diff options
| author | Stefan Agner <stefan@agner.ch> | 2009-05-12 10:30:41 -0700 |
|---|---|---|
| committer | Nicolas Pitre <nico@cam.org> | 2009-06-08 13:04:54 -0400 |
| commit | 8a3269fc21cc4405d80b362139c078cf655a505a (patch) | |
| tree | 5b8167964d803515471e1a7450eb1f4fd74655c9 /arch/arm | |
| parent | e50b6befae9ea91c2d190fb78ff1e06a0b950add (diff) | |
[ARM] orion: sched_clock implementation for orion platforms
sched_clock implementation for orion platform. Its realized using
free-running clocksource timer, which provides a resolution of 7.5ns
(depending on tclk). It's derived from PXA's sched_clock implementation.
[ nico: renamed orion2ns to tclk2ns, fixed max value in the comment ]
Signed-off-by: Stefan Agner <stefan.agner@yahoo.com>
Signed-off-by: Nicolas Pitre <nico@marvell.com>
Diffstat (limited to 'arch/arm')
| -rw-r--r-- | arch/arm/plat-orion/time.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/arch/arm/plat-orion/time.c b/arch/arm/plat-orion/time.c index de8a001fc3a..b856cec8170 100644 --- a/arch/arm/plat-orion/time.c +++ b/arch/arm/plat-orion/time.c @@ -17,6 +17,9 @@ #include <linux/irq.h> #include <asm/mach/time.h> #include <mach/bridge-regs.h> +#include <mach/hardware.h> +#include <linux/sched.h> +#include <linux/cnt32_to_63.h> /* * Number of timer ticks per jiffy. @@ -39,6 +42,36 @@ static u32 ticks_per_jiffy; /* + * Orion's sched_clock implementation. It has a resolution of + * at least 7.5ns (133MHz TCLK) and a maximum value of 834 days. + */ +#define TCLK2NS_SCALE_FACTOR 8 + +static unsigned long tclk2ns_scale; + +static void __init set_tclk2ns_scale(unsigned long tclk) +{ + unsigned long long v = NSEC_PER_SEC; + v <<= TCLK2NS_SCALE_FACTOR; + v += tclk/2; + do_div(v, tclk); + /* + * 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; +} + +unsigned long long sched_clock(void) +{ + unsigned long long v = cnt32_to_63(0xffffffff - readl(TIMER0_VAL)); + return (v * tclk2ns_scale) >> TCLK2NS_SCALE_FACTOR; +} + +/* * Clocksource handling. */ static cycle_t orion_clksrc_read(struct clocksource *cs) @@ -176,6 +209,10 @@ void __init orion_time_init(unsigned int irq, unsigned int tclk) ticks_per_jiffy = (tclk + HZ/2) / HZ; + /* + * Set scale for sched_clock + */ + set_tclk2ns_scale(tclk); /* * Setup free-running clocksource timer (interrupts |