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

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Date: Wed, 10 Jan 2024 18:56:51 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>,
 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, qipl.kernel.upstream@...cinc.com
Subject: Re: [PATCH v7 3/5] iommu/arm-smmu: introduction of ACTLR for custom
 prefetcher settings



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)


[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 :)

Konrad