Commit 07d69579e7fe ("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 <[email protected]> Cc: Alexey Malahov <[email protected]> Cc: Thomas Bogendoerfer <[email protected]> Cc: Paul Burton <[email protected]> Cc: Ralf Baechle <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Rob Herring <[email protected]> Cc: [email protected] --- arch/mips/Kconfig | 1 + arch/mips/kernel/csrc-r4k.c | 40 +++++++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig index 2747b1b2d435..f347312ecd74 100644 --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -1108,6 +1108,7 @@ config CSRC_IOASIC bool config CSRC_R4K + select CLOCKSOURCE_WATCHDOG if CPU_FREQ bool config CSRC_SB1250 diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c index 437dda64fd7a..edc4afc080fa 100644 --- a/arch/mips/kernel/csrc-r4k.c +++ b/arch/mips/kernel/csrc-r4k.c @@ -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) -- 2.25.1
