Re: [PATCH v2 14/17] drm/msm/a8xx: Implement IFPC support for A840

[Akhil P Oommen]

On 3/27/2026 4:37 PM, Konrad Dybcio wrote:
> On 3/27/26 1:14 AM, Akhil P Oommen wrote:
>> Implement pwrup reglist support and add the necessary register
>> configurations to enable IFPC support on A840
>>
>> Signed-off-by: Akhil P Oommen <akhilpo@xxxxxxxxxxxxxxxx>
>> ---
> 
> [...]
> 
>> +	REG_A8XX_CP_PROTECT_GLOBAL(51),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(52),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(53),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(54),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(55),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(56),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(57),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(58),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(59),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(60),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(61),
>> +	REG_A8XX_CP_PROTECT_GLOBAL(62),
> 
> 53..62 aren't listed by kgsl, but I suppose this is more robust
> 
> Similarly for:
> 
> SP_CHICKEN_BITS_4
> RBBM_PERFCTR_CNTL

I can see SP_CHICKEN_BITS_4 in the recent kgsl code. RBBM_PERFCTR_CNTL
is required as we don't handle perfcounter management in this driver yet.

> 
> The other reglists look OK
> 
> [...]
> 
>> +	for (u32 pipe_id = PIPE_BR; pipe_id <= PIPE_DDE_BV; pipe_id++) {
>> +		for (i = 0; i < dyn_pwrup_reglist->count; i++) {
>> +			if (!(dyn_pwrup_reglist->regs[i].pipe & BIT(pipe_id)))
>> +				continue;
>> +			*dest++ = A8XX_CP_APERTURE_CNTL_HOST_PIPEID(pipe_id);
>> +			*dest++ = dyn_pwrup_reglist->regs[i].offset;
>> +			*dest++ = a8xx_read_pipe_slice(gpu,
>> +						       pipe_id,
>> +						       a8xx_get_first_slice(a6xx_gpu),
> 
> IDK if the compiler is smart enough to pick it up itself, but
> you could do const u32 first_slice = a8xx.. beforehand to save a
> couple cycles

This code is not called frequent enough to worry about micro optimizations.

> 
> [...]
> 
>> +	if (!a6xx_gpu->pwrup_reglist_emitted) {
>> +		a8xx_patch_pwrup_reglist(gpu);
>> +		a6xx_gpu->pwrup_reglist_emitted = true;
> 
> Would this flag be better set in the function above?

Agree, but we should update a6xx_gpu.c too. Lets do that separately.

-Akhil.

> 
> Konrad