linux-kernel - Re: [PATCH v3 1/4] iommu/arm-smmu: introduction of ACTLR for custom prefetcher settings

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Message-ID: <cfbf33cd-0faf-47c6-8e0f-b13c088670df@linaro.org>
Date:   Mon, 27 Nov 2023 16:33:47 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bibek Kumar Patro <quic_bibekkum@...cinc.com>, will@...nel.org,
        robin.murphy@....com, joro@...tes.org, dmitry.baryshkov@...aro.org,
        a39.skl@...il.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_pkondeti@...cinc.com,
        quic_molvera@...cinc.com
Cc:     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 v3 1/4] iommu/arm-smmu: introduction of ACTLR for custom
 prefetcher settings

On 27.11.2023 15:54, 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 prefetch setting of 1/3/7/15 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 | 56 +++++++++++++++++++++-
>  drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h |  6 ++-
>  drivers/iommu/arm/arm-smmu/arm-smmu.c      |  5 +-
>  drivers/iommu/arm/arm-smmu/arm-smmu.h      |  5 ++
>  4 files changed, 68 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 7f52ac67495f..4a38cae29be2 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -14,6 +14,12 @@
> 
>  #define QCOM_DUMMY_VAL	-1
> 
> +struct actlr_config {
> +	u16 sid;
> +	u16 mask;
> +	u32 actlr;
> +};
> +
>  static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
>  {
>  	return container_of(smmu, struct qcom_smmu, smmu);
> @@ -205,10 +211,40 @@ static bool qcom_adreno_can_do_ttbr1(struct arm_smmu_device *smmu)
>  	return true;
>  }
> 
> +static void arm_smmu_set_actlr(struct device *dev, struct arm_smmu_device *smmu, int cbndx,
> +		const struct actlr_config *actlrcfg, size_t actlrcfg_size)
> +{
> +	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> +	struct arm_smmu_master_cfg *cfg = dev_iommu_priv_get(dev);
> +	struct arm_smmu_smr *smr;
> +	int i;
> +	int j;
> +	u16 id;
> +	u16 mask;
> +	int idx;
> +
> +	for (i = 0; i < actlrcfg_size; ++i) {
> +		id = (actlrcfg + i)->sid;
> +		mask = (actlrcfg + i)->mask;
actrlcfg[i].id?

> +
> +		for_each_cfg_sme(cfg, fwspec, j, idx) {
> +			smr = &smmu->smrs[idx];
> +			if (smr_is_subset(*smr, id, mask))
Any reason for this value to be a pointer?

> +				arm_smmu_cb_write(smmu, cbndx, ARM_SMMU_CB_ACTLR,
> +						(actlrcfg + i)->actlr);
ditto

> +		}
> +	}
> +}
> +
>  static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>  		struct io_pgtable_cfg *pgtbl_cfg, struct device *dev)
>  {
>  	struct adreno_smmu_priv *priv;
> +	struct arm_smmu_device *smmu = smmu_domain->smmu;
> +	struct qcom_smmu *qsmmu = to_qcom_smmu(smmu);
> +	const struct actlr_config *actlrcfg;
> +	size_t actlrcfg_size;
> +	int cbndx = smmu_domain->cfg.cbndx;
Reverse-Christmas-tree sorting, please

> 
>  	smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
> 
> @@ -238,6 +274,12 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
>  	priv->set_stall = qcom_adreno_smmu_set_stall;
>  	priv->resume_translation = qcom_adreno_smmu_resume_translation;
> 
> +	if (qsmmu->data->actlrcfg_gfx) {
> +		actlrcfg = qsmmu->data->actlrcfg_gfx;
> +		actlrcfg_size = qsmmu->data->actlrcfg_gfx_size;
These can be passed directly s arm_smmu_set_actrl arguments

> +		arm_smmu_set_actlr(dev, smmu, cbndx, actlrcfg, actlrcfg_size);
> +	}
> +
>  	return 0;
>  }
> 
> @@ -263,6 +305,18 @@ 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_config *actlrcfg;
> +	size_t actlrcfg_size;
> +	int cbndx = smmu_domain->cfg.cbndx;
> +
> +	if (qsmmu->data->actlrcfg) {
> +		actlrcfg = qsmmu->data->actlrcfg;
> +		actlrcfg_size = qsmmu->data->actlrcfg_size;
> +		arm_smmu_set_actlr(dev, smmu, cbndx, actlrcfg, actlrcfg_size);
ditto

Konrad