[PATCH] AVR32: Switch to generic timekeeping framework
From: Haavard Skinnemoen
Date: Tue Aug 08 2006 - 09:47:06 EST
Define CONFIG_GENERIC_TIME and remove arch-specific versions of
do_{get,set}timeofday(). Define and use a clocksource based on the
AVR32 cycle counter.
Also clean up asm/timex.h a bit, including defining CLOCK_TICK_RATE
to a "good cheat value" borrowed from MIPS instead of the i8254 value
used by "everyone" else, which is really quite pointless on AVR32.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@xxxxxxxxx>
---
arch/avr32/Kconfig | 4 +
arch/avr32/kernel/time.c | 172 +++++++++-------------------------------------
include/asm-avr32/timex.h | 26 ++++--
3 files changed, 59 insertions(+), 143 deletions(-)
Index: linux-2.6.18-rc3-mm2/arch/avr32/Kconfig
===================================================================
--- linux-2.6.18-rc3-mm2.orig/arch/avr32/Kconfig 2006-08-07 13:50:36.000000000 +0200
+++ linux-2.6.18-rc3-mm2/arch/avr32/Kconfig 2006-08-08 15:28:05.000000000 +0200
@@ -38,6 +38,10 @@ config RWSEM_GENERIC_SPINLOCK
bool
default y
+config GENERIC_TIME
+ bool
+ default y
+
config RWSEM_XCHGADD_ALGORITHM
bool
Index: linux-2.6.18-rc3-mm2/arch/avr32/kernel/time.c
===================================================================
--- linux-2.6.18-rc3-mm2.orig/arch/avr32/kernel/time.c 2006-08-07 13:50:36.000000000 +0200
+++ linux-2.6.18-rc3-mm2/arch/avr32/kernel/time.c 2006-08-08 15:36:48.000000000 +0200
@@ -10,6 +10,7 @@
*/
#include <linux/clk.h>
+#include <linux/clocksource.h>
#include <linux/time.h>
#include <linux/module.h>
#include <linux/interrupt.h>
@@ -25,9 +26,19 @@
#include <asm/io.h>
#include <asm/sections.h>
-extern unsigned long wall_jiffies;
+static cycle_t read_cycle_count(void)
+{
+ return (cycle_t)sysreg_read(COUNT);
+}
-#define USECS_PER_JIFFY (1000000 / HZ)
+static struct clocksource clocksource_avr32 = {
+ .name = "avr32",
+ .rating = 350,
+ .read = read_cycle_count,
+ .mask = CLOCKSOURCE_MASK(32),
+ .shift = 16,
+ .is_continuous = 1,
+};
/*
* By default we provide the null RTC ops
@@ -45,9 +56,6 @@ static int null_rtc_set_time(unsigned lo
static unsigned long (*rtc_get_time)(void) = null_rtc_get_time;
static int (*rtc_set_time)(unsigned long) = null_rtc_set_time;
-/* usecs per counter cycle, shifted left by 32 bits */
-static unsigned int sll32_usecs_per_cycle;
-
/* how many counter cycles in a jiffy? */
static unsigned long cycles_per_jiffy;
@@ -57,7 +65,7 @@ static unsigned int timerhi, timerlo;
/* the count value for the next timer interrupt */
static unsigned int expirelo;
-static inline void avr32_timer_ack(void)
+static void avr32_timer_ack(void)
{
unsigned int count;
@@ -78,7 +86,7 @@ static inline void avr32_timer_ack(void)
}
}
-static inline unsigned int avr32_hpt_read(void)
+static unsigned int avr32_hpt_read(void)
{
return sysreg_read(COUNT);
}
@@ -92,7 +100,7 @@ static inline unsigned int avr32_hpt_rea
* probably to make sure we don't get any timer interrupts while we
* are messing with the counter.
*/
-static inline void avr32_hpt_init(unsigned int count)
+static void avr32_hpt_init(unsigned int count)
{
count = sysreg_read(COUNT) - count;
expirelo = (count / cycles_per_jiffy + 1) * cycles_per_jiffy;
@@ -110,116 +118,6 @@ unsigned long long sched_clock(void)
return (unsigned long long)jiffies * (1000000000 / HZ);
}
-/* Taken from MIPS fixed_rate_gettimeoffset */
-static unsigned long do_gettimeoffset(void)
-{
- unsigned long long tmp;
- unsigned long res;
- u32 count;
-
- /* Get latest timer tick in absolute kernel time */
- count = avr32_hpt_read();
-
- /* ... relative to previous jiffy (32 bits is enough) */
- count -= timerlo;
-
- /* Divide by cycles_per_usec */
- asm("mulu.d %0, %1, %2"
- : "=r"(tmp)
- : "r"(count), "r"(sll32_usecs_per_cycle));
- res = tmp >> 32;
-
- /*
- * Due to possible jiffies inconsistencies, we need to check
- * the result so that we'll get a timer that is monotonic.
- */
- if (res >= USECS_PER_JIFFY)
- res = USECS_PER_JIFFY - 1;
-
- return res;
-}
-
-/* This one is taken from MIPS */
-void do_gettimeofday(struct timeval *tv)
-{
- unsigned long seq;
- unsigned long lost;
- unsigned long usec, sec;
- unsigned long max_ntp_tick = tick_usec - tickadj;
-
- do {
- seq = read_seqbegin(&xtime_lock);
- usec = do_gettimeoffset();
- lost = jiffies - wall_jiffies;
-
- /*
- * If time_adjust is negative then NTP is slowing the
- * clock, so make sure not to go into next possible
- * interval. Better to lose some accuracy than have
- * time go backwards..
- */
- if (unlikely(time_adjust < 0)) {
- usec = min(usec, max_ntp_tick);
-
- if (lost)
- usec += lost * max_ntp_tick;
- } else if (unlikely(lost)) {
- usec += lost * tick_usec;
- }
-
- sec = xtime.tv_sec;
- usec += xtime.tv_nsec / 1000;
- } while (read_seqretry(&xtime_lock, seq));
-
- while (usec >= 1000000) {
- usec -= 1000000;
- sec++;
- }
-
- tv->tv_sec = sec;
- tv->tv_usec = usec;
-}
-
-EXPORT_SYMBOL(do_gettimeofday);
-
-int do_settimeofday(struct timespec *tv)
-{
- time_t wtm_sec, sec = tv->tv_sec;
- long wtm_nsec, nsec = tv->tv_nsec;
-
- if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
- return -EINVAL;
-
- write_seqlock_irq(&xtime_lock);
-
- /*
- * This is revolting. We need to set "xtime" correctly.
- * However, the value in this location is the value at the
- * most recent update of wall time. Discover what correction
- * gettimeofday() would have made, and undo it!
- */
- nsec -= do_gettimeoffset() * NSEC_PER_USEC;
- nsec -= (jiffies - wall_jiffies) * tick_nsec;
-
- wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
- wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
-
- set_normalized_timespec(&xtime, sec, nsec);
- set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
-
- time_adjust = 0;
- time_status |= STA_UNSYNC;
- time_maxerror = NTP_PHASE_LIMIT;
- time_esterror = NTP_PHASE_LIMIT;
-
- write_sequnlock_irq(&xtime_lock);
- clock_was_set();
-
- return 0;
-}
-
-EXPORT_SYMBOL(do_settimeofday);
-
/*
* local_timer_interrupt() does profiling and process accounting on a
* per-CPU basis.
@@ -264,8 +162,6 @@ timer_interrupt(int irq, void *dev_id, s
return IRQ_HANDLED;
}
-static unsigned int avr32_hpt_frequency;
-
static struct irqaction timer_irqaction = {
.handler = timer_interrupt,
.flags = IRQF_DISABLED,
@@ -274,6 +170,7 @@ static struct irqaction timer_irqaction
void __init time_init(void)
{
+ unsigned long mult, shift, count_hz;
int ret;
xtime.tv_sec = rtc_get_time();
@@ -286,22 +183,22 @@ void __init time_init(void)
(unsigned long)sysreg_read(COUNT),
(unsigned long)sysreg_read(COMPARE));
- if (!avr32_hpt_frequency && boot_cpu_data.clk)
- avr32_hpt_frequency = clk_get_rate(boot_cpu_data.clk);
-
- if (avr32_hpt_frequency) {
- cycles_per_jiffy = (avr32_hpt_frequency + HZ / 2) / HZ;
+ count_hz = clk_get_rate(boot_cpu_data.clk);
+ shift = clocksource_avr32.shift;
+ mult = clocksource_hz2mult(count_hz, shift);
+ clocksource_avr32.mult = mult;
+
+ printk("Cycle counter: mult=%lu, shift=%lu\n", mult, shift);
+
+ {
+ u64 tmp;
+
+ tmp = TICK_NSEC;
+ tmp <<= shift;
+ tmp += mult / 2;
+ do_div(tmp, mult);
- /* 10^6 * 2^32 / avr32_hpt_frequency */
- {
- u64 tmp = 1000000ULL << 32;
- do_div(tmp, avr32_hpt_frequency);
- sll32_usecs_per_cycle = tmp;
- }
-
- printk("Using %u.%03u MHz high precision timer.\n",
- ((avr32_hpt_frequency + 500) / 1000) / 1000,
- ((avr32_hpt_frequency + 500) / 1000) % 1000);
+ cycles_per_jiffy = tmp;
}
/* This sets up the high precision timer for the first interrupt. */
@@ -311,6 +208,11 @@ void __init time_init(void)
(unsigned long)sysreg_read(COUNT),
(unsigned long)sysreg_read(COMPARE));
+ ret = clocksource_register(&clocksource_avr32);
+ if (ret)
+ printk(KERN_ERR
+ "timer: could not register clocksource: %d\n", ret);
+
ret = setup_irq(0, &timer_irqaction);
if (ret)
printk("timer: could not request IRQ 0: %d\n", ret);
Index: linux-2.6.18-rc3-mm2/include/asm-avr32/timex.h
===================================================================
--- linux-2.6.18-rc3-mm2.orig/include/asm-avr32/timex.h 2006-08-07 13:50:36.000000000 +0200
+++ linux-2.6.18-rc3-mm2/include/asm-avr32/timex.h 2006-08-08 15:36:48.000000000 +0200
@@ -8,17 +8,27 @@
#ifndef __ASM_AVR32_TIMEX_H
#define __ASM_AVR32_TIMEX_H
-/* FIXME: I really have no idea... */
-#define CLOCK_TICK_RATE 1193180 /* Underlying HZ */
-#define CLOCK_TICK_FACTOR 20 /* Factor of both 1000000 and CLOCK_TICK_RATE */
-#define FINETUNE ((((((long)LATCH * HZ - CLOCK_TICK_RATE) << SHIFT_HZ) * \
- (1000000/CLOCK_TICK_FACTOR) / (CLOCK_TICK_RATE/CLOCK_TICK_FACTOR)) \
- << (SHIFT_SCALE-SHIFT_HZ)) / HZ)
+/*
+ * This is the frequency of the timer used for Linux's timer interrupt.
+ * The value should be defined as accurate as possible or under certain
+ * circumstances Linux timekeeping might become inaccurate or fail.
+ *
+ * For many system the exact clockrate of the timer isn't known but due to
+ * the way this value is used we can get away with a wrong value as long
+ * as this value is:
+ *
+ * - a multiple of HZ
+ * - a divisor of the actual rate
+ *
+ * 500000 is a good such cheat value.
+ *
+ * The obscure number 1193182 is the same as used by the original i8254
+ * time in legacy PC hardware; the chip is never found in AVR32 systems.
+ */
+#define CLOCK_TICK_RATE 500000 /* Underlying HZ */
typedef unsigned long cycles_t;
-extern cycles_t cacheflush_time;
-
static inline cycles_t get_cycles (void)
{
return 0;
-
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