On Fri, 2015-06-26 at 15:41 -0700, Luis R. Rodriguez wrote: > > It wasn't nullified for the main user at the time, the fb. And I > > mentioned an IB adapter or two for which the code had been hand > tuned. > > This still means there could be some affected drivers when used on > powerpc, no?
Yes. In fact what about things like ARM who also have barriers in their writel() ? Won't they also break WC ? I'm trying to work with the architect and designers here to figure out exactly where we stand and what we can do. As spelled out by our architecture, things don't look great, because basically, we only have attribute bit (garded) which when not set implies both WC and out of order (& prefetch), and unclear barrier semantics in that case as well. I *think* we might be able to settle with something along the lines of "writel_relaxed() will allow combine on a WC mapping" but how I'm going to get there is TBD. It would be interesting to clarify the semantics of using the relaxed accessors in combination with WC anyway. I wouldn't mind if the definition involved also relaxing general ordering :-) It would definitely make my life easier. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
