Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758342Ab1COVnQ (ORCPT ); Tue, 15 Mar 2011 17:43:16 -0400 Received: from ogre.sisk.pl ([217.79.144.158]:36101 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752230Ab1COVnO (ORCPT ); Tue, 15 Mar 2011 17:43:14 -0400 From: "Rafael J. Wysocki" To: LKML Subject: [Update, v2] Re: [PATCH 7/8] cpufreq: Use syscore_ops for boot CPU suspend/resume Date: Tue, 15 Mar 2011 22:43:02 +0100 User-Agent: KMail/1.13.6 (Linux/2.6.38+; KDE/4.6.0; x86_64; ; ) Cc: Len Brown , Greg KH , Kay Sievers , Jesse Barnes , Linux PM mailing list , "H. Peter Anvin" , mingo@redhat.com, tglx@linutronix.de, Dave Jones , Alan Stern , Avi Kivity References: <201103100131.58206.rjw@sisk.pl> <201103122212.40828.rjw@sisk.pl> <201103122220.30173.rjw@sisk.pl> In-Reply-To: <201103122220.30173.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201103152243.02809.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6782 Lines: 201 On Saturday, March 12, 2011, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > The cpufreq subsystem uses sysdev suspend and resume for > executing cpufreq_suspend() and cpufreq_resume(), respectively, > during system suspend, after interrupts have been switched off on the > boot CPU, and during system resume, while interrupts are still off on > the boot CPU. In both cases the other CPUs are off-line at the > relevant point (either they have been switched off via CPU hotplug > during suspend, or they haven't been switched on yet during resume). > For this reason, although it may seem that cpufreq_suspend() and > cpufreq_resume() are executed for all CPUs in the system, they are > only called for the boot CPU in fact, which is quite confusing. > > To remove the confusion and to prepare for elimiating sysdev > suspend and resume operations from the kernel enirely, convernt > cpufreq to using a struct syscore_ops object for the boot CPU > suspend and resume and rename the callbacks so that their names > reflect their purpose. In addition, put some explanatory remarks > into their kerneldoc comments. I had to modify this patch, because the previous version had problems with systems that don't support cpufreq. The updated patch (which is appended) also simplifies the code even further. Thanks, Rafael --- From: Rafael J. Wysocki Subject: cpufreq: Use syscore_ops for boot CPU suspend/resume (v2) The cpufreq subsystem uses sysdev suspend and resume for executing cpufreq_suspend() and cpufreq_resume(), respectively, during system suspend, after interrupts have been switched off on the boot CPU, and during system resume, while interrupts are still off on the boot CPU. In both cases the other CPUs are off-line at the relevant point (either they have been switched off via CPU hotplug during suspend, or they haven't been switched on yet during resume). For this reason, although it may seem that cpufreq_suspend() and cpufreq_resume() are executed for all CPUs in the system, they are only called for the boot CPU in fact, which is quite confusing. To remove the confusion and to prepare for elimiating sysdev suspend and resume operations from the kernel enirely, convernt cpufreq to using a struct syscore_ops object for the boot CPU suspend and resume and rename the callbacks so that their names reflect their purpose. In addition, put some explanatory remarks into their kerneldoc comments. Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cpufreq.c | 66 ++++++++++++++++++---------------------------- 1 file changed, 26 insertions(+), 40 deletions(-) Index: linux-2.6/drivers/cpufreq/cpufreq.c =================================================================== --- linux-2.6.orig/drivers/cpufreq/cpufreq.c +++ linux-2.6/drivers/cpufreq/cpufreq.c @@ -28,6 +28,7 @@ #include #include #include +#include #include @@ -1340,35 +1341,31 @@ out: } EXPORT_SYMBOL(cpufreq_get); +static struct sysdev_driver cpufreq_sysdev_driver = { + .add = cpufreq_add_dev, + .remove = cpufreq_remove_dev, +}; + /** - * cpufreq_suspend - let the low level driver prepare for suspend + * cpufreq_bp_suspend - Prepare the boot CPU for system suspend. + * + * This function is only executed for the boot processor. The other CPUs + * have been put offline by means of CPU hotplug. */ - -static int cpufreq_suspend(struct sys_device *sysdev, pm_message_t pmsg) +static int cpufreq_bp_suspend(void) { int ret = 0; - int cpu = sysdev->id; + int cpu = smp_processor_id(); struct cpufreq_policy *cpu_policy; dprintk("suspending cpu %u\n", cpu); - if (!cpu_online(cpu)) - return 0; - - /* we may be lax here as interrupts are off. Nonetheless - * we need to grab the correct cpu policy, as to check - * whether we really run on this CPU. - */ - + /* If there's no policy for the boot CPU, we have nothing to do. */ cpu_policy = cpufreq_cpu_get(cpu); if (!cpu_policy) - return -EINVAL; - - /* only handle each CPU group once */ - if (unlikely(cpu_policy->cpu != cpu)) - goto out; + return 0; if (cpufreq_driver->suspend) { ret = cpufreq_driver->suspend(cpu_policy); @@ -1377,13 +1374,12 @@ static int cpufreq_suspend(struct sys_de "step on CPU %u\n", cpu_policy->cpu); } -out: cpufreq_cpu_put(cpu_policy); return ret; } /** - * cpufreq_resume - restore proper CPU frequency handling after resume + * cpufreq_bp_resume - Restore proper frequency handling of the boot CPU. * * 1.) resume CPUfreq hardware support (cpufreq_driver->resume()) * 2.) schedule call cpufreq_update_policy() ASAP as interrupts are @@ -1391,31 +1387,23 @@ out: * what we believe it to be. This is a bit later than when it * should be, but nonethteless it's better than calling * cpufreq_driver->get() here which might re-enable interrupts... + * + * This function is only executed for the boot CPU. The other CPUs have not + * been turned on yet. */ -static int cpufreq_resume(struct sys_device *sysdev) +static void cpufreq_bp_resume(void) { int ret = 0; - int cpu = sysdev->id; + int cpu = smp_processor_id(); struct cpufreq_policy *cpu_policy; dprintk("resuming cpu %u\n", cpu); - if (!cpu_online(cpu)) - return 0; - - /* we may be lax here as interrupts are off. Nonetheless - * we need to grab the correct cpu policy, as to check - * whether we really run on this CPU. - */ - + /* If there's no policy for the boot CPU, we have nothing to do. */ cpu_policy = cpufreq_cpu_get(cpu); if (!cpu_policy) - return -EINVAL; - - /* only handle each CPU group once */ - if (unlikely(cpu_policy->cpu != cpu)) - goto fail; + return; if (cpufreq_driver->resume) { ret = cpufreq_driver->resume(cpu_policy); @@ -1430,14 +1418,11 @@ static int cpufreq_resume(struct sys_dev fail: cpufreq_cpu_put(cpu_policy); - return ret; } -static struct sysdev_driver cpufreq_sysdev_driver = { - .add = cpufreq_add_dev, - .remove = cpufreq_remove_dev, - .suspend = cpufreq_suspend, - .resume = cpufreq_resume, +static struct syscore_ops cpufreq_syscore_ops = { + .suspend = cpufreq_bp_suspend, + .resume = cpufreq_bp_resume, }; @@ -2002,6 +1987,7 @@ static int __init cpufreq_core_init(void cpufreq_global_kobject = kobject_create_and_add("cpufreq", &cpu_sysdev_class.kset.kobj); BUG_ON(!cpufreq_global_kobject); + register_syscore_ops(&cpufreq_syscore_ops); return 0; } -- 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/