linux-kernel - Re: [PATCH v15 4/5] iommu/arm-smmu: introduction of ACTLR for custom prefetcher settings

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Message-ID: <5d57669d-dce5-44de-963e-0997ac107c9b@quicinc.com>
Date: Sat, 21 Sep 2024 01:04:16 +0530
From: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: <robdclark@...il.com>, <will@...nel.org>, <robin.murphy@....com>,
        <joro@...tes.org>, <jgg@...pe.ca>, <jsnitsel@...hat.com>,
        <robh@...nel.org>, <krzysztof.kozlowski@...aro.org>,
        <quic_c_gdjako@...cinc.com>, <iommu@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v15 4/5] iommu/arm-smmu: introduction of ACTLR for custom
 prefetcher settings



On 9/20/2024 9:50 PM, Dmitry Baryshkov wrote:
> On Fri, Sep 20, 2024 at 09:28:12PM GMT, Bibek Kumar Patro wrote:
>> Currently in Qualcomm  SoCs the default prefetch is set to 1 which allows
>> the TLB to fetch just the next page table. MMU-500 features ACTLR
>> register which is implementation defined and is used for Qualcomm SoCs
>> to have a custom prefetch setting enabling TLB to prefetch the next set
>> of page tables accordingly allowing for faster translations.
>>
>> ACTLR value is unique for each SMR (Stream matching register) and stored
>> in a pre-populated table. This value is set to the register during
>> context bank initialisation.
>>
>> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 26 ++++++++++++++++++++++
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h |  1 +
>>   2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> index 38ac9cab763b..4ac272d05843 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
>> @@ -252,6 +252,20 @@ static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
>>   	return true;
>>   }
>>
>> +static void qcom_smmu_set_actlr_dev(struct device *dev, struct arm_smmu_device *smmu, int cbndx,
>> +		const struct of_device_id *client_match)
>> +{
>> +	const struct of_device_id *match =
>> +			of_match_device(client_match, dev);
>> +
>> +	if (!match) {
>> +		dev_notice(dev, "no ACTLR settings present\n");
> 
> dev_dbg() or even dev_vdbg(), please. We do not want to spam people with
> messages about a perfectly normal behaviour.
> 
> LGTM otherwise.

Ack, thanks Dmitry for the suggestion.
I was actually wondering if to broadcast this message
over the logs through dev_notice or give a option to
print it in debug level through dev_dbg.

But I'm inline with your suggestion now, will switch
to dev_dbg for this message.

Thanks & regards,
Bibek

> 
> 
>> +		return;
>> +	}
>> +
>> +	arm_smmu_cb_write(smmu, cbndx, ARM_SMMU_CB_ACTLR, (u64)match->data);
>> +}
>> +
>>   static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>>   		struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>>   {
>> @@ -316,8 +330,20 @@ 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 of_device_id *client_match;
>> +	int cbndx = smmu_domain->cfg.cbndx;
>> +
>>   	smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
>>
>> +	client_match = qsmmu->data->client_match;
>> +
>> +	if (!client_match)
>> +		return 0;
>> +
>> +	qcom_smmu_set_actlr_dev(dev, smmu, cbndx, client_match);
>> +
>>   	return 0;
>>   }
>>
>> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>> index b55cd3e3ae48..8addd453f5f1 100644
>> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
>> @@ -28,6 +28,7 @@ struct qcom_smmu_match_data {
>>   	const struct qcom_smmu_config *cfg;
>>   	const struct arm_smmu_impl *impl;
>>   	const struct arm_smmu_impl *adreno_impl;
>> +	const struct of_device_id * const client_match;
>>   };
>>
>>   irqreturn_t qcom_smmu_context_fault(int irq, void *dev);
>> --
>> 2.34.1
>>
>