Re: [PATCH v7 3/5] iommu/arm-smmu: introduction of ACTLR for custom prefetcher settings

[Konrad Dybcio <konrad.dybcio@linaro.org>]

On 1/11/24 19:09, Bibek Kumar Patro wrote:
> 
> 
> On 1/10/2024 11:26 PM, Konrad Dybcio wrote:
>>
>>
>> On 1/10/24 13:55, Bibek Kumar Patro wrote:
>>>
>>>
>>> On 1/10/2024 4:46 PM, Bibek Kumar Patro wrote:
>>>>
>>>>
>>>> On 1/10/2024 9:36 AM, Pavan Kondeti wrote:
>>>
>>> [...]
>>>
>>>>>> @@ -274,6 +321,21 @@ static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
>>>>>>   static int qcom_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>>>>>           struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>>>>>>   {
>>>>>> +    struct arm_smmu_device *smmu = smmu_domain->smmu;
>>>>>> +    struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
>>>>>> +    const struct actlr_variant *actlrvar;
>>>>>> +    int cbndx = smmu_domain->cfg.cbndx;
>>>>>> +
>>>>>> +    if (qsmmu->data->actlrvar) {
>>>>>> +        actlrvar = qsmmu->data->actlrvar;
>>>>>> +        for (; actlrvar->io_start; actlrvar++) {
>>>>>> +            if (actlrvar->io_start == smmu->ioaddr) {
>>>>>> +                qcom_smmu_set_actlr(dev, smmu, cbndx, actlrvar->actlrcfg);
>>>>>> +                break;
>>>>>> +            }
>>>>>> +        }
>>>>>> +    }
>>>>>> +
>>>>>
>>>>> This block and the one in qcom_adreno_smmu_init_context() are exactly
>>>>> the same. Possible to do some refactoring?
>>>>>
>>>>
>>>> I will check if this repeated blocks can be accomodated this into qcom_smmu_set_actlr function if that would be fine.
>>>>
>>>
>>> Also adding to this, this might increase the number of indentation inside qcom_smmu_set_actlr as well, to around 5. So wouldn't this
>>> be an issue?
>>
>> By the way, we can refactor this:
>>
>> if (qsmmu->data->actlrvar) {
>>      actlrvar = qsmmu->data->actlrvar;
>>      for (; actlrvar->io_start; actlrvar++) {
>>          if (actlrvar->io_start == smmu->ioaddr) {
>>              qcom_smmu_set_actlr(dev, smmu, cbndx, actlrvar->actlrcfg);
>>              break;
>>          }
>>      }
>> }
>>
>> into
>>
>> // add const u8 num_actlrcfgs to struct actrl_variant to
>> // save on sentinel space:
>> //   sizeof(u8) < sizeof(ptr) + sizeof(resource_size_t)
>>
> 
> Git it, Would it be better to add this in struct qcom_smmu_match_data ?

Yes, right.

> Posted a sample below.
> 
>>
>> [declarations]
>> const struct actlr_variant *actlrvar = qsmmu->data->actlrvar;
>> int i;
>>
>> [rest of the functions]
>>
>> if (!actlrvar)
>>      return 0;
>>  > for (i = 0; i < actrlvar->num_actrlcfgs; i++) {
>>      if (actlrvar[i].io_start == smmu->ioaddr) {
>>          qcom_smmu_set_actlr(dev, smmu, cbndx, actlrvar->actlrcfg);
>>          break;
>>      }
>> }
>>  > Saving both on .TEXT size and indentation levels :)
>>
> Thanks for this suggestion Konrad, will try to implement this, as it would reduce the indent levels to good extent.
> Would something like this be okay?
> 
> static int qcom_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>       struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
>       const struct actlr_variant *actlrvar;
>       int cbndx = smmu_domain->cfg.cbndx;
> +    int i;
> 
> +    actlrvar = qsmmu->data->actlrvar;
> +
> +    if (!actlrvar)
> +        goto end;
> +
> +    for (i = 0; i < qsmmu->data->num_smmu ; i++) {
> +        if (actlrvar[i].io_start == smmu->ioaddr) {
> +            qcom_smmu_set_actlr(dev, smmu, cbndx,
> +                        actlrvar[i].actlrcfg);
> +            break;
>           }
>       }
> 
> +end:
>       smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;

If you move this assignment before the actlrvar checking (there's no
dependency between them), you will get rid of the goto.

I also noticed that qcom_smmu_match_data.actlrvar could likely be
const struct actlr_variant * const (const pointer to a const
resource), similarly for actlr_variant.actlrcfg

Konrad