Messages in this thread | | | Date | Tue, 23 Oct 2012 11:56:25 +0200 | From | Thierry Reding <> | Subject | Re: [PATCH 2/3] PWM: vt8500: Update vt8500 PWM driver support |
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On Tue, Oct 23, 2012 at 10:31:28AM +0100, Russell King - ARM Linux wrote: > On Tue, Oct 23, 2012 at 11:22:47AM +0200, Thierry Reding wrote: > > On Tue, Oct 23, 2012 at 09:41:46PM +1300, Tony Prisk wrote: > > > Further to the discussion, my preference is still for of_clk_get() > > > (although I've changed the patch anyway as you saw because it makes no > > > difference in this case) :) > > > > > > clk_get(x, NULL) and devm_clk_get(x, NULL) both seems like 'hacks' to > > > allow platforms to convert to DT without having to update all their > > > drivers first. It only allows the first (default) clock, as your pointed > > > out. Getting a 2nd... clock relies on an optional property in DT (which > > > again, seems like it is there to support 'old' drivers) which allows you > > > to request clocks by name. > > > > > > of_clk_get() on the other hand seems like a properly native DT function. > > > You don't need to know anything about the clock, as long as the correct > > > clock is specified in the correct order as documented by the binding. > > > Relying on 'pre-OF' code for a OF-only driver also seems > > > counter-intuitive. > > > > I do agree with those arguments. What I was saying is that for drivers > > which aren't DT only, of_clk_get() is not an option and that maybe > > others would be encouraged by the example to not use the generic APIs > > even if their driver could be used in non-DT setups. But maybe I'm > > worrying needlessly. > > > > That said, maybe somebody with a broader view of things like Arnd > > (Cc'ed) could share his thoughts. > > As I have already said, the way the DT bindings were done for the clk > stuff was wrong. A little thought put into it would've come up with > a much better solution which wouldn't have needed of_clk_get() at all. > > How? > > The arguments for clk_get() are: > 1. the struct device, which you can get the OF-node from. > 2. a _device_ _specific_ _clock_ _input_ _name_ (or NULL if there's only > one.) > > So, we have something that defines a hardware clock input name, which > can be used to generate a property name for OF. So, what _could_ have > been done is this: > > clock-<input-name> = <&provider-node clk-output-index>; > > where the property name is generated by: > > snprintf(prop, sizeof(prop), "clk-%s", name ? name : "default");
But we already have this, only with slightly different syntax:
clocks = <&provider foo-index>, <&provider bar-index>; clock-names = "foo", "bar";
> So I continue to assert that our current design is wrong - and it will > cause driver authors to pointlessly have to make a choice at every stage > between DT and non-DT based systems.
I think the reason that Tony brought this up is that with this API, the clock-names property becomes mandatory if you have more than one input clock.
Thierry [unhandled content-type:application/pgp-signature] | |