Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754015AbbFMPAi (ORCPT ); Sat, 13 Jun 2015 11:00:38 -0400 Received: from netrider.rowland.org ([192.131.102.5]:48640 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753929AbbFMPAa (ORCPT ); Sat, 13 Jun 2015 11:00:30 -0400 Date: Sat, 13 Jun 2015 11:00:29 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Lu Baolu cc: Mathias Nyman , Greg Kroah-Hartman , , Subject: Re: [PATCH v2 1/1] usb: core: lpm: set lpm_capable for root hub device In-Reply-To: <1434180189-11698-1-git-send-email-baolu.lu@linux.intel.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: 2369 Lines: 60 On Sat, 13 Jun 2015, Lu Baolu wrote: > Commit 25cd2882e2fc ("usb/xhci: Change how we indicate a host supports > Link PM.") removed the code to set lpm_capable for USB 3.0 super-speed > root hub. The intention of that change was to avoid touching usb core > internal field, a.k.a. lpm_capable, and let usb core to set it by > checking U1 and U2 exit latency values in the descriptor. > > Usb core checks and sets lpm_capable in hub_port_init(). Unfortunately, > root hub is a special usb device as it has no parent. Hub_port_init() > will never be called for a root hub device. That means lpm_capable will > by no means be set for the root hub. As the result, lpm isn't functional > at all in Linux kernel. > > This patch add the code to check and set lpm_capable when registering a > root hub device. It could be back-ported to kernels as old as v3.15, > that contains the Commit 25cd2882e2fc ("usb/xhci: Change how we indicate > a host supports Link PM."). > > Cc: stable@vger.kernel.org # 3.15 > Reported-by: Kevin Strasser > Signed-off-by: Lu Baolu > --- > --- a/drivers/usb/core/usb.h > +++ b/drivers/usb/core/usb.h > @@ -82,6 +82,7 @@ extern int usb_runtime_suspend(struct device *dev); > extern int usb_runtime_resume(struct device *dev); > extern int usb_runtime_idle(struct device *dev); > extern int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable); > +extern int usb_device_supports_lpm(struct usb_device *udev); > > #else > > @@ -106,6 +107,11 @@ static inline int usb_set_usb2_hardware_lpm(struct usb_device *udev, int enable) > return 0; > } > > +static inline int usb_device_supports_lpm(struct usb_device *udev) > +{ > + return 0; > +} > + > #endif > > extern struct bus_type usb_bus_type; In fact, usb_device_supports_lpm() is compiled even when CONFIG_PM isn't set. Maybe this should be changed. But if you don't want to change it now, you need to put the declaration outside the "#ifdef CONFIG_PM" region. As it is, your patch is still broken (did you try building it with CONFIG_PM unset?). 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/