linux-kernel - Re: [PATCH 4/5] ARM: dts: imx6sx-sabreauto: add fec support

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Message-ID: <20180504084508.GD3443@dragon>
Date:   Fri, 4 May 2018 16:45:09 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Anson Huang <anson.huang@....com>
Cc:     Fabio Estevam <festevam@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Andy Duan <fugang.duan@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 4/5] ARM: dts: imx6sx-sabreauto: add fec support

On Thu, Apr 26, 2018 at 06:57:07AM +0000, Anson Huang wrote:
> > > Sorry, I made a mistake here, the MAX7320 IO0 is for adjusting FEC1's
> > > voltage,
> > 
> > In this case you need to pass the 'phy-supply' property inside the fec node and
> > add a regulator that is controlled via MAX7320 IO0 pin.
> 
> The 'phy-supply' is for enabling/disabling phy regulator, but here the MAX7322 IO0 is NOT for
> enabling/disabling PHY regulator, it is for IO voltage switch between 1.5V and 1.8V, our ENET
> IO can work with both 1.5V and 1.8V, so any config is OK for ENET function.
> 
> The 1.5V/1.8V selection is a one time setting thing, that means we only need to
> config it once during boot up, most of i.MX platforms does NOT provide such voltage
> switch function for ENET IO, on this 6SX sabre auto board, it is more like a backup or
> validation purpose. With default settings, ENET's function is NOT impacted at all.
> 
> I think we can add a gpio regulator for it and let the regulator initialization set the GPIO
> Level for fec, such below, with " enable-active-high " present, GPIO will be at LOW and voltage
> is 1.5V, without this property, GPIO will be HIGH and voltage will be 1.8V.
> +               reg_fec: fec_io_supply {
> +                       compatible = "regulator-gpio";
> +                       regulator-name = "1.8V_1.5V_FEC";
> +                       regulator-min-microvolt = <1500000>;
> +                       regulator-max-microvolt = <1800000>;
> +                       states = <1500000 0x0 1800000 0x1>;
> +                       enable-gpio = <&max7322 0 GPIO_ACTIVE_HIGH>;
> +                       vin-supply = <&sw2_reg>;
> +                       enable-active-high;
> +               };

Looking at gpio-regulator bindings doc, I feel that property 'gpios'
rather than 'enable-gpio' should be used to specify the MAX7320 IO0 pin.

- enable-gpio           : GPIO to use to enable/disable the regulator.
- gpios                 : GPIO group used to control voltage.

Shawn