Add rtc reset function.

On reset:
Periodic Interrupt Enable (PIE) bit is cleared to zero
Alarm Interrupt Enable (AIE) bit is cleared to zero
Update ended Interrupt Flag (UF) bit is cleared to zero
Interrupt Request status Flag (IRQF) bit is cleared to zero
Periodic Interrupt Flag (PF) bit is cleared to zero
Alarm Interrupt Flag (AF) bit is cleared to zero
Square Wave output Enable (SQWE) zero
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/mc146818rtc.c

@@ -568,6 +568,22 @@ static int rtc_load_td(QEMUFile *f, void *opaque, int version_id)
 }
 #endif
 
+static void rtc_reset(void *opaque)
+{
+    RTCState *s = opaque;
+
+    /* clear PIE,AIE,SQWE on reset */
+    s->cmos_data[RTC_REG_B] &= ~((1<<6) | (1<<5) | (1<<3));
+
+    /* clear UF,IRQF,PF,AF on reset */
+    s->cmos_data[RTC_REG_C] &= ~((1<<4) | (1<<7) | (1<<6) | (1<<5));
+
+#ifdef TARGET_I386
+    if (rtc_td_hack)
+	    s->irq_coalesced = 0;
+#endif
+}
+
 RTCState *rtc_init_sqw(int base, qemu_irq irq, qemu_irq sqw_irq, int base_year)
 {
     RTCState *s;
@@ -606,6 +622,8 @@ RTCState *rtc_init_sqw(int base, qemu_irq irq, qemu_irq sqw_irq, int base_year)
     if (rtc_td_hack)
         register_savevm("mc146818rtc-td", base, 1, rtc_save_td, rtc_load_td, s);
 #endif
+    qemu_register_reset(rtc_reset, 0, s);
+
     return s;
 }
 
@@ -721,5 +739,6 @@ RTCState *rtc_mm_init(target_phys_addr_t base, int it_shift, qemu_irq irq,
     if (rtc_td_hack)
         register_savevm("mc146818rtc-td", base, 1, rtc_save_td, rtc_load_td, s);
 #endif
+    qemu_register_reset(rtc_reset, 0, s);
     return s;
 }