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Message-ID: <372885ab-b24d-44ae-afb8-76755bcd6e21@arm.com>
Date: Tue, 14 Nov 2023 16:55:30 +0000
From: Robin Murphy <robin.murphy@....com>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>, will@...nel.org,
joro@...tes.org, dmitry.baryshkov@...aro.org, a39.skl@...il.com,
konrad.dybcio@...aro.org, 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 v2 1/3] iommu/arm-smmu: introduction of ACTLR for custom
prefetcher settings
On 14/11/2023 1:56 pm, 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 | 41 ++++++++++++++++++++++
> drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h | 2 ++
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 5 +--
> drivers/iommu/arm/arm-smmu/arm-smmu.h | 5 +++
> 4 files changed, 51 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 549ae4dba3a6..578c662c7c30 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -14,6 +14,17 @@
>
> #define QCOM_DUMMY_VAL -1
>
> +struct actlr_config {
> + const struct actlr_data *adata;
> + size_t size;
> +};
> +
> +struct actlr_data {
> + u16 sid;
> + u16 mask;
Do we need to worry about masks? If you're already assuming that any SMR
will be programmed to match a superset of the data here, surely a single
unique ID per device would suffice?
> + u32 actlr;
> +};
> +
> static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
> {
> return container_of(smmu, struct qcom_smmu, smmu);
> @@ -261,9 +272,36 @@ static const struct of_device_id qcom_smmu_client_of_match[] __maybe_unused = {
> { }
> };
>
> +static void arm_smmu_set_actlr(struct arm_smmu_device *smmu, int idx,
> + const struct actlr_config *actlrcfg)
> +{
> + struct arm_smmu_smr *smr = smmu->smrs;
> + int i;
> + u16 id;
> + u16 mask;
> +
> + for (i = 0; i < actlrcfg->size; ++i) {
> + id = actlrcfg->adata[i].sid;
> + mask = actlrcfg->adata[i].mask;
> + if (!smr_is_subset(*smr, id, mask))
How well have you tested this? ;)
> + arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_ACTLR,
> + actlrcfg->adata[i].actlr);
> + }
> +}
> +
> 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;
> + int idx = smmu_domain->cfg.cbndx;
> +
> + if (qsmmu->actlrcfg) {
> + actlrcfg = qsmmu->actlrcfg;
> + arm_smmu_set_actlr(smmu, idx, actlrcfg);
> + }
> +
> smmu_domain->cfg.flush_walk_prefer_tlbiasid = true;
>
> return 0;
> @@ -467,6 +505,9 @@ static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,
> qsmmu->smmu.impl = impl;
> qsmmu->cfg = data->cfg;
>
> + if (data->actlrcfg && (data->actlrcfg->size))
> + qsmmu->actlrcfg = data->actlrcfg;
Do we really need to replicate multiple parts of the data, or would it
be sensible to just replace qsmmu->cfg with qsmmu->data and handle the
further dereferences in the places that want them?
> +
> return &qsmmu->smmu;
> }
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
> index 593910567b88..4b6862715070 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.h
> @@ -9,6 +9,7 @@
> struct qcom_smmu {
> struct arm_smmu_device smmu;
> const struct qcom_smmu_config *cfg;
> + const struct actlr_config *actlrcfg;
> bool bypass_quirk;
> u8 bypass_cbndx;
> u32 stall_enabled;
> @@ -25,6 +26,7 @@ struct qcom_smmu_config {
> };
>
> struct qcom_smmu_match_data {
> + const struct actlr_config *actlrcfg;
> const struct qcom_smmu_config *cfg;
> const struct arm_smmu_impl *impl;
> const struct arm_smmu_impl *adreno_impl;
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> index d6d1a2a55cc0..8e4faf015286 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> @@ -990,9 +990,10 @@ static int arm_smmu_find_sme(struct arm_smmu_device *smmu, u16 id, u16 mask)
> * expect simply identical entries for this case, but there's
> * no harm in accommodating the generalisation.
> */
> - if ((mask & smrs[i].mask) == mask &&
> - !((id ^ smrs[i].id) & ~smrs[i].mask))
> +
> + if (smr_is_subset(smrs[i], id, mask))
> return i;
> +
> /*
> * If the new entry has any other overlap with an existing one,
> * though, then there always exists at least one stream ID
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> index 703fd5817ec1..b1638bbc41d4 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> @@ -501,6 +501,11 @@ static inline void arm_smmu_writeq(struct arm_smmu_device *smmu, int page,
> writeq_relaxed(val, arm_smmu_page(smmu, page) + offset);
> }
>
> +static inline bool smr_is_subset(struct arm_smmu_smr smrs, u16 id, u16 mask)
Hmm, that name reads as implying the opposite of what it actually tests,
not to mention that passing structs by value is a bit horrid as well :(
Thanks,
Robin.
> +{
> + return (mask & smrs.mask) == mask && !((id ^ smrs.id) & ~smrs.mask);
> +}
> +
> #define ARM_SMMU_GR0 0
> #define ARM_SMMU_GR1 1
> #define ARM_SMMU_CB(s, n) ((s)->numpage + (n))
> --
> 2.17.1
>
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