linux-kernel - Re: [PATCH 6/8] regulator: max77686: Add external GPIO control

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Message-ID: <5450C63B.3000602@collabora.co.uk>
Date:	Wed, 29 Oct 2014 11:49:31 +0100
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
CC:	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
	Ben Dooks <ben-linux@...ff.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, devicetree@...r.kernel.org,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH 6/8] regulator: max77686: Add external GPIO control

[adding Linus and Alexandre to the cc list]

Hello Krzysztof,

On 10/29/2014 11:42 AM, Krzysztof Kozlowski wrote:
> On wto, 2014-10-28 at 13:11 +0100, Krzysztof Kozlowski wrote:
>> On wto, 2014-10-28 at 09:52 +0100, Krzysztof Kozlowski wrote:
>> > On pon, 2014-10-27 at 21:03 +0100, Javier Martinez Canillas wrote:
>> > > Hello Krzysztof,
>> > > 
>> > > On 10/27/2014 04:03 PM, Krzysztof Kozlowski wrote:
>> > > > @@ -85,6 +91,9 @@ struct max77686_data {
>> > > >  	struct max77686_regulator_data *regulators;
>> > > >  	int num_regulators;
>> > > >  
>> > > > +	/* Array of size num_regulators with GPIOs for external control. */
>> > > > +	int *ext_control_gpio;
>> > > > +
>> > > 
>> > > The integer-based GPIO API is deprecated in favor of the descriptor-based GPIO
>> > > interface (Documentation/gpio/consumer.txt). Could you please use the later?
>> > 
>> > Sure, I can. Please have in mind that regulator core still accepts old
>> > GPIO so I will have to use desc_to_gpio(). That should work... and
>> > should be future-ready.
>> 
>> It seems I was too hasty... I think usage of the new gpiod API implies
>> completely different bindings.
>> 
>> The gpiod_get() gets GPIO from a device level, not from given sub-node
>> pointer. This means that you cannot have DTS like this:
>> ldo21_reg: ldo21 {
>> 	regulator-compatible = "LDO21";
>> 	regulator-name = "VTF_2.8V";
>> 	regulator-min-microvolt = <2800000>;
>> 	regulator-max-microvolt = <2800000>;
>> 	ec-gpio = <&gpy2 0 0>;
>> };
>> 
>> ldo22_reg: ldo22 {
>> 	regulator-compatible = "LDO22";
>> 	regulator-name = "VMEM_VDD_2.8V";
>> 	regulator-min-microvolt = <2800000>;
>> 	regulator-max-microvolt = <2800000>;
>> 	ec-gpio = <&gpk0 2 0>;
>> };
>> 
>> 
>> I could put GPIOs in device node:
>> 
>> max77686_pmic@09 {
>> 	compatible = "maxim,max77686";
>> 	interrupt-parent = <&gpx0>;
>> 	interrupts = <7 0>;
>> 	reg = <0x09>;
>> 	#clock-cells = <1>;
>> 	ldo21-gpio = <&gpy2 0 0>;
>> 	ldo22-gpio = <&gpk0 2 0>;
>> 
>> 	ldo21_reg: ldo21 {
>> 		regulator-compatible = "LDO21";
>> 		regulator-name = "VTF_2.8V";
>> 		regulator-min-microvolt = <2800000>;
>> 		regulator-max-microvolt = <2800000>;
>> 	};
>> 
>> 	ldo22_reg: ldo22 {
>> 		regulator-compatible = "LDO22";
>> 		regulator-name = "VMEM_VDD_2.8V";
>> 		regulator-min-microvolt = <2800000>;
>> 		regulator-max-microvolt = <2800000>;
>> 	};
>> 
>> This would work but I don't like it. The properties of a regulator are
>> above the node configuring that regulator.
>> 
>> Any ideas?
>> 
> 
> Continuing talking to myself... I found another problem - GPIO cannot be
> requested more than once (-EBUSY). In case of this driver (and board:
> Trats2) one GPIO is connected to regulators. The legacy GPIO API and
> regulator core handle this.
> 
> With new GPIO API I would have to implement some additional steps in
> such case...
> 
> So there are 2 issues:
> 1. Cannot put GPIO property in regulator node.
> 2. Cannot request some GPIO more than once.
> 
> I'm going back to legacy API for now.
> 

I've added the GPIO maintainers as cc so hopefully they can comment on this.

> Best regards,
> Krzysztof
> 

Best regards,
Javier
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