acpi, acpi_piix, vt82c686: factor out PM_TMR logic

factor out PM_TMR logic. Later This will be used by ich9 acpi.
Also fixes the same bug in vt82c686.c that was fixed by the following
commits.

> commit 055479feab63607b8042bb8ebb2e0523f17cbc4e
> Author: aliguori <aliguori@c046a42c-6fe2-441c-8c8c-71466251a162>
> Date:   Wed Jan 21 16:31:20 2009 +0000
>
>     Always return latest pmsts instead of the old one (Xiantao Zhang)
>
>     It may lead to the issue when booting windows guests with acpi=1
>     if return the old pmsts.
>
>     Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
>     Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

Cc: Blue Swirl <blauwirbel@gmail.com>
Cc: Huacai Chen <zltjiangshi@gmail.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/hw/acpi.c b/hw/acpi.c
index 8071e7b..08cb126 100644
--- a/hw/acpi.c
+++ b/hw/acpi.c
@@ -197,3 +197,48 @@
     }
     return -1;
 }
+
+/* ACPI PM_TMR */
+void acpi_pm_tmr_update(ACPIPMTimer *tmr, bool enable)
+{
+    int64_t expire_time;
+
+    /* schedule a timer interruption if needed */
+    if (enable) {
+        expire_time = muldiv64(tmr->overflow_time, get_ticks_per_sec(),
+                               PM_TIMER_FREQUENCY);
+        qemu_mod_timer(tmr->timer, expire_time);
+    } else {
+        qemu_del_timer(tmr->timer);
+    }
+}
+
+void acpi_pm_tmr_calc_overflow_time(ACPIPMTimer *tmr)
+{
+    int64_t d = acpi_pm_tmr_get_clock();
+    tmr->overflow_time = (d + 0x800000LL) & ~0x7fffffLL;
+}
+
+uint32_t acpi_pm_tmr_get(ACPIPMTimer *tmr)
+{
+    uint32_t d = acpi_pm_tmr_get_clock();;
+    return d & 0xffffff;
+}
+
+static void acpi_pm_tmr_timer(void *opaque)
+{
+    ACPIPMTimer *tmr = opaque;
+    tmr->update_sci(tmr);
+}
+
+void acpi_pm_tmr_init(ACPIPMTimer *tmr, acpi_update_sci_fn update_sci)
+{
+    tmr->update_sci = update_sci;
+    tmr->timer = qemu_new_timer_ns(vm_clock, acpi_pm_tmr_timer, tmr);
+}
+
+void acpi_pm_tmr_reset(ACPIPMTimer *tmr)
+{
+    tmr->overflow_time = 0;
+    qemu_del_timer(tmr->timer);
+}