x86: fix hpet timer reinit for x86_64
authorPavel Emelyanov <xemul@openvz.org>
Wed, 4 Feb 2009 10:40:31 +0000 (13:40 +0300)
committerIngo Molnar <mingo@elte.hu>
Thu, 5 Feb 2009 00:04:16 +0000 (01:04 +0100)
commita6a95406c676ffe4f9dee708eb404a17c69f7fdd
treed38f5d1e266024e6df16f5499609ab8711b71d27
parentb1792e367053968f2ddb48bc911d314143ce6242
x86: fix hpet timer reinit for x86_64

There's a small problem with hpet_rtc_reinit function - it checks
for the:

hpet_readl(HPET_COUNTER) - hpet_t1_cmp > 0

to continue increasing both the HPET_T1_CMP (register) and the
hpet_t1_cmp (variable).

But since the HPET_COUNTER is always 32-bit, if the hpet_t1_cmp
is 64-bit this condition will always be FALSE once the latter hits
the 32-bit boundary, and we can have a situation, when we don't
increase the HPET_T1_CMP register high enough.

The result - timer stops ticking, since HPET_T1_CMP becomes less,
than the COUNTER and never increased again.

The solution is (based on Linus's suggestion) to not compare 64-bits
(on 64-bit x86), but to do the comparison on 32-bit signed
integers.

Reported-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
arch/x86/kernel/hpet.c