path: root/arch
diff options
authorPaul Mackerras <paulus@samba.org>2007-10-31 22:25:35 +1100
committerPaul Mackerras <paulus@samba.org>2007-11-08 14:15:31 +1100
commit43875cc0a54d936132010e58545269e183741fae (patch)
tree65409e7b9161fcaf8a88b67ebe91ffdb2ad97809 /arch
parent[POWERPC] Fix switch_slb handling of 1T ESID values (diff)
[POWERPC] Fix off-by-one error in setting decrementer on Book E/4xx (v2)
The decrementer in Book E and 4xx processors interrupts on the transition from 1 to 0, rather than on the 0 to -1 transition as on 64-bit server and 32-bit "classic" (6xx/7xx/7xxx) processors. At the moment we subtract 1 from the count of how many decrementer ticks are required before the next interrupt before putting it into the decrementer, which is correct for server/classic processors, but could possibly cause the interrupt to happen too early on Book E and 4xx if the timebase/decrementer frequency is low. This fixes the problem by making set_dec subtract 1 from the count for server and classic processors, instead of having the callers subtract 1. Since set_dec already had a bunch of ifdefs to handle different processor types, there is no net increase in ugliness. :) Note that calling set_dec(0) may not generate an interrupt on some processors. To make sure that decrementer_set_next_event always calls set_dec with an interval of at least 1 tick, we set min_delta_ns of the decrementer_clockevent to correspond to 2 ticks (2 rather than 1 to compensate for truncations in the conversions between ticks and ns). This also removes a redundant call to set the decrementer to 0x7fffffff - it was already set to that earlier in timer_interrupt. Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch')
1 files changed, 3 insertions, 7 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 9eb3284deac4..99ebcd3884d2 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -586,7 +586,7 @@ void timer_interrupt(struct pt_regs * regs)
/* not time for this event yet */
now = per_cpu(decrementer_next_tb, cpu) - now;
- set_dec((unsigned int)now - 1);
+ set_dec((int)now);
old_regs = set_irq_regs(regs);
@@ -611,8 +611,6 @@ void timer_interrupt(struct pt_regs * regs)
if (evt->event_handler)
- else
- evt->set_next_event(DECREMENTER_MAX, evt);
if (firmware_has_feature(FW_FEATURE_ISERIES) && hvlpevent_is_pending())
@@ -836,9 +834,6 @@ static int decrementer_set_next_event(unsigned long evt,
struct clock_event_device *dev)
__get_cpu_var(decrementer_next_tb) = get_tb_or_rtc() + evt;
- /* The decrementer interrupts on the 0 -> -1 transition */
- if (evt)
- --evt;
return 0;
@@ -871,7 +866,8 @@ void init_decrementer_clockevent(void)
decrementer_clockevent.max_delta_ns =
clockevent_delta2ns(DECREMENTER_MAX, &decrementer_clockevent);
- decrementer_clockevent.min_delta_ns = 1000;
+ decrementer_clockevent.min_delta_ns =
+ clockevent_delta2ns(2, &decrementer_clockevent);