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

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Message-ID: <1a1f9b11-5a6d-41f7-8bcd-533a61a27a65@quicinc.com>
Date: Thu, 11 Jan 2024 23:39:36 +0530
From: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@...aro.org>,
        Pavan Kondeti
	<quic_pkondeti@...cinc.com>
CC: <will@...nel.org>, <robin.murphy@....com>, <joro@...tes.org>,
        <dmitry.baryshkov@...aro.org>, <jsnitsel@...hat.com>,
        <quic_bjorande@...cinc.com>, <mani@...nel.org>,
        <quic_eberman@...cinc.com>, <robdclark@...omium.org>,
        <u.kleine-koenig@...gutronix.de>, <robh@...nel.org>,
        <vladimir.oltean@....com>, <quic_molvera@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 3/5] iommu/arm-smmu: introduction of ACTLR for custom
 prefetcher settings



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 ?
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;

  	return 0;

Thanks & regards,
Bibek

> Konrad