On Wednesday 14 May 2014 08:45:23 Rob Herring wrote: > On Wed, May 14, 2014 at 8:18 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On Wednesday 14 May 2014 18:44:46 Viresh Kumar wrote: > >> On 14 May 2014 18:41, Heiko Stübner <heiko@xxxxxxxxx> wrote: > >> > Am Mittwoch, 14. Mai 2014, 18:35:29 schrieb Viresh Kumar: > >> >> On 14 May 2014 18:20, Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> >> > Could we please come up with a way to probe this from DT in the > >> >> > cpufreq-cpu0 driver itself, so we don't have to add a device in every > >> >> > platform using it? > >> > >> >> Its followed that way because DT Maintainers had strong objections > >> >> to creating virtual device nodes and haven't allowed creation of nodes > >> >> for cpufreq drivers.. For which there is no physical device, as CPU already > >> >> has a separate node.. > >> > > >> > as we already have the "enable-method" property for enabling/disabling cpus, > >> > would something like a "scaling-method" be feasible? > > > > Good idea to put it as a property into the CPU node. > > We already have properties which indicate this driver can be used by a > platform: opp table and a clock for the cpu. If this information is > not sufficient to determine whether you can use this driver or not, > then you simply need to match against the platform. Perhaps the match > list should be a blacklist rather than a whitelist, so new platforms > work without a kernel change. We'd not only need a blacklist, but also a way to tell whether we want to use the cpu0 or the big/little implementation, which currently have indistinguishable bindings. > Alternatively, create a new OPP binding that addresses this and all > the other limitations in the current OPP binding. Yes. > >> Lets see what DT maintainers have to say on this, I would rather go for a > >> more straight forward name: "scaling-driver" .. > > > > Both sound fine to me. > > The fact that linux needs a way to create a platform device to enable > a certain driver is not a DT problem. I proposed a solution for how to > get this out of the platform code [1], but evidently we want people to > open code the exceptions and adding boilerplate helpers will just > encourage the exceptions. I think the only benefit we have from using platform devices at all for cpufreq (not for cpuidle, which has a similar problem) is module autoloading. I think your patch doesn't actually help with that. 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
