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

[Konrad Dybcio]

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