Re: [Xen-devel] [Qemu-devel] [PATCH v3 6/6] suspend: make rtc alarm wakeup the guest.

[Gleb Natapov <gleb@xxxxxxxxxx>]

On Thu, Feb 09, 2012 at 01:00:47PM +0100, Gerd Hoffmann wrote:
> On 02/09/12 09:56, Gleb Natapov wrote:
> > On Wed, Feb 08, 2012 at 12:00:19PM +0100, Gerd Hoffmann wrote:
> >> Add a 'wakeup' property to the mc146818rtc.  It is on by default.
> >> When enabled the rtc will wake up the guest when the alarm fires.
> >>
> >> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> >> ---
> >>  hw/mc146818rtc.c |    5 +++++
> >>  1 files changed, 5 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> >> index 314ed52..3b912c6 100644
> >> --- a/hw/mc146818rtc.c
> >> +++ b/hw/mc146818rtc.c
> >> @@ -86,6 +86,7 @@ typedef struct RTCState {
> >>      uint8_t cmos_index;
> >>      struct tm current_tm;
> >>      int32_t base_year;
> >> +    uint32_t wakeup;
> >>      qemu_irq irq;
> >>      qemu_irq sqw_irq;
> >>      int it_shift;
> >> @@ -437,6 +438,9 @@ static void rtc_update_second2(void *opaque)
> >>  
> >>          s->cmos_data[RTC_REG_C] |= REG_C_AF;
> >>          if (s->cmos_data[RTC_REG_B] & REG_B_AIE) {
> >> +            if (s->wakeup) {
> >> +                qemu_system_wakeup_request();
> >> +            }
> > RTC should do wakeup only if RTC_EN bit is set pm1en.
> 
> --verbose please.  Which register, which bit?  There is no RTC_EN in
> hw/mc146818rtc.* ...
> 

Entering --verbose mode.

Here we are on ACPI territory, not RTC :) RTC just provides one input
into ACPI wakeup machinery (Figure 4-11 in ACPI spec version 4). I am
talking about ACPI_BITMASK_RT_CLOCK_ENABLE from hw/acpi.h. It is called
RTC_EN in ACPI spec (man, we should rename them back!). Spec says that
RTC alarm can wakeup the system only if RTC_EN is set in PM1x_EN
register. This way OSPM can control which events can do wakeup.
Notice that for power button wakeup BWRBTN_EN is ignored.

> Is this enable bit specifically for wakeup from suspend?
> 
No, RTC alarm can be configured to generate SCI interrupt while system
is running.

--
                        Gleb.

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