From: okaya@codeaurora.org
To: David Miller <davem@davemloft.net>
Cc: linux-rdma@vger.kernel.org, timur@codeaurora.org,
cov@codeaurora.org, yishaih@mellanox.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] net: ethernet: mellanox: correct page conversion
Date: Mon, 18 Apr 2016 01:06:27 -0400 [thread overview]
Message-ID: <87c17d3f979cf0167cd37077f39d0534@codeaurora.org> (raw)
In-Reply-To: <20160418.000039.1946438541182822213.davem@davemloft.net>
On 2016-04-18 00:00, David Miller wrote:
> From: Sinan Kaya <okaya@codeaurora.org>
> Date: Sat, 16 Apr 2016 18:23:32 -0400
>
>> Current code is assuming that the address returned by
>> dma_alloc_coherent
>> is a logical address. This is not true on ARM/ARM64 systems. This
>> patch
>> replaces dma_alloc_coherent with dma_map_page API. The address
>> returned
>> can later by virtually mapped from the CPU side with vmap API.
>>
>> Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
>
> You can't do this.
>
> The DMA map page API gives non-coherent mappings, and thus requires
> proper flushing.
>
> So a straight conversion like this is never legitimate.
I would agree on proper dma api usage. However, the code is already
assuming coherent architecture by mapping the cpu pages as page_kernel.
Dma_map_page returns cached buffers and you don't need cache flushes on
coherent architecture to make the data visible.
next prev parent reply other threads:[~2016-04-18 5:06 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-16 22:23 [PATCH V2] net: ethernet: mellanox: correct page conversion Sinan Kaya
2016-04-18 4:00 ` David Miller
2016-04-18 5:06 ` okaya [this message]
2016-04-18 15:59 ` David Miller
2016-04-18 16:06 ` Sinan Kaya
2016-04-18 6:54 ` Eli Cohen
2016-04-18 13:53 ` Sinan Kaya
2016-04-18 14:05 ` Eli Cohen
2016-04-18 14:32 ` Christoph Hellwig
2016-04-18 14:39 ` Eli Cohen
2016-04-18 15:17 ` Christoph Hellwig
2016-04-18 15:21 ` Sinan Kaya
2016-04-18 15:40 ` Christoph Hellwig
2016-04-18 17:47 ` Sinan Kaya
2016-04-19 7:50 ` Sinan Kaya
2016-04-18 12:12 ` Christoph Hellwig
2016-04-18 13:06 ` okaya
2016-04-18 13:10 ` Christoph Hellwig
2016-04-18 13:49 ` Sinan Kaya
2016-04-18 13:59 ` Christoph Hellwig
2016-04-18 15:15 ` Timur Tabi
2016-04-18 15:22 ` Sinan Kaya
2016-04-19 18:22 ` Christoph Hellwig
2016-04-19 18:37 ` Sinan Kaya
2016-04-20 11:08 ` Eran Ben Elisha
2016-04-20 13:35 ` Sinan Kaya
2016-04-20 13:38 ` Sinan Kaya
2016-04-20 13:41 ` Timur Tabi
2016-04-20 18:40 ` Eran Ben Elisha
2016-04-20 18:42 ` Sinan Kaya
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