linux-kernel - Re: [PATCH v2] extcon: otg_gpio: add driver for USB OTG port controlled by GPIO(s)

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Date:	Fri, 20 Feb 2015 10:53:44 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Robert Baldyga <r.baldyga@...sung.com>
Cc:	David Cohen <david.a.cohen@...ux.intel.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	baolu.lu@...ux.intel.com
Subject: Re: [PATCH v2] extcon: otg_gpio: add driver for USB OTG port
 controlled by GPIO(s)

On Fri, Feb 20, 2015 at 7:41 AM, Robert Baldyga <r.baldyga@...sung.com> wrote:
> Hi David,
>
> On 02/19/2015 08:59 PM, David Cohen wrote:
>> Some Intel platforms have an USB OTG port fully (or partially)
>> controlled by GPIOs:
>>
>> (1) USB ID is connected directly to a pulled up GPIO.
>>
>> Optionally:
>> (2) VBUS is enabled/disabled by a GPIO
>> (3) Platform has 2 USB controllers connected to same port: one for
>>     device and one for host role. D+/- are switched between phys.
>>     according to this GPIO level.
>>
>> This driver configures USB OTG port for device or host role according to
>> USB ID value.
>>  - If USB ID's GPIO level is low, OTG port is configured for host role
>>    by sourcing VBUS and switching D+/- to host phy.
>>  - If USB ID's GPIO level is high, by standard, the OTG port is
>>    configured for device role by not sourcing VBUS and switching D+/- to
>>    device controller.
>
> IMO it's not very elegant to handle VBUS power on/off in extcon driver.
> Creating fixed regulator would allow to make VBUS handling more generic.

IMHO it's just layers of abstraction piled on top of each other here.

I would put this adjacent to the phy driver somewhere in drivers/usb/*
and make the actual USB-driver thing handle its GPIOs directly.
But I guess David and Felipe have already discussed that as we're
seeing this patch?

Yours,
Linus Walleij
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