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

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Message-ID: <hdel47qqf4tto34a5atbjyukameoweudywixuj24aisqoikhcq@v523pootitbg>
Date: Fri, 20 Sep 2024 19:20:46 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
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 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.


> +		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
> 

-- 
With best wishes
Dmitry