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Subject: Re: [PATCH v7 1/7] iommu/arm-smmu-v3: Make default domain type of
 HiSilicon PTT device to identity
To:     Will Deacon <will@kernel.org>
References: <20220407125841.3678-1-yangyicong@hisilicon.com>
 <20220407125841.3678-2-yangyicong@hisilicon.com>
 <20220510112326.GA27790@willie-the-truck>
From:   Yicong Yang <yangyicong@huawei.com>
Message-ID: <cfde7d29-bf1b-35c4-92d8-6cd1faabc4c7@huawei.com>
Date:   Tue, 10 May 2022 20:43:13 +0800
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On 2022/5/10 19:23, Will Deacon wrote:
> On Thu, Apr 07, 2022 at 08:58:35PM +0800, Yicong Yang wrote:
>> The DMA operations of HiSilicon PTT device can only work properly with
>> identical mappings. So add a quirk for the device to force the domain
>> as passthrough.
>>
>> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
>> ---
>>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
> 
> I still don't like this being part of the SMMU driver, but given that
> (a) Robin doesn't seem to agree with the objection and (b) you've been
> refreshing the patch series:
> 
> Acked-by: Will Deacon <will@kernel.org>
> 
> If you do respin, then:
> 
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> index 627a3ed5ee8f..5ec15ae2a9b1 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>> @@ -2839,6 +2839,21 @@ static int arm_smmu_dev_disable_feature(struct device *dev,
>>  	}
>>  }
> 
> It might be worth adding a brief comment here to explain what this device is
> and why it needs an identity mapping.
> 
>> +#define IS_HISI_PTT_DEVICE(pdev)	((pdev)->vendor == PCI_VENDOR_ID_HUAWEI && \
>> +					 (pdev)->device == 0xa12e)
> 

Will add a brief comment here in next version.

Thanks,
Yicong