linux-kernel - Re: [PATCH] sata_sil: add Large Block Transfer support

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Date:	Tue, 23 Dec 2008 13:40:28 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Robert Hancock <hancockr@...w.ca>
CC:	ide <linux-ide@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sata_sil: add Large Block Transfer support

Hello, Robert.

Robert Hancock wrote:
> Tejun Heo wrote:
>>
>> ioread/iowrite?
> 
> We know the register's always MMIO on this controller, so it's slightly
> more optimal to avoid the conditional in there.

Yeah, by a small margin but I think the consensus was to use
ioread/write no matter what if it's mapped using iomap.  I don't think
we guarantee iomapped address == mmio address after all.

>> I know it's not specific to this change but does mb() really make
>> sense here?  I don't think we need any barrier here.
> 
> Not sure. Documentation/memory-barriers.txt seems rather unfortunately
> vague on whether MMIO writes are strongly ordered with respect to memory
> writes. I seem to recall some debate on this a while ago, did it ever
> get resolved?

I remember that thread too but don't really any definite conclusion.
Eh... I hate barriers lying around without exact explanation.  :-(

Thanks.

-- 
tejun
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