Hi Russell, On Wed, 25 Feb 2015, Russell King - ARM Linux wrote: > On Mon, Feb 23, 2015 at 10:12:23AM +0000, Peter Griffin wrote: > > I think all the writel IO accessors in this driver can be replaced > > with the *_relaxed variant. This will avoid the overhead of taking a > > spinlock in the l2 outer cache part of writel. > > You're really operating on old information. With much improved L2 cache > support code which went in a year or so ago, for the popular L2 cache > controllers, we don't take a spinlock anymore - we just write to the > register directly. > > The spinlock is only present for L2C-220 controllers, which are rare. > > Moreover, taking the spinlock is only expensive if you have things like > lockdep enabled, otherwise it should be inline and will be fast. > > However, using the _relaxed variants where we can get away with weaker > ordering of the writes to the device is a good thing nevertheless. I'm > just pointing out that your reasoning above is wrong. Thanks for pointing this out, I wasn't aware until now that the spinlock had been removed. regards Peter. -- 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
