f9de9329dee3..081e79ea4652 100644
--- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
@@ -23,9 +23,15 @@ static u64 a6xx_gmu_get_timestamp(struct msm_gpu *gpu)
        u64 count_hi, count_lo, temp;

do {

-               count_hi = gmu_read(&a6xx_gpu->gmu, 
REG_A6XX_GMU_ALWAYS_ON_COUNTER_H);
-               count_lo = gmu_read(&a6xx_gpu->gmu, 
REG_A6XX_GMU_ALWAYS_ON_COUNTER_L);
-               temp = gmu_read(&a6xx_gpu->gmu, 
REG_A6XX_GMU_ALWAYS_ON_COUNTER_H);
+               if (adreno_is_a750_family(adreno_gpu)) {
+                       count_hi = gmu_read(&a6xx_gpu->gmu, 
REG_A7XX_GMU_CX_AO_COUNTER_H);
+                       count_lo = gmu_read(&a6xx_gpu->gmu, 
REG_A7XX_GMU_CX_AO_COUNTER_L);
+                       temp = gmu_read(&a6xx_gpu->gmu, 
REG_A7XX_GMU_CX_AO_COUNTER_H);
+               } else {
+                       count_hi = gmu_read(&a6xx_gpu->gmu, 
REG_A6XX_GMU_ALWAYS_ON_COUNTER_H);
+                       count_lo = gmu_read(&a6xx_gpu->gmu, 
REG_A6XX_GMU_ALWAYS_ON_COUNTER_L);
+                       temp = gmu_read(&a6xx_gpu->gmu, 
REG_A6XX_GMU_ALWAYS_ON_COUNTER_H);
+               }
        } while (unlikely(count_hi != temp));

return (count_hi << 32) | count_lo;