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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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064706514e
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>
70 lines
1.7 KiB
C
70 lines
1.7 KiB
C
/*
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* linux/drivers/clocksource/dummy_timer.c
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*
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* Copyright (C) 2013 ARM Ltd.
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/clockchips.h>
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#include <linux/cpu.h>
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#include <linux/init.h>
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#include <linux/percpu.h>
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#include <linux/cpumask.h>
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static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);
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static void dummy_timer_set_mode(enum clock_event_mode mode,
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struct clock_event_device *evt)
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{
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/*
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* Core clockevents code will call this when exchanging timer devices.
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* We don't need to do anything here.
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*/
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}
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static void __cpuinit dummy_timer_setup(void)
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{
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int cpu = smp_processor_id();
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struct clock_event_device *evt = __this_cpu_ptr(&dummy_timer_evt);
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evt->name = "dummy_timer";
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evt->features = CLOCK_EVT_FEAT_PERIODIC |
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CLOCK_EVT_FEAT_ONESHOT |
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CLOCK_EVT_FEAT_DUMMY;
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evt->rating = 100;
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evt->set_mode = dummy_timer_set_mode;
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evt->cpumask = cpumask_of(cpu);
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clockevents_register_device(evt);
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}
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static int __cpuinit dummy_timer_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
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dummy_timer_setup();
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return NOTIFY_OK;
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}
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static struct notifier_block dummy_timer_cpu_nb __cpuinitdata = {
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.notifier_call = dummy_timer_cpu_notify,
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};
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static int __init dummy_timer_register(void)
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{
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int err = register_cpu_notifier(&dummy_timer_cpu_nb);
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if (err)
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return err;
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/* We won't get a call on the boot CPU, so register immediately */
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if (num_possible_cpus() > 1)
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dummy_timer_setup();
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return 0;
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}
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early_initcall(dummy_timer_register);
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