linux-kernel - Re: [RFC v5 07/15] usb: ehci: add vbus-gpio parameter

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Message-Id: <20160219011137.d8f85d72bbaa18c6e206dd09@gmail.com>
Date:	Fri, 19 Feb 2016 01:11:37 +0300
From:	Antony Pavlov <antonynpavlov@...il.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Marek Vasut <marex@...x.de>, linux-mips@...ux-mips.org,
	Wills Wang <wills.wang@...e.com>,
	Daniel Schwierzeck <daniel.schwierzeck@...il.com>,
	Alban Bedel <albeu@...e.fr>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v5 07/15] usb: ehci: add vbus-gpio parameter

On Thu, 18 Feb 2016 21:31:20 +0300
Sergei Shtylyov <sergei.shtylyov@...entembedded.com> wrote:

> On 02/18/2016 09:06 PM, Antony Pavlov wrote:
[...]
> > so I use regulator in the TL-MR3020 board dts file:
> >
> >          reg_usb_vbus: reg_usb_vbus {
> >                  compatible = "regulator-fixed";
> >                  regulator-name = "usb_vbus";
> >                  regulator-min-microvolt = <5000000>;
> 
>     Not 0?
> 
> >                  regulator-max-microvolt = <5000000>;
> >                  gpio = <&gpio 8 GPIO_ACTIVE_HIGH>;
> 
>     Where's the switch if both voltages are equal?

Here is a quote from linux/Documentation/devicetree/bindings/regulator/fixed-regulator.txt

        Any property defined as part of the core regulator
        binding, defined in regulator.txt, can also be used.
        However a fixed voltage regulator is expected to have the
        regulator-min-microvolt and regulator-max-microvolt
        to be the same.

Moreover please see this of_get_fixed_voltage_config() code fragment
(please see linux/drivers/regulator/fixed.c for details):

	if (init_data->constraints.min_uV == init_data->constraints.max_uV) {
		config->microvolts = init_data->constraints.min_uV;
	} else {
		dev_err(dev,
			 "Fixed regulator specified with variable voltages\n");
		return ERR_PTR(-EINVAL);
	}

-- 
Best regards,
  Antony Pavlov