Date: Sun, 7 Oct 2012 02:08:19 +0000 (UTC) From: Warner Losh <imp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r241308 - head/sys/arm/at91 Message-ID: <201210070208.q9728JT7091700@svn.freebsd.org>
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Author: imp Date: Sun Oct 7 02:08:19 2012 New Revision: 241308 URL: http://svn.freebsd.org/changeset/base/241308 Log: Improve a few comments. Modified: head/sys/arm/at91/at91_rtc.c Modified: head/sys/arm/at91/at91_rtc.c ============================================================================== --- head/sys/arm/at91/at91_rtc.c Sun Oct 7 01:58:32 2012 (r241307) +++ head/sys/arm/at91/at91_rtc.c Sun Oct 7 02:08:19 2012 (r241308) @@ -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 @@ out: 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
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