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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2007 by Ralf Baechle
*/
#include <linux/clocksource.h>
#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/sched_clock.h>
#include <asm/time.h>
static u64 c0_hpt_read(struct clocksource *cs)
{
return read_c0_count();
}
static struct clocksource clocksource_mips = {
.name = "MIPS",
.read = c0_hpt_read,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
static u64 __maybe_unused notrace r4k_read_sched_clock(void)
{
return read_c0_count();
}
static inline unsigned int rdhwr_count(void)
{
unsigned int count;
__asm__ __volatile__(
" .set push\n"
" .set mips32r2\n"
" rdhwr %0, $2\n"
" .set pop\n"
: "=r" (count));
return count;
}
static bool rdhwr_count_usable(void)
{
unsigned int prev, curr, i;
/*
* Older QEMUs have a broken implementation of RDHWR for the CP0 count
* which always returns a constant value. Try to identify this and don't
* use it in the VDSO if it is broken. This workaround can be removed
* once the fix has been in QEMU stable for a reasonable amount of time.
*/
for (i = 0, prev = rdhwr_count(); i < 100; i++) {
curr = rdhwr_count();
if (curr != prev)
return true;
prev = curr;
}
pr_warn("Not using R4K clocksource in VDSO due to broken RDHWR\n");
return false;
}
#ifdef CONFIG_CPU_FREQ
static bool __read_mostly r4k_clock_unstable;
static void r4k_clocksource_unstable(char *reason)
{
if (r4k_clock_unstable)
return;
r4k_clock_unstable = true;
pr_info("R4K timer is unstable due to %s\n", reason);
clocksource_mark_unstable(&clocksource_mips);
}
static int r4k_cpufreq_callback(struct notifier_block *nb,
unsigned long val, void *data)
{
if (val == CPUFREQ_POSTCHANGE)
r4k_clocksource_unstable("CPU frequency change");
return 0;
}
static struct notifier_block r4k_cpufreq_notifier = {
.notifier_call = r4k_cpufreq_callback,
};
static int __init r4k_register_cpufreq_notifier(void)
{
return cpufreq_register_notifier(&r4k_cpufreq_notifier,
CPUFREQ_TRANSITION_NOTIFIER);
}
core_initcall(r4k_register_cpufreq_notifier);
#endif /* !CONFIG_CPU_FREQ */
int __init init_r4k_clocksource(void)
{
if (!cpu_has_counter || !mips_hpt_frequency)
return -ENXIO;
/* Calculate a somewhat reasonable rating value */
clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
/*
* R2 onwards makes the count accessible to user mode so it can be used
* by the VDSO (HWREna is configured by configure_hwrena()).
*/
if (cpu_has_mips_r2_r6 && rdhwr_count_usable())
clocksource_mips.vdso_clock_mode = VDSO_CLOCKMODE_R4K;
clocksource_register_hz(&clocksource_mips, mips_hpt_frequency);
#ifndef CONFIG_CPU_FREQ
sched_clock_register(r4k_read_sched_clock, 32, mips_hpt_frequency);
#endif
return 0;
}
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