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Subject: Re: [PATCH v7 18/24] iommu/arm-smmu-v3: Add support for Hardware
 Translation Table Update
To:     Jean-Philippe Brucker <jean-philippe@linaro.org>,
        <iommu@lists.linux-foundation.org>, <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
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CC:     <fenghua.yu@intel.com>, <kevin.tian@intel.com>,
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References: <20200519175502.2504091-1-jean-philippe@linaro.org>
 <20200519175502.2504091-19-jean-philippe@linaro.org>
From:   Zenghui Yu <yuzenghui@huawei.com>
Message-ID: <472fdcf6-f306-60bc-5813-4ad421ee03f2@huawei.com>
Date:   Fri, 28 Aug 2020 17:28:22 +0800
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On 2020/5/20 1:54, Jean-Philippe Brucker wrote:
> @@ -4454,6 +4470,12 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
>   			smmu->features |= ARM_SMMU_FEAT_E2H;
>   	}
>   
> +	if (reg & (IDR0_HA | IDR0_HD)) {
> +		smmu->features |= ARM_SMMU_FEAT_HA;
> +		if (reg & IDR0_HD)
> +			smmu->features |= ARM_SMMU_FEAT_HD;
> +	}
> +

nitpick:

As per the IORT spec (DEN0049D, 3.1.1.2 SMMUv3 node, Table 10), the
"HTTU Override" flag of the SMMUv3 node can override the value in
SMMU_IDR0.HTTU. You may want to check this bit before selecting the
{HA,HD} features and shout if there is a mismatch between firmware and
the SMMU implementation. Just like how ARM_SMMU_FEAT_COHERENCY is
selected.


Thanks,
Zenghui