linux-kernel - Re: [PATCH 01/13] clk: tegra: Add binding for the Tegra124 DFLL clocksource

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Date:	Fri, 11 Jul 2014 20:21:27 +0300
From:	Tuomas Tynkkynen <ttynkkynen@...dia.com>
To:	Andrew Bresticker <abrestic@...omium.org>
CC:	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Peter De Schrijver <pdeschrijver@...dia.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH 01/13] clk: tegra: Add binding for the Tegra124 DFLL clocksource



On 11/07/14 20:08, Andrew Bresticker wrote:
> On Fri, Jul 11, 2014 at 9:48 AM, Tuomas Tynkkynen <ttynkkynen@...dia.com> wrote:
>>
>>
>> On 11/07/14 19:28, Andrew Bresticker wrote:
>>>
>>> On Thu, Jul 10, 2014 at 2:42 PM, Tuomas Tynkkynen <ttynkkynen@...dia.com>
>>> wrote:
>>>>
>>>> The DFLL is the main clocksource for the fast CPU cluster on Tegra124
>>>> and also provides automatic CPU rail voltage scaling as well. The DFLL
>>>> is a separate IP block from the usual Tegra124 clock-and-reset
>>>> controller, so it gets its own node in the device tree.
>>>
>>>
>>>> diff --git
>>>> a/Documentation/devicetree/bindings/clock/nvidia,tegra124-dfll.txt
>>>> b/Documentation/devicetree/bindings/clock/nvidia,tegra124-dfll.txt
>>>
>>>
>>>> +- nvidia,pmic-voltage-table: Array of 2-tuples.  Each entry should have
>>>> the
>>>> +  form <register-value voltage-in-uV>, indicating the register value
>>>> that
>>>> +  needs to be programmed to the PMIC for changing the VDD_CPU voltage to
>>>> +  the specified voltage. The table must be in ascending order by the
>>>> voltage.
>>>
>>>
>>> Instead of listing the register values for each voltage in the DT,
>>> can't you use regulator_list_voltage() to create this map?
>>>
>>
>> I don't see a way to get the register values that way, unless we assume that
>> the mapping is linear and doesn't have holes.
>
> Hmm... I guess if you don't assume it's linear and continuous you'd
> have to iterate over all 256 selectors.
>

I don't think we can assume that each selector maps to a concrete 
register value, though I'm not sure. include/linux/regulator/driver.h 
documents for @list_voltage "Selectors range from zero to one less 
regulator_desc.n_voltages." but maybe the consumer API could take 
different values.

-- 
nvpublic
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