linux-kernel - Re: [PATCH v6 0/4] Runtime Interpreted Power Sequences

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Date:	Thu, 13 Sep 2012 09:24:53 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Alex Courbot <acourbot@...dia.com>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	Stephen Warren <swarren@...dia.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Leela Krishna Amudala <l.krishna@...sung.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Anton Vorontsov <cbou@...l.ru>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH v6 0/4] Runtime Interpreted Power Sequences

On 09/13/2012 01:29 AM, Mark Brown wrote:
> On Thu, Sep 13, 2012 at 04:26:34PM +0900, Alex Courbot wrote:
>> On Thursday 13 September 2012 15:19:30 Mark Brown wrote:
>>>> On Thursday 13 September 2012 14:25:53 Mark Brown wrote:
>>>>> It would be sensible to make sure that the framework is done in such a
>>>>> way that drivers can use it - there will be drivers (perhaps not display
>>>>> ones) that have a known power sequence and which could benefit from the
>>>>> ability to use library code to implement it based on the user simply
>>>>> supplying named resources.
> 
>>>> Not sure I understand what you mean, but things should be working this way
>>>> already - regulators and PWMs are acquired by name using the standard
>>>> regulator_get() and pwm_get() functions. GPIOs do not, AFAIK, have a way
>>>> to be referenced by name so their number is used instead.
> 
>>> Right, but the sequencing for enabling them is currently open coded in
>>> each driver.
> 
>> Mmm then I'm afraid I don't see what you wanted to say initially - could you 
>> elaborate?
> 
> The driver knows the power sequence.  Having to type the same sequence
> into the DT or platform data for each board using the device wouuld be
> retarded so we need the drivers to be able to give the sequence to the
> library if they're going to be able to reuse it (which is a lot of what
> Tomi is talking about).

I believe that's trivial to implement. The relevant function is:

struct power_seq_set *devm_power_seq_set_build(struct device *dev,
		   struct platform_power_seq_set *pseq);

It's up to the driver whether pseq comes from platform data or is
hard-coded into the driver (or not provided at all, for the DT case).
So, the only change needed to convert a "hard-coded" driver to this API
is to convert the current custom data structure (or code) that describes
the sequence into a struct platform_power_seq_set.
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