On Wednesday, March 08, 2006 7:45 pm, Paul Mackerras wrote: > If we can have the following rules: > > * If you have stores to regular memory, followed by an MMIO store, > and you want the device to see the stores to regular memory at the > point where it receives the MMIO store, then you need a wmb() between > the stores to regular memory and the MMIO store. > > * If you have PIO or MMIO accesses, and you need to ensure the > PIO/MMIO accesses don't get reordered with respect to PIO/MMIO > accesses on another CPU, put the accesses inside a spin-locked > region, and put a mmiowb() between the last access and the > spin_unlock. > > * smp_wmb() doesn't necessarily do any ordering of MMIO accesses > vs. other accesses, and in that sense it is weaker than wmb().
This is a good set of rules. Hopefully David can add something like this to his doc. > ... then I can remove the sync from write*, which would be nice, and > make mmiowb() be a sync. I wonder how long we're going to spend > chasing driver bugs after that, though. :) Hm, a static checker should be able to find this stuff, shouldn't it? Jesse - To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
