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| author |   Rob Herring <rob.herring@calxeda.com> | 2013-03-11 16:23:46 -0500 |
|---|---|---|
| committer | Rob Herring <rob.herring@calxeda.com> | 2013-04-11 15:11:14 -0500 |
| commit | 023796b9be3a77481cd5ee0b64a13a55bb0d5df4 (patch) | |
| tree | ecf5a33e6deb251eee4cb61a12b5f60273c72bf2 | |
| parent | ARM: make sched_clock just call a function pointer (diff) | |
| download | linux-dev-023796b9be3a77481cd5ee0b64a13a55bb0d5df4.tar.xz linux-dev-023796b9be3a77481cd5ee0b64a13a55bb0d5df4.zip | |
ARM: arch_timer: use full 64-bit counter for sched_clock
Only 32-bits of the arch timer were being used and wrapping was needlessly
being done in s/w. By using the full counter (56-64 bits), we don't need
to deal with wrapping and can simplify the implementation when using
arch timer.
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
| -rw-r--r-- | arch/arm/kernel/arch_timer.c | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c index d957a51435d8..80c458fc4a30 100644 --- a/arch/arm/kernel/arch_timer.c +++ b/arch/arm/kernel/arch_timer.c @@ -22,9 +22,11 @@ static unsigned long arch_timer_read_counter_long(void) return arch_timer_read_counter(); } -static u32 arch_timer_read_counter_u32(void) +static u32 sched_clock_mult __read_mostly; + +static unsigned long long notrace arch_timer_sched_clock(void) { - return arch_timer_read_counter(); + return arch_timer_read_counter() * sched_clock_mult; } static struct delay_timer arch_delay_timer; @@ -52,10 +54,16 @@ int __init arch_timer_of_register(void) int __init arch_timer_sched_clock_init(void) { - if (arch_timer_get_rate() == 0) + u32 arch_timer_rate = arch_timer_get_rate(); + + if (arch_timer_rate == 0) return -ENXIO; - setup_sched_clock(arch_timer_read_counter_u32, - 32, arch_timer_get_rate()); + /* Cache the sched_clock multiplier to save a divide in the hot path. */ + sched_clock_mult = NSEC_PER_SEC / arch_timer_rate; + sched_clock_func = arch_timer_sched_clock; + pr_info("sched_clock: ARM arch timer >56 bits at %ukHz, resolution %uns\n", + arch_timer_rate / 1000, sched_clock_mult); + return 0; } |