Messages in this thread Patch in this message | | | Date | Sun, 24 Apr 2022 12:47:26 +0100 (BST) | From | "Maciej W. Rozycki" <> | Subject | [PATCH 2/3] sched_clock: Use Hz as the unit for clock rate reporting below 4kHz |
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We have always used kHz as the unit for clock rates reported between 1MHz (inclusive) and 4MHz (exclusive), e.g.:
riscv_timer_init_dt: Registering clocksource cpuid [0] hartid [1] clocksource: riscv_clocksource: mask: 0xffffffffffffffff max_cycles: 0x1d854df40, max_idle_ns: 3526361616960 ns sched_clock: 64 bits at 1000kHz, resolution 1000ns, wraps every 2199023255500ns
This reduces the amount of data lost due to rounding, but hasn't been replicated for the kHz range when support was added for proper reporting of sub-kHz clock rates. Take the same approach then for rates between 1kHz (inclusive) and 4kHz (exclusive), also for consistency.
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk> Fixes: 2f0778afac79 ("ARM: 7205/2: sched_clock: allow sched_clock to be selected at runtime") --- Russell,
Please correct me if I am wrong with my guess for the origin of the 4MHz boundary as there's no mention of it with your commit 112f38a4a316 ("ARM: sched_clock: provide common infrastructure for sched_clock()"), which is where this code has come from.
Maciej --- kernel/time/sched_clock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
linux-sched-clock-rate-4khz.diff Index: linux-macro/kernel/time/sched_clock.c =================================================================== --- linux-macro.orig/kernel/time/sched_clock.c +++ linux-macro/kernel/time/sched_clock.c @@ -203,7 +203,7 @@ sched_clock_register(u64 (*read)(void), r = DIV_ROUND_CLOSEST(r, 1000000); r_unit = 'M'; } else { - if (r >= 1000) { + if (r >= 4000) { r = DIV_ROUND_CLOSEST(r, 1000); r_unit = 'k'; } else {
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