netdev - Re: [PATCH net-next] sfc: Use __iowrite64_copy instead of a slightly different local function

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Date:	Tue, 29 Jul 2014 16:03:51 +0100
From:	Edward Cree <ecree@...arflare.com>
To:	Ben Hutchings <ben@...adent.org.uk>
CC:	Shradha Shah <sshah@...arflare.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] sfc: Use __iowrite64_copy instead of a slightly
 different local function

On 27/07/14 03:14, Ben Hutchings wrote:
> __iowrite64_copy() isn't quite the same as efx_memcpy_64(), but
> it looks close enough:
>
> - The length is in units of qwords not bytes
> - It never byte-swaps, but that doesn't make a difference now as PIO
>   is only enabled for x86_64
> - It doesn't include any memory barriers, but that's OK as there is a
>   barrier just before pushing the doorbell
> - mlx4_en uses it for the same purpose
>
> Compile-tested only.
>
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Acked-by: Edward Cree <ecree@...arflare.com>

On my test system, __iowrite64_copy compiles to use "mov    %rax,(%rdi)"
which we believe is safe (all writes will be naturally-aligned 64-bit
accesses, as required by the hardware).
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