linux-kernel - Re: [PATCH 01/16] hpsa: do readl after writel in main i/o path to ensure commands don't get lost.

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Date:	Wed, 04 May 2011 13:54:22 -0400
From:	Valdis.Kletnieks@...edu
To:	Matthew Wilcox <matthew@....cx>
Cc:	scameron@...rdog.cce.hp.com, Tomas Henzl <thenzl@...hat.com>,
	james.bottomley@...senpartnership.com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, smcameron@...oo.com,
	akpm@...ux-foundation.org, mikem@...rdog.cce.hp.com
Subject: Re: [PATCH 01/16] hpsa: do readl after writel in main i/o path to ensure commands don't get lost.

On Wed, 04 May 2011 11:37:35 MDT, Matthew Wilcox said:
> > This probably needs a comment like
> > 	/* don't care - dummy read just to force write posting to chipset */
> > or similar.  I'm assuming it's just functioning as a barrier-type flush of some sort?
> 
> It's a PCI write flush.  It's not clear to me why it's needed here,
> though.  The write will eventually get to the device; why we need to
> make the CPU wait around for it to actually get there doesn't make sense.

Exactly why I think it needs a one-liner comment. :)



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