linux-kernel - Re: [PATCH v7 1/7] iommu/arm-smmu-v3: Make default domain type of HiSilicon PTT device to identity

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Date:   Tue, 10 May 2022 20:43:13 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     Will Deacon <will@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <helgaas@...nel.org>,
        <alexander.shishkin@...ux.intel.com>, <lorenzo.pieralisi@....com>,
        <mark.rutland@....com>, <mathieu.poirier@...aro.org>,
        <suzuki.poulose@....com>, <mike.leach@...aro.org>,
        <leo.yan@...aro.org>, <jonathan.cameron@...wei.com>,
        <daniel.thompson@...aro.org>, <joro@...tes.org>,
        <john.garry@...wei.com>, <shameerali.kolothum.thodi@...wei.com>,
        <robin.murphy@....com>, <peterz@...radead.org>, <mingo@...hat.com>,
        <acme@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <coresight@...ts.linaro.org>, <linux-pci@...r.kernel.org>,
        <linux-perf-users@...r.kernel.org>,
        <iommu@...ts.linux-foundation.org>, <prime.zeng@...wei.com>,
        <liuqi115@...wei.com>, <zhangshaokun@...ilicon.com>,
        <linuxarm@...wei.com>
Subject: Re: [PATCH v7 1/7] iommu/arm-smmu-v3: Make default domain type of
 HiSilicon PTT device to identity

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@...ilicon.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@...nel.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