Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965138AbbENTbI (ORCPT ); Thu, 14 May 2015 15:31:08 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:65416 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S964994AbbENTbG (ORCPT ); Thu, 14 May 2015 15:31:06 -0400 From: "Rafael J. Wysocki" To: Tomeu Vizoso Cc: linux-pm@vger.kernel.org, Alan Stern , Laurent Pinchart , Dmitry Torokhov , Kevin Hilman , Len Brown , Pavel Machek , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] PM / sleep: Let devices force direct_complete Date: Thu, 14 May 2015 21:56:18 +0200 Message-ID: <2929090.OdVc2hRah5@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.0.0+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1431610673-16801-1-git-send-email-tomeu.vizoso@collabora.com> References: <1431610673-16801-1-git-send-email-tomeu.vizoso@collabora.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5980 Lines: 145 On Thursday, May 14, 2015 03:37:52 PM Tomeu Vizoso wrote: > Introduce a new per-device flag power.force_direct_complete that will > instruct the PM core to let that device remain in runtime suspend when > the system goes into a sleep power state, regardless of the PM state of > any of its descendants. > > This is needed because otherwise it would be needed to get dozens of > drivers to implement the prepare() callback and be runtime PM active > even if they don't have a 1-to-1 relationship with a piece of HW. > > This only applies to devices that aren't wakeup-capable, as those would > need to setup their IRQs as wakeup-capable in their prepare() callbacks. > > Signed-off-by: Tomeu Vizoso Well, my idea of a "direct complete" flag was a bit different and I have a concern with this particular implementation. -> > > --- > > v2: * Fix wording as suggested by Kevin Hilman > --- > Documentation/power/runtime_pm.txt | 10 ++++++++++ > drivers/base/power/main.c | 14 ++++++++++---- > include/linux/pm.h | 1 + > 3 files changed, 21 insertions(+), 4 deletions(-) > > diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt > index 44fe1d2..e131aab 100644 > --- a/Documentation/power/runtime_pm.txt > +++ b/Documentation/power/runtime_pm.txt > @@ -665,6 +665,16 @@ as appropriate. This only applies to system suspend transitions that are not > related to hibernation (see Documentation/power/devices.txt for more > information). > > +For devices that know they can remain runtime suspended when the system > +transitions to a sleep state regardless of the PM state of their descendants, > +the flag power.force_direct_complete can be set on their device structures. > +This can be useful when a real device has several virtual devices as > +descendants and it would be very cumbersome to make sure that they return a > +positive value in their .prepare() callback and have runtime PM enabled. Usage > +of power.force_direct_complete is only allowed to devices that aren't > +wakeup-capable, as they would need to set their IRQs as wakeups in their > +.prepare() callbacks before the system transitions to a sleep state. > + > The PM core does its best to reduce the probability of race conditions between > the runtime PM and system suspend/resume (and hibernation) callbacks by carrying > out the following operations: > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index 3d874ec..7b962f5 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -1438,7 +1438,9 @@ static int __device_suspend(struct device *dev, pm_message_t state, bool async) > if (parent) { > spin_lock_irq(&parent->power.lock); > > - dev->parent->power.direct_complete = false; > + if (!dev->parent->power.force_direct_complete) > + dev->parent->power.direct_complete = false; > + > if (dev->power.wakeup_path > && !dev->parent->power.ignore_children) > dev->parent->power.wakeup_path = true; > @@ -1605,9 +1607,13 @@ static int device_prepare(struct device *dev, pm_message_t state) > * will do the same thing with all of its descendants". This only > * applies to suspend transitions, however. > */ > - spin_lock_irq(&dev->power.lock); > - dev->power.direct_complete = ret > 0 && state.event == PM_EVENT_SUSPEND; > - spin_unlock_irq(&dev->power.lock); > + if (state.event == PM_EVENT_SUSPEND) { > + spin_lock_irq(&dev->power.lock); > + dev->power.direct_complete = ret > 0 || > + (dev->power.force_direct_complete && > + !device_can_wakeup(dev)); -> What if the bus type (or PM domain) has a good reason to not return a positive number from ->prepare even though the driver thinks it would be OK to do that? The changes here would break that case I think, wouldn't they? I thought about adding a flag that would work if the ->prepare callback was not present. So device_prepare() would check that flag for NULL 'callback' only and then it would set 'ret' to 1 if the flag was set. Something like in the (untested) patch below. Wouldn't that be sufficient to cover the use cases you care about? > + spin_unlock_irq(&dev->power.lock); > + } > return 0; > } > > diff --git a/include/linux/pm.h b/include/linux/pm.h > index 2d29c64..2e41cfd 100644 > --- a/include/linux/pm.h > +++ b/include/linux/pm.h > @@ -553,6 +553,7 @@ struct dev_pm_info { > bool ignore_children:1; > bool early_init:1; /* Owned by the PM core */ > bool direct_complete:1; /* Owned by the PM core */ > + bool force_direct_complete:1; > spinlock_t lock; > #ifdef CONFIG_PM_SLEEP > struct list_head entry; > --- drivers/base/power/main.c | 2 ++ include/linux/pm.h | 1 + 2 files changed, 3 insertions(+) Index: linux-pm/drivers/base/power/main.c =================================================================== --- linux-pm.orig/drivers/base/power/main.c +++ linux-pm/drivers/base/power/main.c @@ -1589,6 +1589,8 @@ static int device_prepare(struct device trace_device_pm_callback_start(dev, info, state.event); ret = callback(dev); trace_device_pm_callback_end(dev, ret); + } else if (dev->power.direct_complete_default) { + ret = 1; } device_unlock(dev); Index: linux-pm/include/linux/pm.h =================================================================== --- linux-pm.orig/include/linux/pm.h +++ linux-pm/include/linux/pm.h @@ -553,6 +553,7 @@ struct dev_pm_info { bool ignore_children:1; bool early_init:1; /* Owned by the PM core */ bool direct_complete:1; /* Owned by the PM core */ + bool direct_complete_default:1; /* Ditto */ spinlock_t lock; #ifdef CONFIG_PM_SLEEP struct list_head entry; -- 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/