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Subject: Re: [PATCH] RDMA/hns: Use dma_alloc_coherent() instead of
 kmalloc/dma_map_single()
To:     Cai Huoqing <caihuoqing@baidu.com>
References: <20210926061116.282-1-caihuoqing@baidu.com>
 <20210927115913.GA3544071@ziepe.ca> <20211004195224.GA2576309@nvidia.com>
 <07922740-2d3d-50dc-7239-421e39c42142@huawei.com>
 <20211009104246.GA1205@LAPTOP-UKSR4ENP.internal.baidu.com>
CC:     Jason Gunthorpe <jgg@nvidia.com>, Lijun Ou <oulijun@huawei.com>,
        "Weihang Li" <liweihang@huawei.com>,
        Doug Ledford <dledford@redhat.com>,
        <linux-rdma@vger.kernel.org>, <linux-kernel@vger.kernel.org>
From:   Wenpeng Liang <liangwenpeng@huawei.com>
Message-ID: <28e67298-7ed5-399c-9052-d8c172e65062@huawei.com>
Date:   Sat, 9 Oct 2021 20:03:02 +0800
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On 2021/10/9 18:42, Cai Huoqing wrote:
> On 09 10月 21 17:50:50, Wenpeng Liang wrote:
>>
>>
>> On 2021/10/5 3:52, Jason Gunthorpe wrote:
>>> On Mon, Sep 27, 2021 at 08:59:13AM -0300, Jason Gunthorpe wrote:
>>>> On Sun, Sep 26, 2021 at 02:11:15PM +0800, Cai Huoqing wrote:
>>>>> Replacing kmalloc/kfree/dma_map_single/dma_unmap_single()
>>>>> with dma_alloc_coherent/dma_free_coherent() helps to reduce
>>>>> code size, and simplify the code, and coherent DMA will not
>>>>> clear the cache every time.
>>>>>
>>>>> Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
>>>>>  drivers/infiniband/hw/hns/hns_roce_hw_v2.c | 20 +++++---------------
>>>>>  1 file changed, 5 insertions(+), 15 deletions(-)
>>>>
>>>> Given I don't see any dma_sync_single calls for this mapping, isn't
>>>> this a correctness fix too?
>>>
>>> HNS folks?
>>>
>>> Jason
>>> .
>>>
>>
>> Our SoC can keep cache coherent, so there is no exception even if
>> dma_sync_single* is not called, but the driver should not make
>> assumptions about SoC.
>>
>> So using dma_alloc_coherent() instead of kmalloc/dma_map_single()
>> can simplify the code and achieve the same purpose.
>>
>> Wenpeng Liang
> 
> 
> Hi Liang
> 
> Thanks for your feedback.
> 
> If you think my patch is correct, you can give a Reviewed-by: to it.
> You can also give a Tested-by: to it, if the test on hardware was made.
> 
> Thanks
> Cai
> .
> 

Hi, Cai

After testing, it seems ok to me.

Reviewed-by: Wenpeng Liang <liangwenpeng@huawei.com>
Tested-by: Wenpeng Liang <liangwenpeng@huawei.com>

Thanks,
Wenpeng