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Subject[patch 3/3] xtensa: ccount clocksource
From: Johannes Weiner <hannes@cmpxchg.org>

Switch to GENERIC_TIME by using the ccount register as a clock source.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
arch/xtensa/Kconfig | 3 +
arch/xtensa/kernel/time.c | 92 ++++++++++------------------------------------
2 files changed, 23 insertions(+), 72 deletions(-)
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -45,6 +45,9 @@ config HZ
int
default 100

+config GENERIC_TIME
+ def_bool y
+
source "init/Kconfig"
source "kernel/Kconfig.freezer"

--- a/arch/xtensa/kernel/time.c
+++ b/arch/xtensa/kernel/time.c
@@ -14,6 +14,7 @@

#include <linux/errno.h>
#include <linux/time.h>
+#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/init.h>
@@ -29,6 +30,19 @@ unsigned long ccount_per_jiffy; /* per
unsigned long nsec_per_ccount; /* nsec per ccount increment */
#endif

+static cycle_t ccount_read(void)
+{
+ return (cycle_t)get_ccount();
+}
+
+static struct clocksource ccount_clocksource = {
+ .name = "ccount",
+ .rating = 200,
+ .read = ccount_read,
+ .mask = CLOCKSOURCE_MASK(32),
+ .mult = NSEC_PER_CCOUNT,
+};
+
static irqreturn_t timer_interrupt(int irq, void *dev_id);
static struct irqaction timer_irqaction = {
.handler = timer_interrupt,
@@ -38,9 +52,11 @@ static struct irqaction timer_irqaction

void __init time_init(void)
{
- /* The platform must provide a function to calibrate the processor
- * speed for the CALIBRATE.
- */
+ xtime.tv_nsec = 0;
+ xtime.tv_sec = read_persistent_clock();
+
+ set_normalized_timespec(&wall_to_monotonic,
+ -xtime.tv_sec, -xtime.tv_nsec);

#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
printk("Calibrating CPU frequency ");
@@ -48,12 +64,7 @@ void __init time_init(void)
printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
(int)(ccount_per_jiffy/(10000/HZ))%100);
#endif
-
- xtime.tv_nsec = 0;
- xtime.tv_sec = read_persistent_clock();
-
- set_normalized_timespec(&wall_to_monotonic,
- -xtime.tv_sec, -xtime.tv_nsec);
+ clocksource_register(&ccount_clocksource);

/* Initialize the linux timer interrupt. */

@@ -61,69 +72,6 @@ void __init time_init(void)
set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
}

-
-int do_settimeofday(struct timespec *tv)
-{
- time_t wtm_sec, sec = tv->tv_sec;
- long wtm_nsec, nsec = tv->tv_nsec;
- unsigned long delta;
-
- 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 then undo it!
- */
-
- delta = CCOUNT_PER_JIFFY;
- delta += get_ccount() - get_linux_timer();
- nsec -= delta * NSEC_PER_CCOUNT;
-
- 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);
-
- ntp_clear();
- write_sequnlock_irq(&xtime_lock);
- return 0;
-}
-
-EXPORT_SYMBOL(do_settimeofday);
-
-
-void do_gettimeofday(struct timeval *tv)
-{
- unsigned long flags;
- unsigned long volatile sec, usec, delta, seq;
-
- do {
- seq = read_seqbegin_irqsave(&xtime_lock, flags);
-
- sec = xtime.tv_sec;
- usec = (xtime.tv_nsec / NSEC_PER_USEC);
-
- delta = get_linux_timer() - get_ccount();
-
- } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
-
- usec += (((unsigned long) CCOUNT_PER_JIFFY - delta)
- * (unsigned long) NSEC_PER_CCOUNT) / NSEC_PER_USEC;
-
- for (; usec >= 1000000; sec++, usec -= 1000000)
- ;
-
- tv->tv_sec = sec;
- tv->tv_usec = usec;
-}
-
-EXPORT_SYMBOL(do_gettimeofday);
-
/*
* The timer interrupt is called HZ times per second.
*/
--



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