Rework IP22 RTC year base computation, again. It turns out that different

Indy PROM versions use different year bases - after all, using 1970 instead
of the previously used value of 1940 smelled like a bug, and probably was,
so this eventually got fixed in later PROM versions.

Instead of hardcoding a year base depending upon the system, we will now ask
ARCBios for its current year, and compare it to what can be read from the RTC
registers to figure out what year base is in use by the PROM.

1 files changed, 31 insertions, 6 deletions

diff --git a/sys/arch/sgi/hpc/dsclock.c b/sys/arch/sgi/hpc/dsclock.c
index f1c2d05c20f..4831371da2d 100644
--- a/sys/arch/sgi/hpc/dsclock.c
+++ b/sys/arch/sgi/hpc/dsclock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dsclock.c,v 1.2 2012/04/05 21:51:55 miod Exp $	*/
+/*	$OpenBSD: dsclock.c,v 1.3 2012/04/06 19:00:49 miod Exp $	*/
 /*	$NetBSD: dsclock.c,v 1.5 2011/07/01 18:53:46 dyoung Exp $	*/
 
 /*
@@ -50,14 +50,13 @@
 #include <sgi/hpc/hpcvar.h>
 #include <sgi/sgi/ip22.h>
 
-#define	IRIX_BASE_YEAR \
-	(sys_config.system_subtype == IP22_INDY ? POSIX_BASE_YEAR : 1940)
-
 struct dsclock_softc {
 	struct device		sc_dev;
 
 	bus_space_tag_t		sc_iot;
 	bus_space_handle_t	sc_ioh;
+
+	uint			sc_base;
 };
 
 int	dsclock_match(struct device *, void *, void *);
@@ -109,6 +108,7 @@ dsclock_attach(struct device *parent, struct device *self, void *aux)
 {
 	struct dsclock_softc *sc = (void *)self;
 	struct hpc_attach_args *haa = aux;
+	ds1286_todregs regs;
 
 	sc->sc_iot = haa->ha_st;
 	if (bus_space_subregion(haa->ha_st, haa->ha_sh, haa->ha_devoff,
@@ -122,6 +122,31 @@ dsclock_attach(struct device *parent, struct device *self, void *aux)
 	sys_tod.tod_get = dsclock_gettime;
 	sys_tod.tod_set = dsclock_settime;
 	sys_tod.tod_cookie = self;
+
+	/*
+	 * Try and figure out what year the chip time is relative to.
+	 * Different Indy PROM versions appear to use different base:
+	 *  PROM Monitor SGI Version 5.1 Rev B3 IP24 Sep 17, 1993 (BE)
+	 * uses 1970, while
+	 *  PROM Monitor SGI Version 5.3 Rev B10 R4X00/R5000 IP24 Feb 12, 1996 (BE)
+	 * uses 1940.
+	 */
+
+	DS1286_GETTOD(sc, &regs);
+	sc->sc_base = bios_year - frombcd(regs[DS1286_YEAR]);
+	/* year might have changed between the ARCBios call and now... */
+	if ((sc->sc_base % 10) == 9)
+		sc->sc_base++;
+
+	/*
+	 * If the data in the chip does not make sense, assume the usual
+	 * IRIX timebase (1940 because it's a leap year).
+	 */
+	if (sc->sc_base != 1940 && sc->sc_base != POSIX_BASE_YEAR)
+		sc->sc_base = 1940;
+
+	/* mips64 clock code expects year relative to 1900 */
+	sc->sc_base -= 1900;
 }
 
 /*
@@ -158,7 +183,7 @@ dsclock_gettime(void *cookie, time_t base, struct tod_time *ct)
 
 	ct->day = frombcd(regs[DS1286_DOM]);
 	ct->mon = frombcd(regs[DS1286_MONTH] & DS1286_MONTH_MASK);
-	ct->year = frombcd(regs[DS1286_YEAR]) + (IRIX_BASE_YEAR - 1900);
+	ct->year = frombcd(regs[DS1286_YEAR]) + sc->sc_base;
 }
 
 /*
@@ -186,7 +211,7 @@ dsclock_settime(void *cookie, struct tod_time *ct)
 	regs[DS1286_MONTH] &=  ~DS1286_MONTH_MASK;
 	regs[DS1286_MONTH] |=  tobcd(ct->mon) & DS1286_MONTH_MASK;
 
-	regs[DS1286_YEAR] = tobcd(ct->year - (IRIX_BASE_YEAR - 1900));
+	regs[DS1286_YEAR] = tobcd(ct->year - sc->sc_base);
 
 	s = splhigh();
 	DS1286_PUTTOD(sc, &regs);