[RFC PATCH 2/5] x86_64: drive set_rtc_mss from standalone timer

Chris Wright
2007-03-31T08:35:44Z

[-- Attachment #1: x86_64-use-timer-for-set_rtc_mmss.patch --]
[-- Type: text/plain, Size: 3481 bytes --]

This is how it's done on i386, and it makes one less bit
of code to trim from main_timer_handler() when converting
to clockevents.

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>
---
arch/x86_64/kernel/time.c | 68 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 52 insertions(+), 16 deletions(-)

--- linus-2.6.orig/arch/x86_64/kernel/time.c
+++ linus-2.6/arch/x86_64/kernel/time.c
@@ -81,8 +81,9 @@ EXPORT_SYMBOL(profile_pc);
* sheet for details.
*/

-static void set_rtc_mmss(unsigned long nowtime)
+static int set_rtc_mmss(unsigned long nowtime)
{
+ int retval = 0;
int real_seconds, real_minutes, cmos_minutes;
unsigned char control, freq_select;

@@ -122,6 +123,7 @@ static void set_rtc_mmss(unsigned long n
if (abs(real_minutes - cmos_minutes) >= 30) {
printk(KERN_WARNING "time.c: can't update CMOS clock "
"from %d to %d\n", cmos_minutes, real_minutes);
+ retval = -1;
} else {
BIN_TO_BCD(real_seconds);
BIN_TO_BCD(real_minutes);
@@ -141,12 +143,60 @@ static void set_rtc_mmss(unsigned long n
CMOS_WRITE(freq_select, RTC_FREQ_SELECT);

spin_unlock(&rtc_lock);
+
+ return retval;
+}
+
+static void sync_cmos_clock(unsigned long dummy);
+
+static DEFINE_TIMER(sync_cmos_timer, sync_cmos_clock, 0, 0);
+
+static void sync_cmos_clock(unsigned long dummy)
+{
+ struct timespec now, next;
+ int fail = 1;
+
+ /*
+ * If we have an externally synchronized Linux clock, then update
+ * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
+ * called as close as possible to 500 ms before the new second starts.
+ * This code is run on a timer. If the clock is set, that timer
+ * may not expire at the correct time. Thus, we adjust...
+ */
+ if (!ntp_synced())
+ /*
+ * Not synced, exit, do not restart a timer (if one is
+ * running, let it run out).
+ */
+ return;
+
+ getnstimeofday(&now);
+ if (abs(xtime.tv_nsec - 500000000) <= tick_nsec / 2)
+ fail = set_rtc_mmss(now.tv_sec);
+
+ next.tv_nsec = 500000000 - now.tv_nsec;
+ if (next.tv_nsec <= 0)
+ next.tv_nsec += NSEC_PER_SEC;
+
+ if (!fail)
+ next.tv_sec = 659;
+ else
+ next.tv_sec = 0;
+
+ if (next.tv_nsec >= NSEC_PER_SEC) {
+ next.tv_sec++;
+ next.tv_nsec -= NSEC_PER_SEC;
+ }
+ mod_timer(&sync_cmos_timer, jiffies + timespec_to_jiffies(&next));
}

+void notify_arch_cmos_timer(void)
+{
+ mod_timer(&sync_cmos_timer, jiffies + 1);
+}

void main_timer_handler(void)
{
- static unsigned long rtc_update = 0;
/*
* Here we are in the timer irq handler. We have irqs locally disabled (so we
* don't need spin_lock_irqsave()) but we don't know if the timer_bh is running
@@ -174,20 +224,6 @@ void main_timer_handler(void)
if (!using_apic_timer)
smp_local_timer_interrupt();

-/*
- * If we have an externally synchronized Linux clock, then update CMOS clock
- * accordingly every ~11 minutes. set_rtc_mmss() will be called in the jiffy
- * closest to exactly 500 ms before the next second. If the update fails, we
- * don't care, as it'll be updated on the next turn, and the problem (time way
- * off) isn't likely to go away much sooner anyway.
- */
-
- if (ntp_synced() && xtime.tv_sec > rtc_update &&
- abs(xtime.tv_nsec - 500000000) <= tick_nsec / 2) {
- set_rtc_mmss(xtime.tv_sec);
- rtc_update = xtime.tv_sec + 660;
- }
-
write_sequnlock(&xtime_lock);
}

--