Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757399AbbGGO2y (ORCPT ); Tue, 7 Jul 2015 10:28:54 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:33345 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S932280AbbGGO2g (ORCPT ); Tue, 7 Jul 2015 10:28:36 -0400 Date: Tue, 7 Jul 2015 10:28:34 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Felipe Balbi cc: Douglas Anderson , Greg Kroah-Hartman , John Youn , , Chris Zhong , Heiko Stuebner , Julius Werner , Andrew Bresticker , Alexandru Stan , , , Subject: Re: [REPOST PATCH 3/3] USB: dwc2: Don't turn off the usbphy in suspend if wakeup is enabled In-Reply-To: <20150706190212.GN20779@saruman.tx.rr.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1646 Lines: 41 On Mon, 6 Jul 2015, Felipe Balbi wrote: > > You know, this is the first time I've run across this optimization. > > > > In principle it applies to any USB host controller, not just to PHYs. > > There's no reason to enable wakeup for a controller if none of the > > attached devices can issue a wakeup request. > > > > I don't know if implementing this in other HCDs would save any power. > > Any ideas? > > most likely it would. Enabling wakeup usually boils down to keeping a > tiny part of the controller (or PHY) powered up. Sometimes that lies in > an always-on power domain, so there would be no difference. Doug, how would you feel about reworking the patch that exports usb_wakeup_enabled_descendants()? Instead of doing it that way, create and export a new subroutine in hcd.c called usb_hcd_wakeup_not_needed(), or something similar. The idea is that a host controller driver can do something like this: do_wakeup = device_may_wakeup(...); if (usb_hcd_wakeup_not_needed(hcd)) do_wakeup = false; It encapsulates what you want in a form that can easily be used by every HCD. We can then add this call into the HCDs, over time. (Merging a change like this would be a challenge. I guess Felipe would have to put it in a separate branch which Greg could pull, or vice versa, so that the new routine would be available to patches submitted to either maintainer.) Alan Stern -- 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/