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hw/ds1338: Recapture current time when register pointer wraps around

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The DS1338 datasheet documents that the current time is captured into
the secondary registers when the register pointer wraps round to zero
as well as at a START condition. Implement this.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Peter Maydell 2012-10-12 11:54:38 +01:00
parent ba4906a9b6
commit 35b87a8613
1 changed files with 42 additions and 17 deletions
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39
hw/ds1338.c
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@ -26,12 +26,11 @@ typedef struct {
int addr_byte;
} DS1338State;
static void ds1338_event(I2CSlave *i2c, enum i2c_event event)
static void capture_current_time(DS1338State *s)
{
DS1338State *s = FROM_I2C_SLAVE(DS1338State, i2c);
switch (event) {
case I2C_START_RECV:
/* 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);
@ -47,6 +46,32 @@ static void ds1338_event(I2CSlave *i2c, enum i2c_event event)
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:
/* 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;
}