x86, rtc: make CONFIG_HPET_EMULATE_RTC usable from modules

enabled, then interrupts don't work for the rtc-cmos driver which results in
RTC_AIE*, RTC_PIE* and RTC_ALM being unusable.  This affects hwclock from
util-linux-ng at least on i386 since that uses RTC_PIE_ON.  (For x86-64, a
polling method is used for unknown reasons.)

This patch series now

  1. export the functions from arch/x86/kernel/hpet.c that the old char/rtc
     driver uses to work around that problem,

  2. makes it possible to compile the old rtc driver as module, while still
     having CONFIG_HPET_EMULATE_RTC enabled and

  3. makes use of the exported functions in (1) in the new rtc-cmos driver.

This patch:

This patch makes the RTC emulation functions in arch/x86/kernel/hpet.c usable
for kernel modules. It

  - exports the functions (EXPORT_SYMBOL_GPL()),
  - adds an interface to register the interrupt callback function
    instead of using only a fixed callback function and
  - replaces the rtc_get_rtc_time() function which depends on
    CONFIG_RTC with a call to get_rtc_time() which is defined in
    include/asm-generic/rtc.h.

The only dependency to CONFIG_RTC is the call to rtc_interrupt() which is
removed by the next patch. After this, there's no (code) dependency of
this functions to CONFIG_RTC=y any more.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Cc: Andi Kleen <ak@suse.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Robert Picco <Robert.Picco@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/hpet.c

@@ -107,6 +107,7 @@ int is_hpet_enabled(void)
 {
 	return is_hpet_capable() && hpet_legacy_int_enabled;
 }
+EXPORT_SYMBOL_GPL(is_hpet_enabled);
 
 /*
  * When the hpet driver (/dev/hpet) is enabled, we need to reserve
@@ -475,6 +476,7 @@ void hpet_disable(void)
  */
 #include <linux/mc146818rtc.h>
 #include <linux/rtc.h>
+#include <asm/rtc.h>
 
 #define DEFAULT_RTC_INT_FREQ	64
 #define DEFAULT_RTC_SHIFT	6
@@ -489,6 +491,38 @@ static unsigned long hpet_default_delta;
 static unsigned long hpet_pie_delta;
 static unsigned long hpet_pie_limit;
 
+static rtc_irq_handler irq_handler;
+
+/*
+ * Registers a IRQ handler.
+ */
+int hpet_register_irq_handler(rtc_irq_handler handler)
+{
+	if (!is_hpet_enabled())
+		return -ENODEV;
+	if (irq_handler)
+		return -EBUSY;
+
+	irq_handler = handler;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hpet_register_irq_handler);
+
+/*
+ * Deregisters the IRQ handler registered with hpet_register_irq_handler()
+ * and does cleanup.
+ */
+void hpet_unregister_irq_handler(rtc_irq_handler handler)
+{
+	if (!is_hpet_enabled())
+		return;
+
+	irq_handler = NULL;
+	hpet_rtc_flags = 0;
+}
+EXPORT_SYMBOL_GPL(hpet_unregister_irq_handler);
+
 /*
  * Timer 1 for RTC emulation. We use one shot mode, as periodic mode
  * is not supported by all HPET implementations for timer 1.
@@ -530,6 +564,7 @@ int hpet_rtc_timer_init(void)
 
 	return 1;
 }
+EXPORT_SYMBOL_GPL(hpet_rtc_timer_init);
 
 /*
  * The functions below are called from rtc driver.
@@ -544,6 +579,7 @@ int hpet_mask_rtc_irq_bit(unsigned long bit_mask)
 	hpet_rtc_flags &= ~bit_mask;
 	return 1;
 }
+EXPORT_SYMBOL_GPL(hpet_mask_rtc_irq_bit);
 
 int hpet_set_rtc_irq_bit(unsigned long bit_mask)
 {
@@ -559,6 +595,7 @@ int hpet_set_rtc_irq_bit(unsigned long bit_mask)
 
 	return 1;
 }
+EXPORT_SYMBOL_GPL(hpet_set_rtc_irq_bit);
 
 int hpet_set_alarm_time(unsigned char hrs, unsigned char min,
 			unsigned char sec)
@@ -572,6 +609,7 @@ int hpet_set_alarm_time(unsigned char hrs, unsigned char min,
 
 	return 1;
 }
+EXPORT_SYMBOL_GPL(hpet_set_alarm_time);
 
 int hpet_set_periodic_freq(unsigned long freq)
 {
@@ -590,11 +628,13 @@ int hpet_set_periodic_freq(unsigned long freq)
 	}
 	return 1;
 }
+EXPORT_SYMBOL_GPL(hpet_set_periodic_freq);
 
 int hpet_rtc_dropped_irq(void)
 {
 	return is_hpet_enabled();
 }
+EXPORT_SYMBOL_GPL(hpet_rtc_dropped_irq);
 
 static void hpet_rtc_timer_reinit(void)
 {
@@ -638,9 +678,10 @@ irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
 	unsigned long rtc_int_flag = 0;
 
 	hpet_rtc_timer_reinit();
+	memset(&curr_time, 0, sizeof(struct rtc_time));
 
 	if (hpet_rtc_flags & (RTC_UIE | RTC_AIE))
-		rtc_get_rtc_time(&curr_time);
+		get_rtc_time(&curr_time);
 
 	if (hpet_rtc_flags & RTC_UIE &&
 	    curr_time.tm_sec != hpet_prev_update_sec) {
@@ -662,8 +703,12 @@ irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
 
 	if (rtc_int_flag) {
 		rtc_int_flag |= (RTC_IRQF | (RTC_NUM_INTS << 8));
+		if (irq_handler)
+			irq_handler(rtc_int_flag, dev_id);
+
 		rtc_interrupt(rtc_int_flag, dev_id);
 	}
 	return IRQ_HANDLED;
 }
+EXPORT_SYMBOL_GPL(hpet_rtc_interrupt);
 #endif

include/asm-x86/hpet.h

@@ -69,6 +69,7 @@ extern void force_hpet_resume(void);
 
 #include <linux/interrupt.h>
 
+typedef irqreturn_t (*rtc_irq_handler)(int interrupt, void *cookie);
 extern int hpet_mask_rtc_irq_bit(unsigned long bit_mask);
 extern int hpet_set_rtc_irq_bit(unsigned long bit_mask);
 extern int hpet_set_alarm_time(unsigned char hrs, unsigned char min,
@@ -77,6 +78,8 @@ extern int hpet_set_periodic_freq(unsigned long freq);
 extern int hpet_rtc_dropped_irq(void);
 extern int hpet_rtc_timer_init(void);
 extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id);
+extern int hpet_register_irq_handler(rtc_irq_handler handler);
+extern void hpet_unregister_irq_handler(rtc_irq_handler handler);
 
 #endif /* CONFIG_HPET_EMULATE_RTC */