linux-kernel - Re: [PATCH v3 3/8] iommu/arm-smmu: Consult context bank allocator for identify domains

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Date:   Fri, 11 Sep 2020 08:24:22 +0000
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Rob Clark <robdclark@...omium.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 3/8] iommu/arm-smmu: Consult context bank allocator for
 identify domains

On 2020-09-04 21:25, Bjorn Andersson wrote:
> For implementations of the ARM SMMU where stream mappings of bypass 
> type
> are prohibited identity domains can be implemented by using context
> banks with translation disabled.
> 
> Postpone the decision to skip allocating a context bank until the
> implementation specific context bank allocator has been consulted and 
> if
> it decides to use a context bank for the identity map, don't enable
> translation (i.e. omit ARM_SMMU_SCTLR_M).
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> 

<snip>...

> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> index ddf2ca4c923d..235d9a3a6ab6 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> @@ -243,6 +243,8 @@ enum arm_smmu_cbar_type {
>  #define TLB_LOOP_TIMEOUT		1000000	/* 1s! */
>  #define TLB_SPIN_COUNT			10
> 
> +#define ARM_SMMU_CBNDX_BYPASS		0xffff
> +
>  /* Shared driver definitions */
>  enum arm_smmu_arch_version {
>  	ARM_SMMU_V1,
> @@ -346,6 +348,7 @@ struct arm_smmu_cfg {
>  	u32				sctlr_clr;    /* bits to mask in SCTLR */
>  	enum arm_smmu_cbar_type		cbar;
>  	enum arm_smmu_context_fmt	fmt;
> +	bool				m;

Can we use mmu_enable instead of m here to be more descriptive?

Thanks,
Sai

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