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

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Message-id: <1414579362.18868.11.camel@AMDC1943>
Date:	Wed, 29 Oct 2014 11:42:42 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
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>
Subject: Re: [PATCH 6/8] regulator: max77686: Add external GPIO control

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.

Best regards,
Krzysztof

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