Re: [PATCH v7 18/24] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update - Jean-Philippe Brucker

From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Zenghui Yu <yuzenghui@huawei.com>
Cc: iommu@lists.linux-foundation.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org,
	linux-mm@kvack.org, fenghua.yu@intel.com, kevin.tian@intel.com,
	jacob.jun.pan@linux.intel.com, jgg@ziepe.ca,
	catalin.marinas@arm.com, joro@8bytes.org, robin.murphy@arm.com,
	hch@infradead.org, zhangfei.gao@linaro.org,
	Jonathan.Cameron@huawei.com, felix.kuehling@amd.com,
	xuzaibo@huawei.com, will@kernel.org, christian.koenig@amd.com,
	baolu.lu@linux.intel.com
Subject: Re: [PATCH v7 18/24] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update
Date: Wed, 16 Sep 2020 16:11:28 +0200	[thread overview]
Message-ID: <20200916141128.GC5316@myrica> (raw)
In-Reply-To: <472fdcf6-f306-60bc-5813-4ad421ee03f2@huawei.com>

On Fri, Aug 28, 2020 at 05:28:22PM +0800, Zenghui Yu wrote:
> 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 for pointing this out, I didn't know about these flags but have
added them to the patch now.

Thanks,
Jean