From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757581Ab3BKPbX (ORCPT ); Mon, 11 Feb 2013 10:31:23 -0500 Received: from service87.mimecast.com ([91.220.42.44]:48408 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756758Ab3BKPbW convert rfc822-to-8bit (ORCPT ); Mon, 11 Feb 2013 10:31:22 -0500 Date: Mon, 11 Feb 2013 15:31:13 +0000 From: Mark Rutland To: Roger Quadros Cc: "tony@atomide.com" , "b-cousson@ti.com" , "balbi@ti.com" , "gregkh@linuxfoundation.org" , "stern@rowland.harvard.edu" , "linux@arm.linux.org.uk" , "kishon@ti.com" , "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2 01/14] usb: phy: nop: Add device tree support and binding information Message-ID: <20130211153112.GA15013@e106331-lin.cambridge.arm.com> References: <1360252974-7912-1-git-send-email-rogerq@ti.com> <1360252974-7912-2-git-send-email-rogerq@ti.com> <20130211114040.GA2726@e106331-lin.cambridge.arm.com> <51190AD2.3030006@ti.com> MIME-Version: 1.0 In-Reply-To: <51190AD2.3030006@ti.com> User-Agent: Mutt/1.5.20 (2009-06-14) X-OriginalArrivalTime: 11 Feb 2013 15:31:17.0055 (UTC) FILETIME=[D56DB4F0:01CE086C] X-MC-Unique: 113021115312000301 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Roger, On Mon, Feb 11, 2013 at 03:14:26PM +0000, Roger Quadros wrote: > On 02/11/2013 01:40 PM, Mark Rutland wrote: > > Hello, > > > > On Thu, Feb 07, 2013 at 04:02:41PM +0000, Roger Quadros wrote: > >> The PHY clock, clock rate, VCC regulator and RESET regulator > >> can now be provided via device tree. > >> > >> Signed-off-by: Roger Quadros > >> Acked-by: Felipe Balbi > >> --- > >> .../devicetree/bindings/usb/usb-nop-xceiv.txt | 34 ++++++++++++++++++ > >> drivers/usb/otg/nop-usb-xceiv.c | 36 +++++++++++++++---- > >> 2 files changed, 62 insertions(+), 8 deletions(-) > >> create mode 100644 Documentation/devicetree/bindings/usb/usb-nop-xceiv.txt > >> > >> diff --git a/Documentation/devicetree/bindings/usb/usb-nop-xceiv.txt b/Documentation/devicetree/bindings/usb/usb-nop-xceiv.txt > >> new file mode 100644 > >> index 0000000..d7e2726 > >> --- /dev/null > >> +++ b/Documentation/devicetree/bindings/usb/usb-nop-xceiv.txt > >> @@ -0,0 +1,34 @@ > >> +USB NOP PHY > >> + > >> +Required properties: > >> +- compatible: should be usb-nop-xceiv > > > > This might be better as "linux,usb-no-xceiv", given this is a Linux-specific > > 'device'. > > > > Saying that, I'm not sure I understand why this device needs to be instantiated > > from devicetree. As I understand it from looking at the driver, it's purely a > > Linux implementation detail used in the case of autonomous PHYs, and not an > > actual piece of hardware or firmware system. I must admit to being unfamiliar > > with this area of hardware, have I misunderstood somethign here? > > The PHY is a physical device and may need resources like power and clock to be functional. > The only reason that driver is named NOP is that many USB controllers know how to talk to > the standard PHYs and don't need any interface/management software. Ok. That makes sense. Apologies for the noise. > > The PHY driver you are looking at most likely doesn't have the recent changes I wrote to > manage the PHY clock/reset/power. i.e. patches 3, 4 and 5 in the series > https://lkml.org/lkml/2013/1/28/275 > > Before this, the ehci-omap driver was trying to manage the PHY power and reset, which was > wrong. Yes. That makes a lot more sense now. Thanks for the info! Thanks, Mark.