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-rw-r--r--arch/mips/kernel/time.c167
1 files changed, 167 insertions, 0 deletions
diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
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+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright 2001 MontaVista Software Inc.
+ * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
+ * Copyright (c) 2003, 2004 Maciej W. Rozycki
+ *
+ * Common time service routines for MIPS machines.
+ */
+#include <linux/bug.h>
+#include <linux/clockchips.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/param.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/export.h>
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+
+#include <asm/cpu-features.h>
+#include <asm/cpu-type.h>
+#include <asm/div64.h>
+#include <asm/time.h>
+
+#ifdef CONFIG_CPU_FREQ
+
+static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref);
+static DEFINE_PER_CPU(unsigned long, pcp_lpj_ref_freq);
+static unsigned long glb_lpj_ref;
+static unsigned long glb_lpj_ref_freq;
+
+static int cpufreq_callback(struct notifier_block *nb,
+ unsigned long val, void *data)
+{
+ struct cpufreq_freqs *freq = data;
+ struct cpumask *cpus = freq->policy->cpus;
+ unsigned long lpj;
+ int cpu;
+
+ /*
+ * Skip lpj numbers adjustment if the CPU-freq transition is safe for
+ * the loops delay. (Is this possible?)
+ */
+ if (freq->flags & CPUFREQ_CONST_LOOPS)
+ return NOTIFY_OK;
+
+ /* Save the initial values of the lpjes for future scaling. */
+ if (!glb_lpj_ref) {
+ glb_lpj_ref = boot_cpu_data.udelay_val;
+ glb_lpj_ref_freq = freq->old;
+
+ for_each_online_cpu(cpu) {
+ per_cpu(pcp_lpj_ref, cpu) =
+ cpu_data[cpu].udelay_val;
+ per_cpu(pcp_lpj_ref_freq, cpu) = freq->old;
+ }
+ }
+
+ /*
+ * Adjust global lpj variable and per-CPU udelay_val number in
+ * accordance with the new CPU frequency.
+ */
+ if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
+ (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
+ loops_per_jiffy = cpufreq_scale(glb_lpj_ref,
+ glb_lpj_ref_freq,
+ freq->new);
+
+ for_each_cpu(cpu, cpus) {
+ lpj = cpufreq_scale(per_cpu(pcp_lpj_ref, cpu),
+ per_cpu(pcp_lpj_ref_freq, cpu),
+ freq->new);
+ cpu_data[cpu].udelay_val = (unsigned int)lpj;
+ }
+ }
+
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpufreq_notifier = {
+ .notifier_call = cpufreq_callback,
+};
+
+static int __init register_cpufreq_notifier(void)
+{
+ return cpufreq_register_notifier(&cpufreq_notifier,
+ CPUFREQ_TRANSITION_NOTIFIER);
+}
+core_initcall(register_cpufreq_notifier);
+
+#endif /* CONFIG_CPU_FREQ */
+
+/*
+ * forward reference
+ */
+DEFINE_SPINLOCK(rtc_lock);
+EXPORT_SYMBOL(rtc_lock);
+
+static int null_perf_irq(void)
+{
+ return 0;
+}
+
+int (*perf_irq)(void) = null_perf_irq;
+
+EXPORT_SYMBOL(perf_irq);
+
+/*
+ * time_init() - it does the following things.
+ *
+ * 1) plat_time_init() -
+ * a) (optional) set up RTC routines,
+ * b) (optional) calibrate and set the mips_hpt_frequency
+ * (only needed if you intended to use cpu counter as timer interrupt
+ * source)
+ * 2) calculate a couple of cached variables for later usage
+ */
+
+unsigned int mips_hpt_frequency;
+EXPORT_SYMBOL_GPL(mips_hpt_frequency);
+
+static __init int cpu_has_mfc0_count_bug(void)
+{
+ switch (current_cpu_type()) {
+ case CPU_R4000PC:
+ case CPU_R4000SC:
+ case CPU_R4000MC:
+ /*
+ * V3.0 is documented as suffering from the mfc0 from count bug.
+ * Afaik this is the last version of the R4000. Later versions
+ * were marketed as R4400.
+ */
+ return 1;
+
+ case CPU_R4400PC:
+ case CPU_R4400SC:
+ case CPU_R4400MC:
+ /*
+ * The published errata for the R4400 up to 3.0 say the CPU
+ * has the mfc0 from count bug. This seems the last version
+ * produced.
+ */
+ return 1;
+ }
+
+ return 0;
+}
+
+void __init time_init(void)
+{
+ plat_time_init();
+
+ /*
+ * The use of the R4k timer as a clock event takes precedence;
+ * if reading the Count register might interfere with the timer
+ * interrupt, then we don't use the timer as a clock source.
+ * We may still use the timer as a clock source though if the
+ * timer interrupt isn't reliable; the interference doesn't
+ * matter then, because we don't use the interrupt.
+ */
+ if (mips_clockevent_init() != 0 || !cpu_has_mfc0_count_bug())
+ init_mips_clocksource();
+}