Re: [PATCH v18 2/4] iommu/arm-smmu: Add a way for implementations to influence SCTLR

Robin Murphy
2020-11-02T18:19:07Z

On 2020-11-02 17:14, Jordan Crouse wrote:
> From: Rob Clark <robdclark@chromium.org>
>
> For the Adreno GPU's SMMU, we want SCTLR.HUPCF set to ensure that
> pending translations are not terminated on iova fault. Otherwise
> a terminated CP read could hang the GPU by returning invalid
> command-stream data.
>
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> ---
>
> drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 6 ++++++
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 3 +++
> drivers/iommu/arm/arm-smmu/arm-smmu.h | 3 +++
> 3 files changed, 12 insertions(+)
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 1e942eed2dfc..0663d7d26908 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -129,6 +129,12 @@ static int qcom_adreno_smmu_init_context(struct arm_smmu_domain *smmu_domain,
> (smmu_domain->cfg.fmt == ARM_SMMU_CTX_FMT_AARCH64))
> pgtbl_cfg->quirks |= IO_PGTABLE_QUIRK_ARM_TTBR1;
>
> + /*
> + * On the GPU device we want to process subsequent transactions after a
> + * fault to keep the GPU from hanging
> + */
> + smmu_domain->cfg.sctlr_set |= ARM_SMMU_SCTLR_HUPCF;
> +
> /*
> * Initialize private interface with GPU:
> */
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> index dad7fa86fbd4..1f06ab219819 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> @@ -617,6 +617,9 @@ void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
> if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN))
> reg |= ARM_SMMU_SCTLR_E;
>
> + reg |= cfg->sctlr_set;
> + reg &= ~cfg->sctlr_clr;

Since we now have a write_s2cr hook, I'm inclined to think that the
consistency of a write_sctlr hook that could similarly apply its own
arbitrary tweaks would make sense for this. Does anyone have any strong
opinions?

Robin.

> +
> arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, reg);
> }
>
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> index 6c5ff9999eae..ddf2ca4c923d 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> @@ -144,6 +144,7 @@ enum arm_smmu_cbar_type {
> #define ARM_SMMU_CB_SCTLR 0x0
> #define ARM_SMMU_SCTLR_S1_ASIDPNE BIT(12)
> #define ARM_SMMU_SCTLR_CFCFG BIT(7)
> +#define ARM_SMMU_SCTLR_HUPCF BIT(8)
> #define ARM_SMMU_SCTLR_CFIE BIT(6)
> #define ARM_SMMU_SCTLR_CFRE BIT(5)
> #define ARM_SMMU_SCTLR_E BIT(4)
> @@ -341,6 +342,8 @@ struct arm_smmu_cfg {
> u16 asid;
> u16 vmid;
> };
> + u32 sctlr_set; /* extra bits to set in SCTLR */
> + u32 sctlr_clr; /* bits to mask in SCTLR */
> enum arm_smmu_cbar_type cbar;
> enum arm_smmu_context_fmt fmt;
> };