Re: [PATCH 02/16] drm/msm/a6xx: Switch to preemption safe AO counter

[Konrad Dybcio]

On 3/25/26 10:46 PM, Akhil P Oommen wrote:
> On 3/24/2026 3:21 PM, Konrad Dybcio wrote:
>> On 3/23/26 9:12 PM, Akhil P Oommen wrote:
>>> CP_ALWAYS_ON_COUNTER is not save-restored during preemption, so it won't
>>> provide accurate data about the 'submit' when preemption is enabled.
>>> Switch to CP_ALWAYS_ON_CONTEXT which is preemption safe.
>>>
>>> Fixes: e7ae83da4a28 ("drm/msm/a6xx: Implement preemption for a7xx targets")
>>> Signed-off-by: Akhil P Oommen <akhilpo@xxxxxxxxxxxxxxxx>
>>> ---
>>>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 8 ++++----
>>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>> index 14d5b5e266f7..93bf2c40bfb9 100644
>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>>> @@ -345,7 +345,7 @@ static void a6xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>>>  	 * GPU registers so we need to add 0x1a800 to the register value on A630
>>>  	 * to get the right value from PM4.
>>>  	 */
>>> -	get_stats_counter(ring, REG_A6XX_CP_ALWAYS_ON_COUNTER,
>>> +	get_stats_counter(ring, REG_A6XX_CP_ALWAYS_ON_CONTEXT,
>>>  		rbmemptr_stats(ring, index, alwayson_start));
>>>  
>>>  	/* Invalidate CCU depth and color */
>>> @@ -386,7 +386,7 @@ static void a6xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>>>  
>>>  	get_stats_counter(ring, REG_A6XX_RBBM_PERFCTR_CP(0),
>>>  		rbmemptr_stats(ring, index, cpcycles_end));
>>> -	get_stats_counter(ring, REG_A6XX_CP_ALWAYS_ON_COUNTER,
>>> +	get_stats_counter(ring, REG_A6XX_CP_ALWAYS_ON_CONTEXT,
>>>  		rbmemptr_stats(ring, index, alwayson_end));
>>>  
>>>  	/* Write the fence to the scratch register */
>>> @@ -478,10 +478,10 @@ static void a7xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>>>  
>>>  	if (adreno_is_a8xx(adreno_gpu)) {
>>>  		rbbm_perfctr_cp0 = REG_A8XX_RBBM_PERFCTR_CP(0);
>>> -		cp_always_on_counter = REG_A8XX_CP_ALWAYS_ON_COUNTER;
>>> +		cp_always_on_counter = REG_A8XX_CP_ALWAYS_ON_CONTEXT;
>>
>> I'm a little worried about mixing the names here - KGSL uses both of
>> these registers (A6XX_KERNEL_PROFILE vs A6XX_KERNEL_PROFILE_CONTEXT)
>> to track different fields of the struct adreno_drawobj_profile_entry
> 
> But this naming aligns with the HW reg spec. So I prefer to use the same.

To make it clear, my confusion comes from:

cp_always_on_counter = REG_A8XX_CP_ALWAYS_ON_CONTEXT
             ^^^^^^^    vs                   ^^^^^^^

i.e. I'm not saying this is wrong, but rather that the local variable
could be renamed as well, to match

Konrad