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

[Neil Armstrong <neil.armstrong@linaro.org>]

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.armstrong@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;
>>
>