linux-kernel - Re: Opinion on ordering of writel vs. stores to RAM

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Date:	Sat, 09 Sep 2006 17:24:41 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Linus Torvalds <torvalds@...l.org>, linux-kernel@...r.kernel.org,
	akpm@...l.org, segher@...nel.crashing.org, davem@...emloft.net
Subject: Re: Opinion on ordering of writel vs. stores to RAM


> I suspect the best thing at this point is to move the sync in writeX()
> before the store, as you suggest, and add an "eieio" before the load
> in readX().  That does mean that we are then relying on driver writers
> putting in the mmiowb() between a writeX() and a spin_unlock, but at
> least that is documented.

Well, why keep the sync in writel then ? Isn't it agreed that the driver
should use an explicit barrier ? Or did I misunderstand Linus ?

Ben.


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