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This commit is contained in:
Warner Losh 2012-10-07 02:08:19 +00:00
parent 6859e74003
commit 71d97412d0
1 changed files with 11 additions and 6 deletions
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17
sys/arm/at91/at91_rtc.c
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@ -29,11 +29,13 @@
*
* This driver does not currently support alarms, just date and time.
*
* Note that on an rm9200 the RTC is not your typical battery-driven clock that
* keeps time while the system is powered down. In fact, it doesn't even
* survive a chip reset to keep time across a reboot. About the only thing it
* might be good for is keeping time while the cpu clock is turned off for power
* savings. On later chips, a battery backup feature is available.
* The RTC on the AT91RM9200 resets when the core rests, so it is useless as a
* source of time (except when the CPU clock is powered down to save power,
* which we don't currently do). On AT91SAM9 chips, the RTC survives chip
* reset, and there's provisions for it to keep time via battery backup if the
* system loses power. On those systems, we use it as a RTC. We tell the two
* apart because the century field is 19 on AT91RM9200 on reset, or on AT91SAM9
* chips that haven't had their time properly set.
*/
#include <sys/cdefs.h>
@ -186,10 +188,13 @@ at91_rtc_attach(device_t dev)
return (err);
}
/*
* Cannot support detach, since there's no clock_unregister function.
*/
static int
at91_rtc_detach(device_t dev)
{
return (EBUSY); /* XXX */
return (EBUSY);
}
static int