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linux/drivers/clocksource/dummy_timer.c

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clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
/*
* linux/drivers/clocksource/dummy_timer.c
*
* Copyright (C) 2013 ARM Ltd.
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/clockchips.h>
#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/percpu.h>
#include <linux/cpumask.h>
static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);
clocksource+irqchip: delete __cpuinit usage from all related files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. This removes all the drivers/clocksource and drivers/irqchip uses of the __cpuinit macros from all C files. [1] https://lkml.org/lkml/2013/5/20/589 Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 23:32:08 +08:00
static void dummy_timer_setup(void)
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
{
int cpu = smp_processor_id();
time: Replace __get_cpu_var uses Convert uses of __get_cpu_var for creating a address from a percpu offset to this_cpu_ptr. The two cases where get_cpu_var is used to actually access a percpu variable are changed to use this_cpu_read/raw_cpu_read. Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2014-08-18 01:30:25 +08:00
struct clock_event_device *evt = raw_cpu_ptr(&dummy_timer_evt);
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
evt->name = "dummy_timer";
evt->features = CLOCK_EVT_FEAT_PERIODIC |
CLOCK_EVT_FEAT_ONESHOT |
CLOCK_EVT_FEAT_DUMMY;
evt->rating = 100;
evt->cpumask = cpumask_of(cpu);
clockevents_register_device(evt);
}
clocksource+irqchip: delete __cpuinit usage from all related files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. This removes all the drivers/clocksource and drivers/irqchip uses of the __cpuinit macros from all C files. [1] https://lkml.org/lkml/2013/5/20/589 Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 23:32:08 +08:00
static int dummy_timer_cpu_notify(struct notifier_block *self,
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
unsigned long action, void *hcpu)
{
if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
dummy_timer_setup();
return NOTIFY_OK;
}
clocksource+irqchip: delete __cpuinit usage from all related files The __cpuinit type of throwaway sections might have made sense some time ago when RAM was more constrained, but now the savings do not offset the cost and complications. For example, the fix in commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time") is a good example of the nasty type of bugs that can be created with improper use of the various __init prefixes. After a discussion on LKML[1] it was decided that cpuinit should go the way of devinit and be phased out. Once all the users are gone, we can then finally remove the macros themselves from linux/init.h. This removes all the drivers/clocksource and drivers/irqchip uses of the __cpuinit macros from all C files. [1] https://lkml.org/lkml/2013/5/20/589 Cc: John Stultz <john.stultz@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2013-06-19 23:32:08 +08:00
static struct notifier_block dummy_timer_cpu_nb = {
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
.notifier_call = dummy_timer_cpu_notify,
};
static int __init dummy_timer_register(void)
{
clocksource, dummy-timer: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the clocksource dummy-timer code by using this latter form of callback registration. Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 04:40:23 +08:00
int err = 0;
cpu_notifier_register_begin();
err = __register_cpu_notifier(&dummy_timer_cpu_nb);
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
if (err)
clocksource, dummy-timer: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the clocksource dummy-timer code by using this latter form of callback registration. Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 04:40:23 +08:00
goto out;
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
/* We won't get a call on the boot CPU, so register immediately */
if (num_possible_cpus() > 1)
dummy_timer_setup();
clocksource, dummy-timer: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the clocksource dummy-timer code by using this latter form of callback registration. Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2014-03-11 04:40:23 +08:00
out:
cpu_notifier_register_done();
return err;
clocksource: Add generic dummy timer driver Several architectures have a dummy timer driver tightly coupled with their broadcast code to support machines without cpu-local timers (or where there is a lack of driver support). Since 12ad100046: "clockevents: Add generic timer broadcast function" it's been possible to write broadcast-capable timer drivers decoupled from the broadcast mechanism. We can use this functionality to implement a generic dummy timer driver that can be shared by all architectures with generic tick broadcast (ARCH_HAS_TICK_BROADCAST). This patch implements a generic dummy timer using this facility. [sboyd: Make percpu data static, use __this_cpu_ptr(), move to early_initcall to properly register on each CPU, only register if more than one CPU possible] Signed-off-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Acked-by: Marc Zyngier <marc.zyngier@arm.com>, Cc: John Stultz <john.stultz@linaro.org> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1370291642-13259-3-git-send-email-sboyd@codeaurora.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-06-04 04:33:53 +08:00
}
early_initcall(dummy_timer_register);
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