linux-kernel - Re: [PATCH v2 2/2] regulator: add device tree support for max8997

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Message-id: <4F1FEF55.8030604@samsung.com>
Date:	Wed, 25 Jan 2012 13:02:29 +0100
From:	Karol Lewandowski <k.lewandowsk@...sung.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Thomas Abraham <thomas.abraham@...aro.org>
Cc:	linux-kernel@...r.kernel.org, rpurdie@...ys.net,
	rob.herring@...xeda.com, grant.likely@...retlab.ca,
	kgene.kim@...sung.com, myungjoo.ham@...sung.com,
	kyungmin.park@...sung.com, dg77.kim@...sung.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, Rajendra Nayak <rnayak@...com>
Subject: Re: [PATCH v2 2/2] regulator: add device tree support for max8997

On 25.01.2012 12:26, Mark Brown wrote:
> On Wed, Jan 25, 2012 at 10:55:49AM +0100, Karol Lewandowski wrote:
>> On 12.01.2012 08:35, Thomas Abraham wrote:
>>> Add device tree based discovery support for max8997.
>>
>>> +	pdata->regulators = rdata;
>>> +	for_each_child_of_node(regulators_np, reg_np) {
>>> +		for (i = 0; i<   ARRAY_SIZE(regulators); i++)
>>> +			if (!of_node_cmp(reg_np->name, regulators[i].name))
>>> +				break;
>>> +		rdata->id = i;
>>> +		rdata->initdata = of_get_regulator_init_data(
>>> +						iodev->dev, reg_np);
>
>> One more thing - of_get_regulator_init_data() will set apply_uV to 1
>> so we need to reset it for BUCK6, which doesn't provide
>> set_voltage() ops, like:
>
>> 	if (rdata->initdata&&  regulators[i].id == MAX8997_BUCK6)
>> 		rdata->initdata->constraints.apply_uV = 0;
>
> So, over in the other thready you were referring to mailing list posts
> you made in the past few moments as examples of past issues.  Please at
> least mention that there hasn't been any actual discussion when doing
> this...

Sorry if this caused confusion.  I'll be more cautious next time.

> I don't see a problem here, if the device can't set the voltage then
> setting constraints to allow the voltage to be changed is silly and the
> user just shouldn't do that.

Agreed.  I've assumed that old platform code done right thing when it 
set buck6 voltage constraints [1].

However, I still find it little problematic that dt and non-dt versions 
behave differently when given the same set of parameters (previously 
apply_uV wasn't the default and required explicit flag).


Thomas, would you mind adding small note to pmic's bindings 
documentation stating that Buck6 is basically on/off switch? (Thus, no 
voltage should nor can be specified).

[1] http://lxr.linux.no/linux+v3.2.1/arch/arm/mach-exynos/mach-nuri.c#L802

Regards,
-- 
Karol Lewandowski | Samsung Poland R&D Center | Linux/Platform
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