lkml.org 
[lkml]   [2018]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] clocksource: riscv_timer: Provide sched_clock
From
On Mon, 03 Dec 2018 04:35:24 PST (-0800), anup@brainfault.org wrote:
> Currently, we don't have a sched_clock registered for RISC-V systems.
> This means Linux time keeping will use jiffies (running at HZ) as the
> default sched_clock.
>
> To avoid this, we explicity provide sched_clock using RISC-V rdtime
> instruction (similar to riscv_timer clocksource).
>
> Signed-off-by: Anup Patel <anup@brainfault.org>
> ---
> drivers/clocksource/riscv_timer.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
> index 084e97dc10ed..431892200a08 100644
> --- a/drivers/clocksource/riscv_timer.c
> +++ b/drivers/clocksource/riscv_timer.c
> @@ -8,6 +8,7 @@
> #include <linux/cpu.h>
> #include <linux/delay.h>
> #include <linux/irq.h>
> +#include <linux/sched_clock.h>
> #include <asm/smp.h>
> #include <asm/sbi.h>
>
> @@ -49,6 +50,11 @@ static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
> return get_cycles64();
> }
>
> +static u64 riscv_sched_clock(void)
> +{
> + return get_cycles64();
> +}
> +
> static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
> .name = "riscv_clocksource",
> .rating = 300,
> @@ -97,6 +103,9 @@ static int __init riscv_timer_init_dt(struct device_node *n)
> cs = per_cpu_ptr(&riscv_clocksource, cpuid);
> clocksource_register_hz(cs, riscv_timebase);
>
> + sched_clock_register(riscv_sched_clock,
> + BITS_PER_LONG, riscv_timebase);

Shouldn't this just be 64, not BITS_PER_LONG? We have 64-bit counters on
RV32I.

> +
> error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
> "clockevents/riscv/timer:starting",
> riscv_timer_starting_cpu, riscv_timer_dying_cpu);

\
 
 \ /
  Last update: 2018-12-06 21:33    [W:0.062 / U:2.876 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site