* [PATCH] HPET RTC emulation: add watchdog timer
@ 2006-01-09 15:43 Clemens Ladisch
2006-01-09 16:15 ` Clemens Ladisch
2006-01-09 16:41 ` Andi Kleen
0 siblings, 2 replies; 6+ messages in thread
From: Clemens Ladisch @ 2006-01-09 15:43 UTC (permalink / raw)
To: Andrew Morton, Venkatesh Pallipadi, Andi Kleen, Vojtech Pavlik
Cc: linux-kernel
To prevent the emulated RTC timer from stopping when interrupts are
disabled for too long, implement the watchdog timer to restart it when
needed.
Index: linux-2.6.15/arch/i386/kernel/time_hpet.c
===================================================================
--- linux-2.6.15.orig/arch/i386/kernel/time_hpet.c 2006-01-06 16:11:10.000000000 +0100
+++ linux-2.6.15/arch/i386/kernel/time_hpet.c 2006-01-08 21:31:55.000000000 +0100
@@ -413,9 +413,45 @@ int hpet_set_periodic_freq(unsigned long
int hpet_rtc_dropped_irq(void)
{
+ unsigned int cnt, ticks_per_int, lost_ints;
+
if (!is_hpet_enabled())
return 0;
+ if (UIE_on | PIE_on | AIE_on) {
+ /*
+ * The interrupt handler schedules the next interrupt at a
+ * constant offset from the time the current interrupt was
+ * scheduled, without regard to the actual time. When the
+ * handler is delayed too long, it tries to schedule the next
+ * interrupt in the past and the hardware would not interrupt
+ * until the counter had wrapped around. We catch it here.
+ */
+ cnt = hpet_readl(HPET_COUNTER);
+ /* was the comparator set to a time in the past? */
+ if ((int)(cnt - hpet_t1_cmp) > 0) {
+ /* determine how many interrupts were actually lost */
+ ticks_per_int = (hpet_tick * HZ) / hpet_rtc_int_freq;
+ lost_ints = (cnt - hpet_t1_cmp) / ticks_per_int + 1;
+ /*
+ * Make sure that, even with the time needed to execute
+ * this code, the next scheduled interrupt has been
+ * moved back to the future.
+ */
+ lost_ints++;
+
+ cnt = hpet_t1_cmp + lost_ints * ticks_per_int;
+ hpet_writel(cnt, HPET_T1_CMP);
+ hpet_t1_cmp = cnt;
+
+ if (PIE_on)
+ PIE_count += lost_ints;
+
+ printk(KERN_WARNING "rtc: lost some interrupts"
+ " at %ldHz.\n", hpet_rtc_int_freq);
+ }
+ }
+
return 1;
}
Index: linux-2.6.15/arch/x86_64/kernel/time.c
===================================================================
--- linux-2.6.15.orig/arch/x86_64/kernel/time.c 2006-01-06 16:11:13.000000000 +0100
+++ linux-2.6.15/arch/x86_64/kernel/time.c 2006-01-08 21:42:16.000000000 +0100
@@ -1234,9 +1234,45 @@ int hpet_set_periodic_freq(unsigned long
int hpet_rtc_dropped_irq(void)
{
+ unsigned int cnt, ticks_per_int, lost_ints;
+
if (!is_hpet_enabled())
return 0;
+ if (UIE_on | PIE_on | AIE_on) {
+ /*
+ * The interrupt handler schedules the next interrupt at a
+ * constant offset from the time the current interrupt was
+ * scheduled, without regard to the actual time. When the
+ * handler is delayed too long, it tries to schedule the next
+ * interrupt in the past and the hardware would not interrupt
+ * until the counter had wrapped around. We catch it here.
+ */
+ cnt = hpet_readl(HPET_COUNTER);
+ /* was the comparator set to a time in the past? */
+ if ((int)(cnt - hpet_t1_cmp) > 0) {
+ /* determine how many interrupts were actually lost */
+ ticks_per_int = (hpet_tick * HZ) / hpet_rtc_int_freq;
+ lost_ints = (cnt - hpet_t1_cmp) / ticks_per_int + 1;
+ /*
+ * Make sure that, even with the time needed to execute
+ * this code, the next scheduled interrupt has been
+ * moved back to the future.
+ */
+ lost_ints++;
+
+ cnt = hpet_t1_cmp + lost_ints * ticks_per_int;
+ hpet_writel(cnt, HPET_T1_CMP);
+ hpet_t1_cmp = cnt;
+
+ if (PIE_on)
+ PIE_count += lost_ints;
+
+ printk(KERN_WARNING "rtc: lost some interrupts"
+ " at %ldHz.\n", hpet_rtc_int_freq);
+ }
+ }
+
return 1;
}
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] HPET RTC emulation: add watchdog timer
2006-01-09 15:43 [PATCH] HPET RTC emulation: add watchdog timer Clemens Ladisch
@ 2006-01-09 16:15 ` Clemens Ladisch
2006-01-09 16:41 ` Andi Kleen
1 sibling, 0 replies; 6+ messages in thread
From: Clemens Ladisch @ 2006-01-09 16:15 UTC (permalink / raw)
To: Andrew Morton, Venkatesh Pallipadi, Andi Kleen, Vojtech Pavlik
Cc: linux-kernel
OK, this time with Signed-off line ...
To prevent the emulated RTC timer from stopping when interrupts are
disabled for too long, implement the watchdog timer to restart it when
needed.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Index: linux-2.6.15/arch/i386/kernel/time_hpet.c
===================================================================
--- linux-2.6.15.orig/arch/i386/kernel/time_hpet.c 2006-01-06 16:11:10.000000000 +0100
+++ linux-2.6.15/arch/i386/kernel/time_hpet.c 2006-01-08 21:31:55.000000000 +0100
@@ -413,9 +413,45 @@ int hpet_set_periodic_freq(unsigned long
int hpet_rtc_dropped_irq(void)
{
+ unsigned int cnt, ticks_per_int, lost_ints;
+
if (!is_hpet_enabled())
return 0;
+ if (UIE_on | PIE_on | AIE_on) {
+ /*
+ * The interrupt handler schedules the next interrupt at a
+ * constant offset from the time the current interrupt was
+ * scheduled, without regard to the actual time. When the
+ * handler is delayed too long, it tries to schedule the next
+ * interrupt in the past and the hardware would not interrupt
+ * until the counter had wrapped around. We catch it here.
+ */
+ cnt = hpet_readl(HPET_COUNTER);
+ /* was the comparator set to a time in the past? */
+ if ((int)(cnt - hpet_t1_cmp) > 0) {
+ /* determine how many interrupts were actually lost */
+ ticks_per_int = (hpet_tick * HZ) / hpet_rtc_int_freq;
+ lost_ints = (cnt - hpet_t1_cmp) / ticks_per_int + 1;
+ /*
+ * Make sure that, even with the time needed to execute
+ * this code, the next scheduled interrupt has been
+ * moved back to the future.
+ */
+ lost_ints++;
+
+ cnt = hpet_t1_cmp + lost_ints * ticks_per_int;
+ hpet_writel(cnt, HPET_T1_CMP);
+ hpet_t1_cmp = cnt;
+
+ if (PIE_on)
+ PIE_count += lost_ints;
+
+ printk(KERN_WARNING "rtc: lost some interrupts"
+ " at %ldHz.\n", hpet_rtc_int_freq);
+ }
+ }
+
return 1;
}
Index: linux-2.6.15/arch/x86_64/kernel/time.c
===================================================================
--- linux-2.6.15.orig/arch/x86_64/kernel/time.c 2006-01-06 16:11:13.000000000 +0100
+++ linux-2.6.15/arch/x86_64/kernel/time.c 2006-01-08 21:42:16.000000000 +0100
@@ -1234,9 +1234,45 @@ int hpet_set_periodic_freq(unsigned long
int hpet_rtc_dropped_irq(void)
{
+ unsigned int cnt, ticks_per_int, lost_ints;
+
if (!is_hpet_enabled())
return 0;
+ if (UIE_on | PIE_on | AIE_on) {
+ /*
+ * The interrupt handler schedules the next interrupt at a
+ * constant offset from the time the current interrupt was
+ * scheduled, without regard to the actual time. When the
+ * handler is delayed too long, it tries to schedule the next
+ * interrupt in the past and the hardware would not interrupt
+ * until the counter had wrapped around. We catch it here.
+ */
+ cnt = hpet_readl(HPET_COUNTER);
+ /* was the comparator set to a time in the past? */
+ if ((int)(cnt - hpet_t1_cmp) > 0) {
+ /* determine how many interrupts were actually lost */
+ ticks_per_int = (hpet_tick * HZ) / hpet_rtc_int_freq;
+ lost_ints = (cnt - hpet_t1_cmp) / ticks_per_int + 1;
+ /*
+ * Make sure that, even with the time needed to execute
+ * this code, the next scheduled interrupt has been
+ * moved back to the future.
+ */
+ lost_ints++;
+
+ cnt = hpet_t1_cmp + lost_ints * ticks_per_int;
+ hpet_writel(cnt, HPET_T1_CMP);
+ hpet_t1_cmp = cnt;
+
+ if (PIE_on)
+ PIE_count += lost_ints;
+
+ printk(KERN_WARNING "rtc: lost some interrupts"
+ " at %ldHz.\n", hpet_rtc_int_freq);
+ }
+ }
+
return 1;
}
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] HPET RTC emulation: add watchdog timer
2006-01-09 15:43 [PATCH] HPET RTC emulation: add watchdog timer Clemens Ladisch
2006-01-09 16:15 ` Clemens Ladisch
@ 2006-01-09 16:41 ` Andi Kleen
2006-01-09 18:00 ` lkml
1 sibling, 1 reply; 6+ messages in thread
From: Andi Kleen @ 2006-01-09 16:41 UTC (permalink / raw)
To: Clemens Ladisch
Cc: Andrew Morton, Venkatesh Pallipadi, Vojtech Pavlik, linux-kernel
On Mon, Jan 09, 2006 at 04:43:50PM +0100, Clemens Ladisch wrote:
> To prevent the emulated RTC timer from stopping when interrupts are
> disabled for too long, implement the watchdog timer to restart it when
> needed.
The interrupt handler should just read the time (it likely
has to do that anyways) and check for that
directly. That is what I did in my noidletick HPET patch and it
worked ok.
-Andi
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] HPET RTC emulation: add watchdog timer
2006-01-09 16:41 ` Andi Kleen
@ 2006-01-09 18:00 ` lkml
2006-01-09 20:32 ` Andi Kleen
0 siblings, 1 reply; 6+ messages in thread
From: lkml @ 2006-01-09 18:00 UTC (permalink / raw)
To: Andi Kleen
Cc: Clemens Ladisch, Andrew Morton, Venkatesh Pallipadi,
Vojtech Pavlik, linux-kernel
Andi Kleen wrote:
> On Mon, Jan 09, 2006 at 04:43:50PM +0100, Clemens Ladisch wrote:
> > To prevent the emulated RTC timer from stopping when interrupts
> > are disabled for too long, implement the watchdog timer to
> > restart it when needed.
>
> The interrupt handler should just read the time (it likely
> has to do that anyways)
Not in the current implementation.
> and check for that directly.
I want to avoid the read altogether because the round trip to the
south bridge is rather slow (1.5 microseconds with VIA chipsets).
Clemens
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] HPET RTC emulation: add watchdog timer
2006-01-09 18:00 ` lkml
@ 2006-01-09 20:32 ` Andi Kleen
2006-01-10 8:27 ` Clemens Ladisch
0 siblings, 1 reply; 6+ messages in thread
From: Andi Kleen @ 2006-01-09 20:32 UTC (permalink / raw)
To: lkml
Cc: Clemens Ladisch, Andrew Morton, Venkatesh Pallipadi,
Vojtech Pavlik, linux-kernel
On Mon, Jan 09, 2006 at 07:00:34PM +0100, lkml@cl.domainfactory-kunde.de wrote:
> Andi Kleen wrote:
> > On Mon, Jan 09, 2006 at 04:43:50PM +0100, Clemens Ladisch wrote:
> > > To prevent the emulated RTC timer from stopping when interrupts
> > > are disabled for too long, implement the watchdog timer to
> > > restart it when needed.
> >
> > The interrupt handler should just read the time (it likely
> > has to do that anyways)
>
> Not in the current implementation.
The standard HPET interrupt in x86-64 does this already at least.
> > and check for that directly.
>
> I want to avoid the read altogether because the round trip to the
> south bridge is rather slow (1.5 microseconds with VIA chipsets).
You can use the TSC to detect it too, but it might be unreliable.
-Andi
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] HPET RTC emulation: add watchdog timer
2006-01-09 20:32 ` Andi Kleen
@ 2006-01-10 8:27 ` Clemens Ladisch
0 siblings, 0 replies; 6+ messages in thread
From: Clemens Ladisch @ 2006-01-10 8:27 UTC (permalink / raw)
To: Andi Kleen
Cc: Andrew Morton, Venkatesh Pallipadi, Vojtech Pavlik, linux-kernel
Andi Kleen wrote:
> Clemens Ladisch <lkml@cl.domainfactory-kunde.de> wrote:
> > Andi Kleen wrote:
> > > Clemens Ladisch wrote:
> > > > To prevent the emulated RTC timer from stopping when
> > > > interrupts are disabled for too long, implement the watchdog
> > > > timer to restart it when needed.
> > >
> > > The interrupt handler should just read the time (it likely
> > > has to do that anyways)
> >
> > Not in the current implementation.
>
> The standard HPET interrupt in x86-64 does this already at least.
But it's slower than just doing a mod_timer which the RTC code does
_anyway_, so we could just as well use it. Especially as the watchdog
timer isn't actually expected to run in normal circumstances.
Clemens
^ permalink raw reply [flat|nested] 6+ messages in thread
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2006-01-09 15:43 [PATCH] HPET RTC emulation: add watchdog timer Clemens Ladisch
2006-01-09 16:15 ` Clemens Ladisch
2006-01-09 16:41 ` Andi Kleen
2006-01-09 18:00 ` lkml
2006-01-09 20:32 ` Andi Kleen
2006-01-10 8:27 ` Clemens Ladisch
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