Re: [PATCH 18/19] iommu/arm-smmu: add a way for implementations to influence SCTLR

[Bjorn Andersson]

On Thu 13 Aug 21:41 CDT 2020, Rob Clark wrote:

> From: Rob Clark <robdclark@xxxxxxxxxxxx>
> 
> 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.
> 

Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>

> Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> ---
>  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 5640d9960610..2aa6249050ff 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -127,6 +127,12 @@ 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 e63a480d7f71..bbec5793faf8 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;
> +
>  	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 cd75a33967bb..2df3a70a8a41 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;
>  };
> -- 
> 2.26.2
>