linux-kernel - Re: [PATCH 1/4] regulator: add set_voltage_time[

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Message-ID: <20110311152037.GL1760@opensource.wolfsonmicro.com>
Date:	Fri, 11 Mar 2011 15:20:37 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Linus Walleij <linus.walleij@...ricsson.com>,
	Liam Girdwood <lrg@...mlogic.co.uk>,
	linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH 1/4] regulator: add set_voltage_time[_sel]
 infrastructure

On Fri, Mar 11, 2011 at 03:45:39PM +0100, Linus Walleij wrote:
> On Fri, Mar 11, 2011 at 1:25 PM, Mark Brown

> +               /*
> +                * If we can't obtain the old selector there is not enough
> +                * info to call set_voltage_time_sel().
> +                */
> +               if (rdev->desc->ops->set_voltage_time_sel &&
> +                   rdev->desc->ops->get_voltage_sel) {
> +                       unsigned int old_selector = 0;
> +
> +                       ret = rdev->desc->ops->get_voltage_sel(rdev);
> +                       if (ret < 0)
> +                               return ret;
> +                       old_selector = ret;
> +                       delay = rdev->desc->ops->set_voltage_time_sel(rdev,
> +                                               old_selector, selector);
> +               }
> +

Hrm, right.  This means we can only support this for selector based
get_voltage().  That's probably fine, I think.

> > I also think we should be exporting this to consumers as things like
> > cpufreq are interested in the latency for voltage changes.

> Can we take that when we have a consumer that wants it? Looking
> at it it becomes rather complex, since consumers don't know the
> core-internal selectors, just discrete enumerated voltages, so these
> have to be mapped back to selectors etc, that's pretty much ovehead
> code that sits unused.

> (If you insist, I will implement it.)

Consumers know about the set of selectors as they are used to enumerate
the supported voltages via list_voltage().  An existing cpufreq driver
such as the s3c64xx one would be able to take advantage of this very
quickly.
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