Messages in this thread | | | Date | Mon, 26 May 2008 19:28:12 -0700 (PDT) | Subject | Re: MMIO and gcc re-ordering issue | From | David Miller <> |
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From: Benjamin Herrenschmidt <benh@kernel.crashing.org> Date: Tue, 27 May 2008 12:15:40 +1000
> Some of them. USB comes to mind. I'd be happy to make it "the rule" and > document that MMIO vs. coherent access aren't implicitely ordered. I > would still keep them ordered on powerpc for a little while tho until > I'm happy enough with driver auditing. > > But heh, it's you who was telling me that it would be a bad engineering > decision and we had to make everybody look like x86 & fully ordered :-) > I decided to agree back then and stuck all those nasty heavy barriers > in the powerpc variants of readl/writel/...
I still believe this.
It's just another complicated thing for driver authors to get wrong. The other side of the coin is of course the cost.
The only thing I am absolutely sure of is that we should make a decision fast, document it, and just stick to it.
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