Messages in this thread | | | Date | Tue, 23 Oct 2012 10:31:28 +0100 | From | Russell King - ARM Linux <> | Subject | Re: [PATCH 2/3] PWM: vt8500: Update vt8500 PWM driver support |
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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");
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.
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