Re: [Qemu-devel] [PATCH v4 3/7] RTC: Add UIP(update in progress) check logic

[Stefano Stabellini]

On Mon, 19 Mar 2012, Zhang, Yang Z wrote:
> The UIP(update in progress) is set when RTC is updating. And the update cycle 
> begins 244us later after UIP is set. And it is cleared when update end.

this patch seems good to me


> Signed-off-by: Yang Zhang <address@hidden>
> ---
>  hw/mc146818rtc.c |   18 ++++++++++++++++++
>  1 files changed, 18 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> index 82a5b8a..6ebb8f6 100644
> --- a/hw/mc146818rtc.c
> +++ b/hw/mc146818rtc.c
> @@ -377,6 +377,21 @@ static void rtc_calibrate_time(RTCState *s)
>      s->current_tm = *ret;
>  }
> 
> +static int update_in_progress(RTCState *s)
> +{
> +    int64_t guest_usec;
> +
> +    if (s->cmos_data[RTC_REG_B] & REG_B_SET) {
> +        return 0;
> +    }
> +    guest_usec = get_guest_rtc_us(s);
> +    /* UIP bit will be set at last 244us of every second. */
> +    if ((guest_usec % USEC_PER_SEC) >= (USEC_PER_SEC - 244)) {
> +        return 1;
> +    }
> +    return 0;
> +}
> +
>  static uint32_t cmos_ioport_read(void *opaque, uint32_t addr)
>  {
>      RTCState *s = opaque;
> @@ -402,6 +417,9 @@ static uint32_t cmos_ioport_read(void *opaque, uint32_t 
> addr)
>              break;
>          case RTC_REG_A:
>              ret = s->cmos_data[s->cmos_index];
> +            if (update_in_progress(s)) {
> +                ret |= REG_A_UIP;
> +            }
>              break;
>          case RTC_REG_C:
>              ret = s->cmos_data[s->cmos_index];
> --
> 1.7.1
>