On Tuesday 15 December 2015 15:09:23 Timur Tabi wrote: > Arnd Bergmann wrote: > > If that's in the probe() called from it function, just use writel() everywhere, > > a few extra microseconds won't kill the boot time. In general, if a user would > > notice the difference, use the relaxed version and add a comment to explain > > how you proved it's correct, otherwise stay with the default accessors. > > What about adding a wmb() after the last writel()? This driver does > that a lot. Is that something we want to discourage? I can understand > how we would want to make sure that the last write is posted before the > function exits. Please explain in a comment specifically which race you are closing by ensuring that the write gets posted. What does it race against? As I said earlier, guaranteeing that a write gets posted does not mean it has arrived at the device, we only get that behavior after a subsequent read from the same device, but you don't need a wmb() between the write and the read to guarantee this. If you have an odd bus that does not follow those rules, it may in fact be best to have a separate set of I/O accessors and not use readl/writel at all. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
