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Date: Thu, 30 Oct 2014 16:03:06 +0100
From: Krzysztof Kozlowski <k.kozlowski@...sung.com>
To: Alexandre Courbot <gnurou@...il.com>
Cc: Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
Samuel Ortiz <sameo@...ux.intel.com>,
Lee Jones <lee.jones@...aro.org>,
Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Linux Kernel Mailing List <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-arm-kernel@...ts.infradead.org>,
"linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>,
"devicetree@...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>
Subject: Re: [PATCH 6/8] regulator: max77686: Add external GPIO control
On czw, 2014-10-30 at 22:56 +0900, Alexandre Courbot wrote:
> Hi, and thanks for bringing this issue to us!
>
> On Wed, Oct 29, 2014 at 7:49 PM, Javier Martinez Canillas
> <javier.martinez@...labora.co.uk> wrote:
> > [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.
>
> For this problem you will probably want to use the
> dev(m)_get_named_gpiod_from_child() function from the following patch:
>
> https://lkml.org/lkml/2014/10/6/529
>
> It should reach -next soon now.
Thanks! Probably I would switch to "top" level gpios property anyway
(other reasons) but it would be valuable in some cases to specify them
per child node.
>
> >> 2. Cannot request some GPIO more than once.
>
> We have been confronted to this problem with the regulator core as well:
>
> http://marc.info/?l=linux-arm-kernel&m=140417649119733&w=1
>
> I have a draft patch that allows GPIOs to be requested by several
> clients. What prevented me from submitting it was that I wanted to
> make sure the different requested configurations were compatible, but
> maybe I am overthinking this. There are also a couple of other patches
> that this depends on (like removal of the big descs array), so I don't
> think it will be available too soon, sadly.
Shouldn't be the nature of get()/put() interface to allow multiple
requests? To me it was a kind of intuitive that I could do another
devm_gpiod_get() for the same gpio. But then it hit me with EBUSY :).
>
> So maybe your best shot for now is to keep using the integer API, as
> much as I hate it. Once we become able to request the same GPIO
> several times, you should be good to switch to descriptors. Sorry this
> has not been done faster.
I'll do it legacy way but I'll try to use bindings gpiolib-safe. This
way future transition in the driver should not affect bindings.
Best regards,
Krzysztof
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