Commit ec05aa13 authored by Russell King's avatar Russell King
Browse files

ARM: nomadik: convert sched_clock() to use new infrastructure

Convert nomadik platforms to use the new sched_clock() infrastructure
for extending 32bit counters to full 64-bit nanoseconds.
Acked-by: default avatarLinus Walleij <>
Signed-off-by: default avatarRussell King <>
parent 08f26b1e
......@@ -14,6 +14,7 @@ if PLAT_NOMADIK
config HAS_MTU
Support for Multi Timer Unit. MTU provides access
to multiple interrupt generating programmable
......@@ -17,10 +17,9 @@
#include <linux/clk.h>
#include <linux/jiffies.h>
#include <linux/err.h>
#include <linux/cnt32_to_63.h>
#include <linux/timer.h>
#include <linux/sched.h>
#include <asm/mach/time.h>
#include <asm/sched_clock.h>
#include <plat/mtu.h>
......@@ -53,81 +52,24 @@ static struct clocksource nmdk_clksrc = {
* Override the global weak sched_clock symbol with this
* local implementation which uses the clocksource to get some
* better resolution when scheduling the kernel.
* Because the hardware timer period may be quite short
* (32.3 secs on the 133 MHz MTU timer selection on ux500)
* and because cnt32_to_63() needs to be called at least once per
* half period to work properly, a kernel keepwarm() timer is set up
* to ensure this requirement is always met.
* Also the sched_clock timer will wrap around at some point,
* here we set it to run continously for a year.
#define SCHED_CLOCK_MIN_WRAP 3600*24*365
static struct timer_list cnt32_to_63_keepwarm_timer;
static u32 sched_mult;
static u32 sched_shift;
unsigned long long notrace sched_clock(void)
u64 cycles;
u32 cyc;
if (unlikely(!mtu_base))
return 0;
cycles = cnt32_to_63(-readl(mtu_base + MTU_VAL(0)));
* sched_mult is guaranteed to be even so will
* shift out bit 63
return (cycles * sched_mult) >> sched_shift;
cyc = -readl(mtu_base + MTU_VAL(0));
return cyc_to_sched_clock(&cd, cyc, (u32)~0);
/* Just kick sched_clock every so often */
static void cnt32_to_63_keepwarm(unsigned long data)
static void notrace nomadik_update_sched_clock(void)
mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + data));
(void) sched_clock();
* Set up a timer to keep sched_clock():s 32_to_63 algorithm warm
* once in half a 32bit timer wrap interval.
static void __init nmdk_sched_clock_init(unsigned long rate)
u32 v;
unsigned long delta;
u64 days;
/* Find the apropriate mult and shift factors */
clocks_calc_mult_shift(&sched_mult, &sched_shift,
/* We need to multiply by an even number to get rid of bit 63 */
if (sched_mult & 1)
/* Let's see what we get, take max counter and scale it */
days = (0xFFFFFFFFFFFFFFFFLLU * sched_mult) >> sched_shift;
do_div(days, NSEC_PER_SEC);
do_div(days, (3600*24));
pr_info("sched_clock: using %d bits @ %lu Hz wrap in %lu days\n",
(64 - sched_shift), rate, (unsigned long) days);
* Program a timer to kick us at half 32bit wraparound
* Formula: seconds per wrap = (2^32) / f
v = 0xFFFFFFFFUL / rate;
/* We want half of the wrap time to keep cnt32_to_63 warm */
v /= 2;
pr_debug("sched_clock: prescaled timer rate: %lu Hz, "
"initialize keepwarm timer every %d seconds\n", rate, v);
/* Convert seconds to jiffies */
delta = msecs_to_jiffies(v*1000);
setup_timer(&cnt32_to_63_keepwarm_timer, cnt32_to_63_keepwarm, delta);
mod_timer(&cnt32_to_63_keepwarm_timer, round_jiffies(jiffies + delta));
u32 cyc = -readl(mtu_base + MTU_VAL(0));
update_sched_clock(&cd, cyc, (u32)~0);
/* Clockevent device: use one-shot mode */
......@@ -237,7 +179,7 @@ void __init nmdk_timer_init(void)
pr_err("timer: failed to initialize clock source %s\n",;
init_sched_clock(&cd, nomadik_update_sched_clock, 32, rate);
/* Timer 1 is used for events */
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment