linux-kernel - Re: [PATCH v2 3/8] iommu/arm-smmu: Add definition for ARM_SMMU_CB

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Date:   Fri, 11 Nov 2022 15:18:10 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, agross@...nel.org
Cc:     andersson@...nel.org, konrad.dybcio@...aro.org, joro@...tes.org,
        will@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, robdclark@...il.com,
        linux-arm-msm@...r.kernel.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        marijn.suijten@...ainline.org, kernel@...labora.com,
        luca@...tu.xyz, a39.skl@...il.com, phone-devel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v2 3/8] iommu/arm-smmu: Add definition for
 ARM_SMMU_CB_FSRRESTORE

On 11/11/2022 2:59 pm, AngeloGioacchino Del Regno wrote:
> In preparation for adding a proper context bank reset sequence in
> qcom_iommu, add a definition for the implementation defined Fault
> Status Restore register (FSRRESTORE).

It's not implementation defined, it's architectural. But I don't follow 
why we should need this. If we're resetting FSR, we don't need to 
restore any previous value to it; all we want to do is clear it, which 
we do already via its own mechanism.

Thanks,
Robin.

> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
>   drivers/iommu/arm/arm-smmu/arm-smmu.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> index 703fd5817ec1..5015138799c5 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> @@ -219,6 +219,7 @@ enum arm_smmu_cbar_type {
>   					 ARM_SMMU_FSR_TF |		\
>   					 ARM_SMMU_FSR_IGN)
>   
> +#define ARM_SMMU_CB_FSRRESTORE		0x5c
>   #define ARM_SMMU_CB_FAR			0x60
>   
>   #define ARM_SMMU_CB_FSYNR0		0x68