Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933054AbbGHUbv (ORCPT ); Wed, 8 Jul 2015 16:31:51 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:56224 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1758521AbbGHUbm (ORCPT ); Wed, 8 Jul 2015 16:31:42 -0400 Date: Wed, 8 Jul 2015 16:31:41 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: "Rafael J. Wysocki" cc: Tomeu Vizoso , "linux-pm@vger.kernel.org" , Laurent Pinchart , Dmitry Torokhov , Len Brown , Pavel Machek , Greg Kroah-Hartman , Ulf Hansson , Kevin Hilman , Russell King , Krzysztof Kozlowski , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3 2/2] PM / Runtime: Add pm_runtime_enable_recursive In-Reply-To: <9291571.JSDgNsKidJ@vostro.rjw.lan> 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: 5347 Lines: 115 On Wed, 8 Jul 2015, Rafael J. Wysocki wrote: > I seem to have lost the context here, sorry about that. > > The idea seems to be to rely on the fact that the RPM status for all devices > is initially RPM_SUSPENDED and that never changes if runtime PM is never > enabled for the device, so in that particular case it would be OK to treat > the "power.direct_complete set + RPM status == RPM_SUSPENDED" combination > as valid even though runtime PM has never been enabled for the device in > question (provided that power.direct_complete will never be set for "real" > devices that don't support runtime PM). Is that correct? I would have expressed it slightly differently, but yes, that's correct. > That seems to be fragile, but I have no strong opinion. In itself it's not all that bad, I think. In the presence of Tomeu's new direct_complete_default flag, however, it does seem quite fragile. We may want to do the direct_complete_default thing in a different way. For example, the PM core could automatically set the direct_complete flag if a device has _none_ of the system suspend callbacks (i.e., no prepare, suspend, suspend_late, suspend_noirq, resume_noirq, resume_early, resume, or complete). Although it would be a little awkward to check this, it would be safer than inheriting direct_complete_default from the parent and it ought to solve Tomeu's problem just as well. > Let's do that change if it allows us to make forward progress here. Please > feel free to submit a documentation patch along the lines you've suggested. Here's a proposed patch to illustrate what I have in mind. Since it removes the only usage of pm_runtime_suspended_if_enabled(), it also removes the definition of that function. Alan Stern Index: usb-4.1/drivers/base/power/main.c =================================================================== --- usb-4.1.orig/drivers/base/power/main.c +++ usb-4.1/drivers/base/power/main.c @@ -1374,7 +1374,7 @@ static int __device_suspend(struct devic if (dev->power.direct_complete) { if (pm_runtime_status_suspended(dev)) { pm_runtime_disable(dev); - if (pm_runtime_suspended_if_enabled(dev)) + if (pm_runtime_status_suspended(dev)) goto Complete; pm_runtime_enable(dev); Index: usb-4.1/Documentation/power/devices.txt =================================================================== --- usb-4.1.orig/Documentation/power/devices.txt +++ usb-4.1/Documentation/power/devices.txt @@ -341,6 +341,13 @@ the phases are: and is entirely responsible for bringing the device back to the functional state as appropriate. + Note that this direct-complete procedure applies even if the device is + disabled for runtime PM; only the runtime-PM status matters. It follows + that if a device has system-sleep callbacks but does not support runtime + PM, then its prepare callback must never return a positive value. This + is because all devices are initially set to runtime-suspended with + runtime PM disabled. + 2. The suspend methods should quiesce the device to stop it from performing I/O. They also may save the device registers and put it into the appropriate low-power state, depending on the bus type the device is on, Index: usb-4.1/Documentation/power/runtime_pm.txt =================================================================== --- usb-4.1.orig/Documentation/power/runtime_pm.txt +++ usb-4.1/Documentation/power/runtime_pm.txt @@ -445,10 +445,6 @@ drivers/base/power/runtime.c and include bool pm_runtime_status_suspended(struct device *dev); - return true if the device's runtime PM status is 'suspended' - bool pm_runtime_suspended_if_enabled(struct device *dev); - - return true if the device's runtime PM status is 'suspended' and its - 'power.disable_depth' field is equal to 1 - void pm_runtime_allow(struct device *dev); - set the power.runtime_auto flag for the device and decrease its usage counter (used by the /sys/devices/.../power/control interface to Index: usb-4.1/include/linux/pm_runtime.h =================================================================== --- usb-4.1.orig/include/linux/pm_runtime.h +++ usb-4.1/include/linux/pm_runtime.h @@ -98,11 +98,6 @@ static inline bool pm_runtime_status_sus return dev->power.runtime_status == RPM_SUSPENDED; } -static inline bool pm_runtime_suspended_if_enabled(struct device *dev) -{ - return pm_runtime_status_suspended(dev) && dev->power.disable_depth == 1; -} - static inline bool pm_runtime_enabled(struct device *dev) { return !dev->power.disable_depth; @@ -164,7 +159,6 @@ static inline void device_set_run_wake(s static inline bool pm_runtime_suspended(struct device *dev) { return false; } static inline bool pm_runtime_active(struct device *dev) { return true; } static inline bool pm_runtime_status_suspended(struct device *dev) { return false; } -static inline bool pm_runtime_suspended_if_enabled(struct device *dev) { return false; } static inline bool pm_runtime_enabled(struct device *dev) { return false; } static inline void pm_runtime_no_callbacks(struct device *dev) {} -- 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/