diff options
| -rw-r--r-- | hw/ds1338.c | 59 |
1 files changed, 42 insertions, 17 deletions
diff --git a/hw/ds1338.c b/hw/ds1338.c index be68140ae2..842d2de14d 100644 --- a/hw/ds1338.c +++ b/hw/ds1338.c @@ -26,27 +26,52 @@ typedef struct { int addr_byte; } DS1338State; +static void capture_current_time(DS1338State *s) +{ + /* Capture the current time into the secondary registers + * which will be actually read by the data transfer operation. + */ + qemu_get_timedate(&s->now, s->offset); + s->nvram[0] = to_bcd(s->now.tm_sec); + s->nvram[1] = to_bcd(s->now.tm_min); + if (s->nvram[2] & 0x40) { + s->nvram[2] = (to_bcd((s->now.tm_hour % 12)) + 1) | 0x40; + if (s->now.tm_hour >= 12) { + s->nvram[2] |= 0x20; + } + } else { + s->nvram[2] = to_bcd(s->now.tm_hour); + } + s->nvram[3] = to_bcd(s->now.tm_wday) + 1; + s->nvram[4] = to_bcd(s->now.tm_mday); + s->nvram[5] = to_bcd(s->now.tm_mon) + 1; + s->nvram[6] = to_bcd(s->now.tm_year - 100); +} + +static void inc_regptr(DS1338State *s) +{ + /* The register pointer wraps around after 0x3F; wraparound + * causes the current time/date to be retransferred into + * the secondary registers. + */ + s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1); + if (!s->ptr) { + capture_current_time(s); + } +} + static void ds1338_event(I2CSlave *i2c, enum i2c_event event) { DS1338State *s = FROM_I2C_SLAVE(DS1338State, i2c); switch (event) { case I2C_START_RECV: - qemu_get_timedate(&s->now, s->offset); - s->nvram[0] = to_bcd(s->now.tm_sec); - s->nvram[1] = to_bcd(s->now.tm_min); - if (s->nvram[2] & 0x40) { - s->nvram[2] = (to_bcd((s->now.tm_hour % 12)) + 1) | 0x40; - if (s->now.tm_hour >= 12) { - s->nvram[2] |= 0x20; - } - } else { - s->nvram[2] = to_bcd(s->now.tm_hour); - } - s->nvram[3] = to_bcd(s->now.tm_wday) + 1; - s->nvram[4] = to_bcd(s->now.tm_mday); - s->nvram[5] = to_bcd(s->now.tm_mon) + 1; - s->nvram[6] = to_bcd(s->now.tm_year - 100); + /* In h/w, capture happens on any START condition, not just a + * START_RECV, but there is no need to actually capture on + * START_SEND, because the guest can't get at that data + * without going through a START_RECV which would overwrite it. + */ + capture_current_time(s); break; case I2C_START_SEND: s->addr_byte = 1; @@ -62,7 +87,7 @@ static int ds1338_recv(I2CSlave *i2c) uint8_t res; res = s->nvram[s->ptr]; - s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1); + inc_regptr(s); return res; } @@ -116,7 +141,7 @@ static int ds1338_send(I2CSlave *i2c, uint8_t data) } else { s->nvram[s->ptr] = data; } - s->ptr = (s->ptr + 1) & (NVRAM_SIZE - 1); + inc_regptr(s); return 0; } |