[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 08/10] hvm/hpet: Prevent master clock equal to comparator while enabled
Based on the software-developers-hpet-spec-1-0a.pdf, the comparator for a periodic timer will change to the new value when it matches the master clock. The current code here uses a very standard rounding formula of "((x + y - 1) / y) * y". This is wrong because in this case you need to go to the next comparator value when "x" equals "y". Not when "x + 1" equals "y". In this case "y" is the period and "x" is the master clock. Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx> --- xen/arch/x86/hvm/hpet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/xen/arch/x86/hvm/hpet.c b/xen/arch/x86/hvm/hpet.c index 11ba2ba..28f5224 100644 --- a/xen/arch/x86/hvm/hpet.c +++ b/xen/arch/x86/hvm/hpet.c @@ -97,7 +97,7 @@ static uint64_t hpet_get_comparator(HPETState *h, unsigned int tn, if (period) { elapsed = hpet_read_maincounter(h, guest_time) + - period - 1 - comparator; + period - comparator; comparator += (elapsed / period) * period; h->hpet.comparator64[tn] = comparator; } -- 1.8.4 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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