Re: [RFC][PATCH v3 1/3] runtime interpreted power sequences

[Thierry Reding <thierry.reding@avionic-design.de>]

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On Thu, Aug 02, 2012 at 05:00:13PM +0900, Alex Courbot wrote:
> On 07/31/2012 07:45 AM, Stephen Warren wrote:
> >Oh I see. That's a little confusing. Why not just reference the relevant
> >resources directly in each step; something more like:
> >
> >		gpio@1 {
> >			action = "enable-gpio";
> >			gpio = <&gpio 1 0>;
> >		};
> >
> >I guess that might make parsing/building a little harder, since you'd
> >have to detect when you'd already done gpio_request() on a given GPIO
> >and not repeat it or something like that, but to me this makes the DT a
> >lot easier to comprehend.
> 
> I tried to move towards having the phandles directly in the
> sequences themselves - that reminded me why I did not do that in the
> first place. Let's say we have a sequence like this (reg property
> omitted on purpose):
> 
> 	power-on-sequence {
> 		step@0 {
> 			regulator = <&backlight_reg>;
> 			enable;
> 		};
> 		step@1 {
> 			delay = <10000>;
> 		};
> 		step@2 {
> 			pwm = <&pwm 2 5000000>;
> 			enable;
> 		};
> 		step@3 {
> 			gpio = <&gpio 28 0>;
> 			enable;
> 		};
> 	};
> 
> The problem is, how do we turn these phandles into the resource of
> interest. The type of the resource can be infered by the name of the
> property. The hard part is resolving the resource from the phandle -
> it seems like the API just does not allow to do this. GPIO has
> of_get_named_gpio, but AFAIK there are no equivalent for regulator
> consumer and PWM: the only way to use the DT with them is through
> get_regulator and get_pwm which work at the device level.
> 
> Or is there a way that I overlooked?

No, you are right. Perhaps we should add exported functions that do the
equivalent of of_pwm_request() or the regulator_dev_lookup() and
of_get_regulator() pair.

Thierry

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