Re: [Qemu-devel] [PATCH v2 4/4] RTC:Add UIP(update in progress) check logic

[Paolo Bonzini <pbonzini@redhat.com>]

On 02/20/2012 01:25 AM, Zhang, Yang Z wrote:
> When time base is 32kHz, the update cycle takes 1984us at the end
> of every second. And the update cycle begins 244us later after UIP
> is set. So the UIP is set in 2228us at end of every second.

I think we can keep UIP set only for 244us, since our update cycle is
instantaneous.  Otherwise looks good, thanks!

Paolo

> Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
> 
> ---
>  hw/mc146818rtc.c |   26 ++++++++++++++++++++++++++
>  1 files changed, 26 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> index 2445c6b..d4be8e9 100644
> --- a/hw/mc146818rtc.c
> +++ b/hw/mc146818rtc.c
> @@ -601,6 +601,29 @@ static void rtc_calibrate_time(RTCState *s)
>      s->current_tm = *ret;
>  }
> 
> +static int update_in_progress(RTCState *s)
> +{
> +    struct timeval tv_now;
> +    int64_t host_usec, offset_usec, guest_usec;
> +
> +    if (s->cmos_data[RTC_REG_B] & REG_B_SET) {
> +        return 0;
> +    }
> +
> +    gettimeofday(&tv_now, NULL);
> +    host_usec = tv_now.tv_sec * USEC_PER_SEC + tv_now.tv_usec;
> +    offset_usec = s->offset_sec * USEC_PER_SEC + s->offset_usec;
> +    guest_usec = host_usec + offset_usec;
> +
> +    /* UIP bit will be set at last 2228us of every second.
> +     * Only consider oscillator in 32.768kHz*/
> +    if ((guest_usec % USEC_PER_SEC) >= (USEC_PER_SEC - 2228)) {
> +        return 1;
> +    }