From: David Cohen <david.a.cohen@linux.intel.com>
To: Linus Walleij <linus.walleij@linaro.org>,
Robert Baldyga <r.baldyga@samsung.com>,
heikki.krogerus@linux.intel.com
Cc: MyungJoo Ham <myungjoo.ham@samsung.com>,
Chanwoo Choi <cw00.choi@samsung.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
baolu.lu@linux.intel.com, balbi@ti.com
Subject: Re: [PATCH v2] extcon: otg_gpio: add driver for USB OTG port controlled by GPIO(s)
Date: Fri, 20 Feb 2015 11:17:00 -0800 [thread overview]
Message-ID: <20150220191700.GB15303@psi-dev26.jf.intel.com> (raw)
In-Reply-To: <CACRpkdYkcjgvYQBuGtu2-JGvtM+y-zrMD=0xyiZLS=b3gEGMOw@mail.gmail.com>
Hi Linus and Robert,
CC'ing Heikki as it involves a RFC from him.
On Fri, Feb 20, 2015 at 10:53:44AM +0100, Linus Walleij wrote:
> On Fri, Feb 20, 2015 at 7:41 AM, Robert Baldyga <r.baldyga@samsung.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.
I agree. But please, see below.
>
> 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?
Felipe suggested to "divide to conquer" instead of having a single
extcon driver to handle all these functions:
- The mux functions would be controlled by a possible new pinctrl-gpio
driver (Linus, your input here would be nice :)
- The VBUS would be a fixed regulator
- The USB ID would make usage of existent extcon-gpio
But the on fw side, this is a single ACPI device representing a virtual
device for USB OTG port, which is nothing but a bunch of independent
GPIOs.
I could make a mfd driver to register devices for those simpler and more
generic drivers, but according to [1] community recognized it as a hack
with ACPI since I'd need to give them the GPIO without requesting on
mfd.
I'm open for suggestions :)
Br, David
[1] https://lkml.org/lkml/2014/12/18/82
>
> Yours,
> Linus Walleij
next prev parent reply other threads:[~2015-02-20 19:15 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-22 22:43 [RFC/PATCH] extcon: otg_gpio: add driver for USB OTG port controlled by GPIO(s) David Cohen
2014-12-23 1:25 ` Peter Chen
2014-12-23 19:40 ` David Cohen
2014-12-24 3:08 ` Peter Chen
2014-12-24 22:46 ` David Cohen
2014-12-23 13:10 ` Sergei Shtylyov
2014-12-23 19:57 ` David Cohen
2014-12-23 20:09 ` Sergei Shtylyov
2014-12-23 20:43 ` David Cohen
2014-12-24 0:29 ` Felipe Balbi
2014-12-24 22:43 ` David Cohen
2014-12-26 4:49 ` Felipe Balbi
2015-02-17 19:18 ` David Cohen
2015-02-17 19:25 ` Felipe Balbi
2015-02-17 19:35 ` David Cohen
2015-02-18 10:17 ` Mika Westerberg
2015-02-18 17:53 ` David Cohen
2015-01-08 19:23 ` Linus Walleij
2015-02-17 19:20 ` David Cohen
2015-02-19 19:59 ` [PATCH v2] " David Cohen
2015-02-19 22:39 ` Paul Bolle
2015-02-20 19:02 ` David Cohen
2015-02-20 19:09 ` Felipe Balbi
2015-02-20 19:18 ` David Cohen
2015-02-20 19:10 ` Paul Bolle
2015-02-20 19:18 ` David Cohen
2015-02-20 6:41 ` Robert Baldyga
2015-02-20 9:53 ` Linus Walleij
2015-02-20 19:17 ` David Cohen [this message]
2015-02-20 19:36 ` Felipe Balbi
2015-02-20 19:59 ` David Cohen
2015-02-20 20:00 ` Felipe Balbi
2015-02-20 20:40 ` David Cohen
2015-03-07 20:03 ` Linus Walleij
2015-02-24 19:18 ` David Cohen
2015-03-07 20:06 ` Linus Walleij
2015-03-09 16:16 ` Felipe Balbi
2015-03-09 19:10 ` David Cohen
2015-03-16 16:46 ` David Cohen
2015-03-16 16:46 ` David Cohen
2015-03-19 8:18 ` Linus Walleij
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