* Wu Zhangjin <wuzhangjin@xxxxxxxxx> wrote:
> +config HR_SCHED_CLOCK
> + bool "High Resolution sched_clock()"
> + depends on CSRC_R4K
> + default n
> + help
> + This option enables the MIPS c0 count based high resolution
> + sched_clock().
> +
> + If you need a ns precision timestamp, You are recommended to enable
> + this option. For example, If you are using the Ftrace subsystem to do
> + real time tracing, this option is needed.
s/You/you
> +
> + If unsure, disable it.
> +
> +config HR_SCHED_CLOCK_UPDATE
> + bool "Update sched_clock() automatically"
> + depends on HR_SCHED_CLOCK
> + default y
> + help
> + Because Some of the MIPS c0 count period is quite short and because
> + cnt32_to_63() needs to be called at least once per half period to
> + work properly, a kernel timer is needed to set up to ensure this
> + requirement is always met.
s/Some/some
Why is this a config option? I suspect that hardware that _needs_ this
keep-warm periodic tick we should enable it unconditionally and
automatically - otherwise the user can misconfigure the kernel with a
bad clock.
> +
> + If unusre, enable it.
s/unusre/unsure
> +
> +#
> # Timer Interrupt Frequency Configuration
> #
>
> diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
> index e95a3cd..4e52cca 100644
> --- a/arch/mips/kernel/csrc-r4k.c
> +++ b/arch/mips/kernel/csrc-r4k.c
> @@ -6,10 +6,64 @@
> * Copyright (C) 2007 by Ralf Baechle
> */
> #include <linux/clocksource.h>
> +#include <linux/cnt32_to_63.h>
> +#include <linux/timer.h>
> #include <linux/init.h>
>
> #include <asm/time.h>
>
> +/*
> + * MIPS' sched_clock implementation.
s/MIPS'/MIPS's
or
s/MIPS'/MIPS
> + *
> + * because cnt32_to_63() needs to be called at least once per half period to
> + * work properly, and some of the MIPS' frequency is very low, perhaps a kernel
> + * timer is needed to be set up to ensure this requirement is always met.
> + * please refer to arch/arm/plat-orion/time.c and include/linux/cnt32_to_63.h
s/please/Please
> + */
> +static unsigned long __maybe_unused tclk2ns_scale;
> +static unsigned long __maybe_unused tclk2ns_scale_factor;
__read_mostly?
> +
> +#ifdef CONFIG_HR_SCHED_CLOCK
> +unsigned long long notrace sched_clock(void)
> +{
> + unsigned long long v = cnt32_to_63(read_c0_count());
> + return (v * tclk2ns_scale) >> tclk2ns_scale_factor;
> +}
> +#endif
> +
> +static void __init __maybe_unused setup_sched_clock(struct clocksource *cs)
> +{
> + unsigned long long v;
> +
> + v = cs->mult;
> + /*
> + * We want an even value to automatically clear the top bit
> + * returned by cnt32_to_63() without an additional run time
> + * instruction. So if the LSB is 1 then round it up.
> + */
> + if (v & 1)
> + v++;
>
> + tclk2ns_scale = v;
> + tclk2ns_scale_factor = cs->shift;
> +}
> +
> +static struct timer_list __maybe_unused cnt32_to_63_keepwarm_timer;
> +
> +static void __maybe_unused cnt32_to_63_keepwarm(unsigned long data)
> +{
> + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data));
> + (void) sched_clock();
>
> +}
> +
> +static void __maybe_unused setup_sched_clock_update(unsigned long tclk)
> +{
> + unsigned long data;
> +
> + data = (0xffffffffUL / tclk / 2 - 2) * HZ;
> + setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, data);
> + mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data));
> +}
> +
> static cycle_t c0_hpt_read(struct clocksource *cs)
> {
> return read_c0_count();
> @@ -32,7 +86,13 @@ int __init init_r4k_clocksource(void)
>
> clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
>
> +#ifdef CONFIG_HR_SCHED_CLOCK
> + setup_sched_clock(&clocksource_mips);
> +#endif
> clocksource_register(&clocksource_mips);
>
> +#ifdef CONFIG_HR_SCHED_CLOCK_UPDATE
> + setup_sched_clock_update(mips_hpt_frequency);
> +#endif
> return 0;
You could make the functions inline and move the #ifdef into those
functions.
That wold also remove those __maybe_unused tags.
Thanks,
Ingo
