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 18:07:57 +0200 Message-ID: <50ACFC5D.1090406@ti.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alan Stern Cc: Felipe Balbi , keshava_mgowda-l0cyMroinI0@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andy Green List-Id: linux-omap@vger.kernel.org On 11/21/2012 05:32 PM, Alan Stern wrote: > On Wed, 21 Nov 2012, Roger Quadros wrote: > >> 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. > > Ah, okay. Then yes, assuming you want to power this chip only when > either ehci-hcd or the ethernet driver is loaded, the right places > to manage the power GPIO are in the init and exit routines of the two > drivers. > The Ethernet function actually connects over USB within the chip. So managing the power only in the ehci-hcd driver should suffice. cheers, -roger -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html