On Thu, Jul 05, 2018 at 11:19:52AM -0700, Michael Davidsaver wrote:
> instead of a read-modify-write, do direct translation
> of device registers to struct tm members.
>
> This new ds1338_update() is the reverse of
> the existing capture_current_time().
>
> Simplifies later handling of CENTURY bit in
> similar Dallas RTC chips.
>
> Correctly handle different real weekday in
> guest and host timezones.
> Allow guest to use any day as start of week
> (day 1). eg. Monday instead of Sunday.
>
> Signed-off-by: Michael Davidsaver
> ---
> hw/timer/ds1338.c | 95
> ---
> 1 file changed, 48 insertions(+), 47 deletions(-)
>
> diff --git a/hw/timer/ds1338.c b/hw/timer/ds1338.c
> index 637a0f4246..0134ffd72a 100644
> --- a/hw/timer/ds1338.c
> +++ b/hw/timer/ds1338.c
> @@ -110,7 +110,10 @@ static void capture_current_time(DS1338State *s)
> /* 24 hour mode. */
> s->nvram[R_HOUR] = to_bcd(now.tm_hour);
> }
> -s->nvram[R_WDAY] = (now.tm_wday + s->wday_offset) % 7 + 1;
> +s->nvram[R_WDAY] = (now.tm_wday + s->wday_offset) % 7;
> +if (s->nvram[R_WDAY] == 0) {
> +s->nvram[R_WDAY] = 7;
> +}
This looks a bit odd - you've removed the + 1 here, but...
> s->nvram[R_DATE] = to_bcd(now.tm_mday);
> s->nvram[R_MONTH] = to_bcd(now.tm_mon + 1);
> s->nvram[R_YEAR] = to_bcd(now.tm_year - 100);
> @@ -161,6 +164,46 @@ static int ds1338_recv(I2CSlave *i2c)
> return res;
> }
>
> +/* call after guest writes to current time registers
> + * to re-compute our offset from host time.
> + */
> +static void ds1338_update(DS1338State *s)
> +{
> +
> +struct tm now = {};
> +
> +/* TODO: Implement CH (stop) bit? */
> +now.tm_sec = from_bcd(s->nvram[R_SEC] & 0x7f);
> +now.tm_min = from_bcd(s->nvram[R_MIN] & 0x7f);
> +if (ARRAY_FIELD_EX32(s->nvram, HOUR, SET12)) {
> +/* 12 hour (1-12) */
> +/* read and wrap 1-12 -> 0-11 */
> +now.tm_hour = from_bcd(ARRAY_FIELD_EX32(s->nvram, HOUR, HOUR12)) %
> 12u;
> +if (ARRAY_FIELD_EX32(s->nvram, HOUR, AMPM)) {
> +now.tm_hour += 12;
> +}
> +
> +} else {
> +now.tm_hour = from_bcd(ARRAY_FIELD_EX32(s->nvram, HOUR, HOUR24));
> +}
> +now.tm_wday = from_bcd(s->nvram[R_WDAY]) - 1u;
.. you still have the -1 here. Am I missing something?
> +now.tm_mday = from_bcd(s->nvram[R_DATE] & 0x3f);
> +now.tm_mon = from_bcd(s->nvram[R_MONTH] & 0x1f) - 1;
> +now.tm_year = from_bcd(s->nvram[R_YEAR]) + 100;
> +s->offset = qemu_timedate_diff();
> +
> +{
> +/* Round trip to get real wday_offset based on time delta and
> + * ref. timezone.
> + * Race if midnight (in ref. timezone) happens here.
> + */
> +int user_wday = now.tm_wday;
> +qemu_get_timedate(, s->offset);
> +
> +s->wday_offset = (user_wday - now.tm_wday) % 7 + 1;
> +}
> +}
> +
> static int ds1338_send(I2CSlave *i2c, uint8_t data)
> {
> DS1338State *s = DS1338(i2c);
> @@ -170,52 +213,7 @@ static int ds1338_send(I2CSlave *i2c, uint8_t data)
> s->addr_byte = false;
> return 0;
> }
> -if (s->ptr < 7) {
> -/* Time register. */
> -struct tm now;
> -qemu_get_timedate(, s->offset);
> -switch(s->ptr) {
> -case R_SEC:
> -/* TODO: Implement CH (stop) bit. */
> -now.tm_sec = from_bcd(data & 0x7f);
> -break;
> -case R_MIN:
> -now.tm_min = from_bcd(data & 0x7f);
> -break;
> -case R_HOUR:
> -if (FIELD_EX32(data, HOUR, SET12)) {
> -/* 12 hour (1-12) */
> -/* read and wrap 1-12 -> 0-11 */
> -now.tm_hour = from_bcd(FIELD_EX32(data, HOUR, HOUR12)) % 12u;
> -if (FIELD_EX32(data, HOUR, AMPM)) {
> -now.tm_hour += 12;
> -}
> -
> -} else {
> -now.tm_hour = from_bcd(FIELD_EX32(data, HOUR, HOUR24));
> -}
> -break;
> -case R_WDAY:
> -{
> -/* The day field is supposed to contain a value in
> - the range 1-7. Otherwise behavior is undefined.
> - */
> -int user_wday = (data & 7) - 1;
> -s->wday_offset = (user_wday - now.tm_wday + 7) % 7;
> -}
> -break;
> -case R_DATE:
> -now.tm_mday = from_bcd(data & 0x3f);
> -break;
> -case R_MONTH:
> -now.tm_mon = from_bcd(data & 0x1f) - 1;
> -break;
> -case R_YEAR:
> -now.tm_year = from_bcd(data) + 100;
> -break;
> -}
> -s->offset = qemu_timedate_diff();
> -} else if (s->ptr == R_CTRL) {
> +if (s->ptr == R_CTRL) {
> /* Control register. */
>
> /* Ensure bits 2, 3 and 6 will read back as zero. */
> @@
