Re: [PATCH 1/7] asm-generic/io.h: add io{read,write}64 accessors

[Vineet Gupta]

On Thursday 05 May 2016 04:26 PM, Arnd Bergmann wrote:
> On Thursday 05 May 2016 08:16:47 Vineet Gupta wrote:
>> > Thx for noticing this Arnd and the heads up. Does the patch below look ok to you ?
>> > 
>> > ----------->
>> > rom b7e719831c389ab4fa338b2e2e7c0d1ff90dabb0 Mon Sep 17 00:00:00 2001
>> > From: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>> > Date: Thu, 5 May 2016 13:32:34 +0530
>> > Subject: [PATCH] ARC: Add missing io barriers to io{read,write}{16,32}be()
>> > 
>> > While reviewing a different change to asm-generic/io.h Arnd spotted that
>> > ARC ioread32 and ioread32be both of which come from asm-generic versions
>> > are not symmetrical in terms of calling the io barriers.
>> > 
>> > generic ioread32   -> ARC readl()                  [ has barriers]
>> > generic ioread32be -> __be32_to_cpu(__raw_readl()) [ lacks barriers]
>> > 
>> > While generic ioread32be is being remediated to call readl(), that involves
>> > a swab32(), causing double swaps on ioread32be() on Big Endian systems.
>> > 
>> > So provide our versions of big endian IO accessors to ensure io barrier
>> > calls while also keeping them optimal
>> > 
>> > Suggested-by: Arnd Bergmann <arnd@xxxxxxxx>
>> > Cc: stable@xxxxxxxxxxxxxxx  [4.2+]
>> > Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>
> Yes, that looks correct. We probably want this regardless of the change
> I proposed for the generic file, to avoid the double swap.

Indeed so - I've queued this for 4.6 fixes !

> Acked-by: Arnd Bergmann <arnd@xxxxxxxx>

Thx !