diff options
| -rw-r--r-- | hw/mc146818rtc.c | 6 | ||||
| -rw-r--r-- | tests/rtc-test.c | 40 |
2 files changed, 45 insertions, 1 deletions
diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c index 7d84ce3d74..c79fca7d68 100644 --- a/hw/mc146818rtc.c +++ b/hw/mc146818rtc.c @@ -570,7 +570,11 @@ static void rtc_update_time(RTCState *s) guest_nsec = get_guest_rtc_ns(s); guest_sec = guest_nsec / NSEC_PER_SEC; gmtime_r(&guest_sec, &ret); - rtc_set_cmos(s, &ret); + + /* Is SET flag of Register B disabled? */ + if ((s->cmos_data[RTC_REG_B] & REG_B_SET) == 0) { + rtc_set_cmos(s, &ret); + } } static int update_in_progress(RTCState *s) diff --git a/tests/rtc-test.c b/tests/rtc-test.c index 7fdc94a3de..02edbf5727 100644 --- a/tests/rtc-test.c +++ b/tests/rtc-test.c @@ -327,6 +327,45 @@ static void fuzz_registers(void) } } +static void register_b_set_flag(void) +{ + /* Enable binary-coded decimal (BCD) mode and SET flag in Register B*/ + cmos_write(RTC_REG_B, (cmos_read(RTC_REG_B) & ~REG_B_DM) | REG_B_SET); + + cmos_write(RTC_REG_A, 0x76); + cmos_write(RTC_YEAR, 0x11); + cmos_write(RTC_CENTURY, 0x20); + cmos_write(RTC_MONTH, 0x02); + cmos_write(RTC_DAY_OF_MONTH, 0x02); + cmos_write(RTC_HOURS, 0x02); + cmos_write(RTC_MINUTES, 0x04); + cmos_write(RTC_SECONDS, 0x58); + cmos_write(RTC_REG_A, 0x26); + + /* Since SET flag is still enabled, these are equality checks. */ + g_assert_cmpint(cmos_read(RTC_HOURS), ==, 0x02); + g_assert_cmpint(cmos_read(RTC_MINUTES), ==, 0x04); + g_assert_cmpint(cmos_read(RTC_SECONDS), ==, 0x58); + g_assert_cmpint(cmos_read(RTC_DAY_OF_MONTH), ==, 0x02); + g_assert_cmpint(cmos_read(RTC_MONTH), ==, 0x02); + g_assert_cmpint(cmos_read(RTC_YEAR), ==, 0x11); + g_assert_cmpint(cmos_read(RTC_CENTURY), ==, 0x20); + + /* Disable SET flag in Register B */ + cmos_write(RTC_REG_B, cmos_read(RTC_REG_B) & ~REG_B_SET); + + g_assert_cmpint(cmos_read(RTC_HOURS), ==, 0x02); + g_assert_cmpint(cmos_read(RTC_MINUTES), ==, 0x04); + + /* Since SET flag is disabled, this is an inequality check. + * We (reasonably) assume that no (sexagesimal) overflow occurs. */ + g_assert_cmpint(cmos_read(RTC_SECONDS), >=, 0x58); + g_assert_cmpint(cmos_read(RTC_DAY_OF_MONTH), ==, 0x02); + g_assert_cmpint(cmos_read(RTC_MONTH), ==, 0x02); + g_assert_cmpint(cmos_read(RTC_YEAR), ==, 0x11); + g_assert_cmpint(cmos_read(RTC_CENTURY), ==, 0x20); +} + int main(int argc, char **argv) { QTestState *s = NULL; @@ -342,6 +381,7 @@ int main(int argc, char **argv) qtest_add_func("/rtc/alarm-time", alarm_time); qtest_add_func("/rtc/set-year/20xx", set_year_20xx); qtest_add_func("/rtc/set-year/1980", set_year_1980); + qtest_add_func("/rtc/register_b_set_flag", register_b_set_flag); qtest_add_func("/rtc/fuzz-registers", fuzz_registers); ret = g_test_run(); |