linux-kernel - Re: [PATCH v2 3/5] extcon: arizona: Convert to gpiod

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Message-ID: <20150619095434.GV32730@opensource.wolfsonmicro.com>
Date:	Fri, 19 Jun 2015 10:54:34 +0100
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	cw00.choi@...sung.com
Cc:	Lee Jones <lee.jones@...aro.org>,
	"myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	devicetree <devicetree@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	patches@...nsource.wolfsonmicro.com
Subject: Re: [PATCH v2 3/5] extcon: arizona: Convert to gpiod

On Fri, Jun 19, 2015 at 06:50:03PM +0900, Chanwoo Choi wrote:
> On Fri, Jun 19, 2015 at 6:13 PM, Charles Keepax
> <ckeepax@...nsource.wolfsonmicro.com> wrote:
> > On Fri, Jun 19, 2015 at 05:39:22PM +0900, Chanwoo Choi wrote:
> >> On Fri, Jun 19, 2015 at 5:14 PM, Charles Keepax
> >> <ckeepax@...nsource.wolfsonmicro.com> wrote:
> >> > On Fri, Jun 19, 2015 at 11:36:47AM +0900, Chanwoo Choi wrote:
> >> >> Hi Charles,
> >> >>
> >> >> On Thu, Jun 18, 2015 at 11:43 PM, Charles Keepax
> >> >> <ckeepax@...nsource.wolfsonmicro.com> wrote:
> >> >> > Convert to using the newer gpiod interface for the micd_pol_gpio.
> >> >> > Although we still carry support for the old gpio interface from pdata.
> >> >> >
> >> >> > Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> >> >> > ---
> >> >> > +                       mode = GPIOD_OUT_HIGH;
> >> >> > +               else
> >> >> > +                       mode = GPIOD_OUT_LOW;
> >> >> > +
> >> >> > +               info->micd_pol_gpio = gpiod_get_optional(arizona->dev,
> >> >> > +                                                        "wlf,micd-pol",
> >> >> > +                                                        GPIOD_OUT_LOW);
> >> >>
> >> >> You can use the devm_gpiod_get_optional() to manage the system
> >> >> resource automatically.
> >> >>
> >> >
> >> > We can't actually use the devm call here, we need to pass
> >> > arizona->dev as that is where the DT will reside, which is the
> >> > device for the MFD. But if the devm is attached to the device for
> >> > the MFD then it will not clear up when the extcon driver is
> >> > unloaded. As such we have to do the put manually.
> >> >
> >> > I will look at respinning for the other comments.
> >>
> >> I don't understand. extcon-arizona.c used already following devm_* functions:
> >> - devm_kzalloc()
> >> - devm_regulator_get()
> >> - devm_extcon_dev_*()
> >> - devm_input_allocate_device()
> >> - devm_gpio_request_one()
> >
> > Yes but if you look at those all of those are against &pdev->dev
> > which is the extcon device.
> >
> > The gpiod interface expects the device passed to both contain
> > the of_node and be used for the devm operations. But we need to
> > use the extcon device for the devm operations, but the of_node is
> > contained on the MFD device.
> >
> > So if I do:
> >
> > devm_gpiod_get_optional(arizona->dev, ....
> >
> > Then the gpiod won't be released when the extcon device is
> > removed. But if I do:
> >
> > devm_gpiod_get_optional(&pdev->dev, ....
> >
> > Then it won't be able to find the DT entries.
> 
> I understand the difference between arizona->dev and &pdev->dev.
> 
> But, extcon-arizona.c already get the instance of regulator by using
> devm_regulator_get() with &pdev->dev as following:
> The devm_regulator_get() can find the DT entry in dts file.
>                  info->micvdd = devm_regulator_get(&pdev-dev, "MICVDD");
> 
> How did extcon-arizona.c get the instance of regulator throught
> devm_regulator_get() in dts file?

The regulator API contains a feature called regulator aliases,
(see regulator_register_supply_alias) which the MFD driver for
Arizona registers a bunch of. So when the regulator lookup is
done the regulator core will actually do the lookup on the
parent MFD device rather than on the extcon device.

Thanks,
Charles
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