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mips: csrc-r4k: Mark R4K timer as unstable if CPU freq changes

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Commit 07d69579e7 ("MIPS: Don't register r4k sched clock when CPUFREQ
enabled") disabled the r4k-clock usage for scheduler ticks counting due
to the scheduler being non-tolerant for unstable clocks sources. For the
same reason the clock should be used in the system clocksource framework
with care. As soon as CPU frequency changes the clocksource framework
should be notified about this by marking the R4K timer being unstable
(which it really is, since the ticks rate has been changed synchronously
with the CPU frequency).

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
This commit is contained in:
Serge Semin 2020-05-21 17:07:23 +03:00 committed by Thomas Bogendoerfer
parent ed26aacfb5
commit 3858642805
2 changed files with 41 additions and 0 deletions
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1
arch/mips/Kconfig
View File

@ -1108,6 +1108,7 @@ config CSRC_IOASIC
bool
config CSRC_R4K
select CLOCKSOURCE_WATCHDOG if CPU_FREQ
bool
config CSRC_SB1250

40
arch/mips/kernel/csrc-r4k.c
View File

@ -6,6 +6,7 @@
* Copyright (C) 2007 by Ralf Baechle
*/
#include <linux/clocksource.h>
#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/sched_clock.h>
@ -65,6 +66,45 @@ static bool rdhwr_count_usable(void)
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)