rtc: map CMOS index 0x37 to 0x32 on read and writes
QEMU's attempt to implement the century byte cover two possible places
for the byte. A common one on modern chipsets is 0x32, but QEMU also
stores the value in 0x37 (apparently for IBM PS/2 compatibility---it's
only been 25 years). To simplify the implementation of the century
byte, store it only at 0x32 but remap transparently 0x37 to 0x32 when
reading and writing from CMOS.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
index d63554f..a7d20d5 100644
--- a/hw/mc146818rtc.c
+++ b/hw/mc146818rtc.c
@@ -399,6 +399,10 @@
s->cmos_data[s->cmos_index] = data;
check_update_timer(s);
break;
+ case RTC_IBM_PS2_CENTURY_BYTE:
+ s->cmos_index = RTC_CENTURY;
+ /* fall through */
+ case RTC_CENTURY:
case RTC_SECONDS:
case RTC_MINUTES:
case RTC_HOURS:
@@ -598,6 +602,10 @@
return 0xff;
} else {
switch(s->cmos_index) {
+ case RTC_IBM_PS2_CENTURY_BYTE:
+ s->cmos_index = RTC_CENTURY;
+ /* fall through */
+ case RTC_CENTURY:
case RTC_SECONDS:
case RTC_MINUTES:
case RTC_HOURS:
@@ -661,10 +669,6 @@
s->cmos_data[addr] = val;
}
-/* PC cmos mappings */
-#define REG_IBM_CENTURY_BYTE 0x32
-#define REG_IBM_PS2_CENTURY_BYTE 0x37
-
static void rtc_set_date_from_host(ISADevice *dev)
{
RTCState *s = DO_UPCAST(RTCState, dev, dev);
@@ -681,8 +685,7 @@
rtc_set_cmos(s, &tm);
val = rtc_to_bcd(s, (tm.tm_year / 100) + 19);
- rtc_set_memory(dev, REG_IBM_CENTURY_BYTE, val);
- rtc_set_memory(dev, REG_IBM_PS2_CENTURY_BYTE, val);
+ rtc_set_memory(dev, RTC_CENTURY, val);
}
static int rtc_post_load(void *opaque, int version_id)
diff --git a/hw/mc146818rtc_regs.h b/hw/mc146818rtc_regs.h
index fc10076..ccdee42 100644
--- a/hw/mc146818rtc_regs.h
+++ b/hw/mc146818rtc_regs.h
@@ -44,6 +44,10 @@
#define RTC_REG_C 12
#define RTC_REG_D 13
+/* PC cmos mappings */
+#define RTC_CENTURY 0x32
+#define RTC_IBM_PS2_CENTURY_BYTE 0x37
+
#define REG_A_UIP 0x80
#define REG_B_SET 0x80
