From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roger Quadros Subject: Re: [PATCH 16/16] ARM: OMAP: omap4panda: Power down the USB PHY and ETH when not in use Date: Wed, 21 Nov 2012 17:13:41 +0200 Message-ID: <50ACEFA5.4080104@ti.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from devils.ext.ti.com ([198.47.26.153]:47774 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755070Ab2KUPNo (ORCPT ); Wed, 21 Nov 2012 10:13:44 -0500 In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Alan Stern Cc: Felipe Balbi , keshava_mgowda@ti.com, linux-usb@vger.kernel.org, linux-omap@vger.kernel.org, Andy Green On 11/21/2012 04:52 PM, Alan Stern wrote: > On Wed, 21 Nov 2012, Felipe Balbi wrote: > >> On Thu, Nov 15, 2012 at 04:34:14PM +0200, Roger Quadros wrote: >>> From: Andy Green >>> >>> This patch changes the management of the two GPIO for >>> "hub reset" (actually controls enable of ULPI PHY and hub reset) and >>> "hub power" (controls power to hub + eth). >> >> looks like this should be done by the hub driver. Alan, what would you >> say ? Should the hub driver know how to power itself up ? > > Not knowing the context, I'm a little confused. What is this hub > you're talking about? Is it a separate USB hub incorporated into the > IP (like Intel's "rate-matching" hubs in their later chipsets)? Or is > it the root hub? > This is actually a USB HUB + Ethernet combo chip (LAN9514) that is hard wired on the panda board with its Power and Reset pins controlled by 2 GPIOs from the OMAP SoC. When powered, this chip can consume significant power (~0.7 W) because of the (integrated Ethernet even when suspended. I suppose the ethernet driver SMSC95XX) doesn't put it into a low enough power state on suspend. It doesn't make sense to power the chip when USB is not required on the whole (e.g. ehci_hcd module is not loaded). This is what this patch is trying to fix. cheers, -roger