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

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Message-ID: <f8f84113-c6f0-706c-cc87-4b57bacea059@collabora.com>
Date:   Mon, 14 Nov 2022 11:48:56 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Robin Murphy <robin.murphy@....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

Il 11/11/22 16:18, Robin Murphy ha scritto:
> 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.
> 

The spec says "configurations" -> implementation defined whether the system
implements stage 1 translation.... and that's how I got confused about it, sorry.

Thanks for the review, this clears up my doubts: I can reset FSR without caring
about FSRRESTORE.
I'll send a v3 ASAP.

Regards,
Angelo

> 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