1 files changed, 119 insertions, 63 deletions

diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index dcfaf09946ee..ae9f131b43c0 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -8,48 +8,100 @@
 #include <linux/acpi.h>
 #endif
 
-unsigned int mc146818_get_time(struct rtc_time *time)
+/*
+ * Execute a function while the UIP (Update-in-progress) bit of the RTC is
+ * unset.
+ *
+ * Warning: callback may be executed more then once.
+ */
+bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param),
+			void *param)
 {
-	unsigned char ctrl;
+	int i;
 	unsigned long flags;
-	unsigned char century = 0;
-	bool retry;
+	unsigned char seconds;
 
-#ifdef CONFIG_MACH_DECSTATION
-	unsigned int real_year;
-#endif
+	for (i = 0; i < 10; i++) {
+		spin_lock_irqsave(&rtc_lock, flags);
 
-again:
-	spin_lock_irqsave(&rtc_lock, flags);
-	/* Ensure that the RTC is accessible. Bit 6 must be 0! */
-	if (WARN_ON_ONCE((CMOS_READ(RTC_VALID) & 0x40) != 0)) {
-		spin_unlock_irqrestore(&rtc_lock, flags);
-		memset(time, 0xff, sizeof(*time));
-		return 0;
-	}
+		/*
+		 * Check whether there is an update in progress during which the
+		 * readout is unspecified. The maximum update time is ~2ms. Poll
+		 * every msec for completion.
+		 *
+		 * Store the second value before checking UIP so a long lasting
+		 * NMI which happens to hit after the UIP check cannot make
+		 * an update cycle invisible.
+		 */
+		seconds = CMOS_READ(RTC_SECONDS);
 
-	/*
-	 * Check whether there is an update in progress during which the
-	 * readout is unspecified. The maximum update time is ~2ms. Poll
-	 * every msec for completion.
-	 *
-	 * Store the second value before checking UIP so a long lasting NMI
-	 * which happens to hit after the UIP check cannot make an update
-	 * cycle invisible.
-	 */
-	time->tm_sec = CMOS_READ(RTC_SECONDS);
+		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
+			spin_unlock_irqrestore(&rtc_lock, flags);
+			mdelay(1);
+			continue;
+		}
 
-	if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
-		spin_unlock_irqrestore(&rtc_lock, flags);
-		mdelay(1);
-		goto again;
-	}
+		/* Revalidate the above readout */
+		if (seconds != CMOS_READ(RTC_SECONDS)) {
+			spin_unlock_irqrestore(&rtc_lock, flags);
+			continue;
+		}
 
-	/* Revalidate the above readout */
-	if (time->tm_sec != CMOS_READ(RTC_SECONDS)) {
+		if (callback)
+			callback(seconds, param);
+
+		/*
+		 * Check for the UIP bit again. If it is set now then
+		 * the above values may contain garbage.
+		 */
+		if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) {
+			spin_unlock_irqrestore(&rtc_lock, flags);
+			mdelay(1);
+			continue;
+		}
+
+		/*
+		 * A NMI might have interrupted the above sequence so check
+		 * whether the seconds value has changed which indicates that
+		 * the NMI took longer than the UIP bit was set. Unlikely, but
+		 * possible and there is also virt...
+		 */
+		if (seconds != CMOS_READ(RTC_SECONDS)) {
+			spin_unlock_irqrestore(&rtc_lock, flags);
+			continue;
+		}
 		spin_unlock_irqrestore(&rtc_lock, flags);
-		goto again;
+
+		return true;
 	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(mc146818_avoid_UIP);
+
+/*
+ * If the UIP (Update-in-progress) bit of the RTC is set for more then
+ * 10ms, the RTC is apparently broken or not present.
+ */
+bool mc146818_does_rtc_work(void)
+{
+	return mc146818_avoid_UIP(NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(mc146818_does_rtc_work);
+
+struct mc146818_get_time_callback_param {
+	struct rtc_time *time;
+	unsigned char ctrl;
+#ifdef CONFIG_ACPI
+	unsigned char century;
+#endif
+#ifdef CONFIG_MACH_DECSTATION
+	unsigned int real_year;
+#endif
+};
+
+static void mc146818_get_time_callback(unsigned char seconds, void *param_in)
+{
+	struct mc146818_get_time_callback_param *p = param_in;
 
 	/*
 	 * Only the values that we read from the RTC are set. We leave
@@ -57,39 +109,39 @@ again:
 	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
 	 * by the RTC when initially set to a non-zero value.
 	 */
-	time->tm_min = CMOS_READ(RTC_MINUTES);
-	time->tm_hour = CMOS_READ(RTC_HOURS);
-	time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
-	time->tm_mon = CMOS_READ(RTC_MONTH);
-	time->tm_year = CMOS_READ(RTC_YEAR);
+	p->time->tm_sec = seconds;
+	p->time->tm_min = CMOS_READ(RTC_MINUTES);
+	p->time->tm_hour = CMOS_READ(RTC_HOURS);
+	p->time->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
+	p->time->tm_mon = CMOS_READ(RTC_MONTH);
+	p->time->tm_year = CMOS_READ(RTC_YEAR);
 #ifdef CONFIG_MACH_DECSTATION
-	real_year = CMOS_READ(RTC_DEC_YEAR);
+	p->real_year = CMOS_READ(RTC_DEC_YEAR);
 #endif
 #ifdef CONFIG_ACPI
 	if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
-	    acpi_gbl_FADT.century)
-		century = CMOS_READ(acpi_gbl_FADT.century);
+	    acpi_gbl_FADT.century) {
+		p->century = CMOS_READ(acpi_gbl_FADT.century);
+	} else {
+		p->century = 0;
+	}
 #endif
-	ctrl = CMOS_READ(RTC_CONTROL);
-	/*
-	 * Check for the UIP bit again. If it is set now then
-	 * the above values may contain garbage.
-	 */
-	retry = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
-	/*
-	 * A NMI might have interrupted the above sequence so check whether
-	 * the seconds value has changed which indicates that the NMI took
-	 * longer than the UIP bit was set. Unlikely, but possible and
-	 * there is also virt...
-	 */
-	retry |= time->tm_sec != CMOS_READ(RTC_SECONDS);
 
-	spin_unlock_irqrestore(&rtc_lock, flags);
+	p->ctrl = CMOS_READ(RTC_CONTROL);
+}
 
-	if (retry)
-		goto again;
+int mc146818_get_time(struct rtc_time *time)
+{
+	struct mc146818_get_time_callback_param p = {
+		.time = time
+	};
+
+	if (!mc146818_avoid_UIP(mc146818_get_time_callback, &p)) {
+		memset(time, 0, sizeof(*time));
+		return -EIO;
+	}
 
-	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
+	if (!(p.ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 	{
 		time->tm_sec = bcd2bin(time->tm_sec);
 		time->tm_min = bcd2bin(time->tm_min);
@@ -97,15 +149,19 @@ again:
 		time->tm_mday = bcd2bin(time->tm_mday);
 		time->tm_mon = bcd2bin(time->tm_mon);
 		time->tm_year = bcd2bin(time->tm_year);
-		century = bcd2bin(century);
+#ifdef CONFIG_ACPI
+		p.century = bcd2bin(p.century);
+#endif
 	}
 
 #ifdef CONFIG_MACH_DECSTATION
-	time->tm_year += real_year - 72;
+	time->tm_year += p.real_year - 72;
 #endif
 
-	if (century > 20)
-		time->tm_year += (century - 19) * 100;
+#ifdef CONFIG_ACPI
+	if (p.century > 19)
+		time->tm_year += (p.century - 19) * 100;
+#endif
 
 	/*
 	 * Account for differences between how the RTC uses the values
@@ -116,7 +172,7 @@ again:
 
 	time->tm_mon--;
 
-	return RTC_24H;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(mc146818_get_time);