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imp 2012-10-07 02:08:19 +00:00
parent 1a947de79c
commit ca3e4e0819
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. * 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 * The RTC on the AT91RM9200 resets when the core rests, so it is useless as a
* keeps time while the system is powered down. In fact, it doesn't even * source of time (except when the CPU clock is powered down to save power,
* survive a chip reset to keep time across a reboot. About the only thing it * which we don't currently do). On AT91SAM9 chips, the RTC survives chip
* might be good for is keeping time while the cpu clock is turned off for power * reset, and there's provisions for it to keep time via battery backup if the
* savings. On later chips, a battery backup feature is available. * 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> #include <sys/cdefs.h>
@ -186,10 +188,13 @@ at91_rtc_attach(device_t dev)
return (err); return (err);
} }
/*
* Cannot support detach, since there's no clock_unregister function.
*/
static int static int
at91_rtc_detach(device_t dev) at91_rtc_detach(device_t dev)
{ {
return (EBUSY); /* XXX */ return (EBUSY);
} }
static int static int