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Re: [PATCH 1/2] ide: Add tx4939ide driver

To: James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: Re: [PATCH 1/2] ide: Add tx4939ide driver
From: Tejun Heo <htejun@gmail.com>
Date: Sat, 04 Oct 2008 11:56:21 +0900
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>, Atsushi Nemoto <anemo@mba.ocn.ne.jp>, sshtylyov@ru.mvista.com, linux-mips@linux-mips.org, linux-ide@vger.kernel.org, ralf@linux-mips.org, Jens Axboe <jens.axboe@oracle.com>
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James Bottomley wrote:
> On Sun, 2008-09-28 at 07:09 +0900, Tejun Heo wrote:
>> Bartlomiej Zolnierkiewicz wrote:
>>> On Friday 12 September 2008, Atsushi Nemoto wrote:
>>>> On Fri, 12 Sep 2008 19:34:06 +0400, Sergei Shtylyov 
>>>> <sshtylyov@ru.mvista.com> wrote:
>>> [...]
>>>
>>>>>>>> +      __ide_flush_dcache_range((unsigned long)addr, size);
>>>>>>>   Why is this needed BTW?
>>>>>> Do you mean __ide_flush_dcache_range?  This is needed to avoid cache
>>>>>> inconsistency on PIO drive.  PIO transfer only writes to cache but
>>>>>> upper layers expects the data is in main memory.
>>>>>     Hum, then I wonder why it's MIPS specific...
>>>> SPARC also have it.  And there were some discussions for ARM IIRC.
>>> I was under the impression that it has been addressed by Tejun at
>>> the higher-layer level (for both ide/libata) long time ago and that
>>> MIPS/SPARC code are just a left-overs which could be removed now?
>> cc'ing Jens and James.  IIRC, I posted several patches but they never
>> went in.  I don't remember what the objections were or whether any
>> alternative fix went in.
> 
> Which patches were these?  We have several methods of doing PIO
> fallback, the most common one being
> scatterlist.c:sg_copy_from/to_buffer() which does the cache coherency.

The thread Atsushi found seems to be the correct one.

  http://lkml.org/lkml/2006/1/13/156

Thanks.

-- 
tejun

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