Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753546Ab3H0SyI (ORCPT ); Tue, 27 Aug 2013 14:54:08 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:37577 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752355Ab3H0SyG (ORCPT ); Tue, 27 Aug 2013 14:54:06 -0400 Date: Tue, 27 Aug 2013 13:53:29 -0500 From: Felipe Balbi To: Mark Rutland CC: Felipe Balbi , Kumar Gala , "rob.herring@calxeda.com" , Pawel Moll , Stephen Warren , Ian Campbell , "devicetree@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] usb: dwc3: core: clarify usb-phy array binding Message-ID: <20130827185329.GT3005@radagast> Reply-To: References: <1376062832-23288-1-git-send-email-galak@codeaurora.org> <20130809162848.GW27325@e106331-lin.cambridge.arm.com> <1A03353A-9299-4D73-9786-4ECBC1DD4E05@codeaurora.org> <20130812180553.GD27954@radagast> <20130813133410.GO27165@e106331-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="HBIh8aIvd1vDZWkD" Content-Disposition: inline In-Reply-To: <20130813133410.GO27165@e106331-lin.cambridge.arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4245 Lines: 101 --HBIh8aIvd1vDZWkD Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Tue, Aug 13, 2013 at 02:34:10PM +0100, Mark Rutland wrote: > On Mon, Aug 12, 2013 at 07:05:53PM +0100, Felipe Balbi wrote: > > On Fri, Aug 09, 2013 at 01:42:15PM -0500, Kumar Gala wrote: > > >=20 > > > On Aug 9, 2013, at 11:28 AM, Mark Rutland wrote: > > >=20 > > > > On Fri, Aug 09, 2013 at 04:40:32PM +0100, Kumar Gala wrote: > > > >> The binding spec wasn't clear that the order of the phandles in the > > > >> usb-phy array has meaning. Clarify this point in the binding that > > > >> it should be . > > > >>=20 > > > >> Signed-off-by: Kumar Gala > > > >> --- > > > >> Documentation/devicetree/bindings/usb/dwc3.txt | 4 +++- > > > >> 1 file changed, 3 insertions(+), 1 deletion(-) > > > >>=20 > > > >> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Docu= mentation/devicetree/bindings/usb/dwc3.txt > > > >> index 7a95c65..8a9770b 100644 > > > >> --- a/Documentation/devicetree/bindings/usb/dwc3.txt > > > >> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt > > > >> @@ -6,7 +6,9 @@ Required properties: > > > >> - compatible: must be "synopsys,dwc3" > > > >> - reg : Address and length of the register set for the device > > > >> - interrupts: Interrupts used by the dwc3 controller. > > > >> - - usb-phy : array of phandle for the PHY device > > > >> + - usb-phy : array of phandle for the PHY device. The first elem= ent > > > >> + in the array is expected to be a handle to the USB2/HS PHY and > > > >> + the second element is expected to be a handle to the USB3/SS P= HY > > > >=20 > > > > Just to check - it's not valid to have a USB3 phy without a USB2 ph= y? > > >=20 > > > Don't know, hopefully Felipe will chime in on that. > >=20 > > that'd be a really non-standard implementation. Per-spec, USB3 is > > *always* backwards compatible with USB2. >=20 > I'm slightly confused here. From a quick look at the driver, it expects > two separate phys to be present -- one handling only USB2, and one > handling USB3 (with USB2 backwards compatibility). >=20 > So it's not physically possible for someone to just wire up a single phy > to the device, either USB2-only or USB3? of course it is :-) In fact, TI has done it. But it causes a whole bunch of other problems to support that sort of model. For one, in some systems, a clock generated by the USB3 PHY is backfed into the IP and if USB3 PHY isn't running, the dwc3 IP won't start. I even wrote a patch making USB3 PHY optional, but didn't push it exactly because it broke some other systems and I can't guarantee users won't mess up their DTS/pdata. > You can describe the USB2-only case in the dt by only listing the first > phy (though the driver won't support it as it expects both to be > present), but it's impossible to describe that you've wired up a single > phy that's USB3 capable. you might be right there... --=20 balbi --HBIh8aIvd1vDZWkD Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJSHPWpAAoJEIaOsuA1yqREyn8QALOcf71vhEBNM4k7VoHYQWWw 15VgvCrbaYPu/iFinRGWI+FPOUoJQ+w/1DdAH+N80hEYKHcqg7w6PjbAzhW0hDQL LNyWaq0jl4N84aRghCngdObZc3WwZqwFb/wDHjxMWSA0fNdqs9/bn9baahyH5+He OrMfMAu+J4xEQO5C6i63/PCO7X7GwFA4nPu3qXhG8ncyBs+jWwdz2n933l8w6+sj pxo5GG5T6o8+HUuNlyfha8Ye4rUmMBYZy/1j24POOTIYppX394U0mfiJleQWTI6e WklNpz7lJUA7b32F8YDQB6El4sL7xlFe7yTh0m2NFEqfvTDsb6yc+3kQ5n0lE+/4 JJkDi4NICRGZdDxRQmUVLcIRUzLbqIXvV6Lj6T8+YeOeeek35f99/SR9+UHXLdpM 1s4rq6UZlfH1rsUeY2st+t0LPgZCrTGbhuUGhWkk1ZQfqa6Ig2Km1mmQQOo5Z9IP 0pKLgCt2oVnjm3uKobIzGsqCqmbV1Eu98xHPvlRpae/ikoBjsIz04rfy5K+DngjJ 28AVenyt8SfjONJwAuPXfDGypQDQp3eZTuc2NaDXd7KBEDnMbNqgSTqzwmSZ3AeB aE29RsF2f8hSGkI3fv8V1XTQuvKTVZ4rdf+TTOagIMpVCIqYJqjCos348QmsuVOv ncjyYo1N3P8Rcipw6I4z =zVOg -----END PGP SIGNATURE----- --HBIh8aIvd1vDZWkD-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/