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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>
This commit is contained in:
Paolo Bonzini 2012-10-01 14:22:07 +02:00 committed by Anthony Liguori
parent b6db4aca20
commit e67edb943f
2 changed files with 13 additions and 6 deletions
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15
hw/mc146818rtc.c
View File

@ -399,6 +399,10 @@ static void cmos_ioport_write(void *opaque, uint32_t addr, uint32_t data)
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 @@ static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)
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 @@ void rtc_set_memory(ISADevice *dev, int addr, int val)
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 @@ static void rtc_set_date_from_host(ISADevice *dev)
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)

4
hw/mc146818rtc_regs.h
View File

@ -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