linux-kernel - Re: [PATCH] RDMA/hns: Use dma_alloc_coherent() instead of kmalloc/dma_map

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Message-ID: <20211009104246.GA1205@LAPTOP-UKSR4ENP.internal.baidu.com>
Date:   Sat, 9 Oct 2021 18:42:46 +0800
From:   Cai Huoqing <caihuoqing@...du.com>
To:     Wenpeng Liang <liangwenpeng@...wei.com>
CC:     Jason Gunthorpe <jgg@...dia.com>, Lijun Ou <oulijun@...wei.com>,
        "Weihang Li" <liweihang@...wei.com>,
        Doug Ledford <dledford@...hat.com>,
        <linux-rdma@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RDMA/hns: Use dma_alloc_coherent() instead of
 kmalloc/dma_map_single()

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@...du.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