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author | Paul Mackerras <paulus@samba.org> | 2007-10-31 11:25:35 (GMT) |
---|---|---|
committer | Paul Mackerras <paulus@samba.org> | 2007-11-08 03:15:31 (GMT) |
commit | 43875cc0a54d936132010e58545269e183741fae (patch) | |
tree | 65409e7b9161fcaf8a88b67ebe91ffdb2ad97809 /arch/powerpc | |
parent | 465ccab9eb8209a2a402710b24a9bff127b25b94 (diff) | |
download | linux-fsl-qoriq-43875cc0a54d936132010e58545269e183741fae.tar.xz |
[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/powerpc')
-rw-r--r-- | arch/powerpc/kernel/time.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 9eb3284..99ebcd3 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; if (now <= DECREMENTER_MAX) - set_dec((unsigned int)now - 1); + set_dec((int)now); return; } old_regs = set_irq_regs(regs); @@ -611,8 +611,6 @@ void timer_interrupt(struct pt_regs * regs) if (evt->event_handler) evt->event_handler(evt); - else - evt->set_next_event(DECREMENTER_MAX, evt); #ifdef CONFIG_PPC_ISERIES 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; set_dec(evt); return 0; } @@ -871,7 +866,8 @@ void init_decrementer_clockevent(void) decrementer_clockevent.shift); 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); register_decrementer_clockevent(cpu); } |