On Tue, Aug 20, 2013 at 01:06:25AM +0100, Mike Turquette wrote: > Quoting Mark Rutland (2013-08-19 02:35:43) > > On Sat, Aug 17, 2013 at 04:17:18PM +0100, Tomasz Figa wrote: > > > On Saturday 17 of August 2013 16:53:16 Sascha Hauer wrote: > > > > On Sat, Aug 17, 2013 at 02:28:04PM +0200, Tomasz Figa wrote: > > > > > > > > Also I would make this option required. Use a dummy clock for > > > > > > > > mux > > > > > > > > inputs that are grounded for a specific SoC. > > > > > > > > > > > > > > Some clocks are not from CCM and we haven't defined in > > > > > > > imx6q-clk.txt, > > > > > > > so in most cases we can't provide a phandle for them, eg: > > > > > > > spdif_ext. > > > > > > > I think it's a bit hard to force it to be 'required'. An > > > > > > > 'optional' > > > > > > > looks more flexible to me and a default one is ensured even if > > > > > > > it's > > > > > > > missing. > > > > > > > > > > > > <&clks 0> is the dummy clock. This can be used for all input clocks > > > > > > not > > > > > > defined by the SoC. > > > > > > > > > > Where does this assumption come from? Is it documented anywhere? > > > > > > > > This is how all i.MX clock bindings currently are. See > > > > Documentation/devicetree/bindings/clock/imx*-clock.txt > > > > > > OK, thanks. > > > > > > I guess we need some discussion on dummy clocks vs skipped clocks. I think > > > we want some consistency on this, don't we? > > > > > > If we really need a dummy clock, then we might also want a generic way to > > > specify it. > > > > What do we actually mean by a "dummy clock"? We already have bindings > > for "fixed-clock" and co friends describe relatively simple > > preconfigured clocks. > > Some platforms have a fake clock which defines noops callbacks and > basically doesn't do anything. This is analogous to the dummy regulator > implementation. A central one could be registered by the clock core, as > is done by the regulator core. When you say some platforms, you presumably mean the platform code in Linux? A dummy clock sounds like a completely Linux-specific abstraction rather than a description of the hardware, and I don't see why we need that in the DT: * If a clock is wired up and running (as presumably the dummy clock is), then surely it's a fixed-clock (it's running, we and we have no control over it, but we presumably know its rate) and can be described as such? * If no clock is wired up, then we should be able to describe that. If a driver believes that a clock is required when it isn't (for some level of functionality), then that driver should be fixed up to support the clock as being optional. Am I missing something? Thanks, Mark. -- 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
