MIPS: make cp0 counter clocksource/event usable as fallback.

The current mips clock build infrastructure lets a system only use
either the MIPS cp0 counter or a SoC specific timer as a clocksource /
clockevent device.

This patch renames the core cp0 counter clocksource / clockevent functions
from mips_* to r4k_* and updates the wrappers in asm-mips/time.h to
call these renamed functions instead.

Chips which can detect whether it is safe to use a chip-specific timer
can now fall back on the cp0 counter if necessary and possible
(e.g. Alchemy with a follow-on patch).

Existing behaviour is not changed in any way.

Signed-off-by: Manuel Lauss <mano@roarinelk.homelinux.net>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -721,7 +721,11 @@ config CEVT_DS1287
 config CEVT_GT641XX
 	bool
 
+config CEVT_R4K_LIB
+	bool
+
 config CEVT_R4K
+	select CEVT_R4K_LIB
 	bool
 
 config CEVT_SB1250
@@ -736,7 +740,11 @@ config CSRC_BCM1480
 config CSRC_IOASIC
 	bool
 
+config CSRC_R4K_LIB
+	bool
+
 config CSRC_R4K
+	select CSRC_R4K_LIB
 	bool
 
 config CSRC_SB1250

arch/mips/include/asm/time.h

@@ -50,27 +50,35 @@ extern int (*perf_irq)(void);
 /*
  * Initialize the calling CPU's compare interrupt as clockevent device
  */
-#ifdef CONFIG_CEVT_R4K
-extern int mips_clockevent_init(void);
+#ifdef CONFIG_CEVT_R4K_LIB
 extern unsigned int __weak get_c0_compare_int(void);
-#else
+extern int r4k_clockevent_init(void);
+#endif
+
 static inline int mips_clockevent_init(void)
 {
+#ifdef CONFIG_CEVT_R4K
+	return r4k_clockevent_init();
+#else
 	return -ENXIO;
-}
 #endif
+}
 
 /*
  * Initialize the count register as a clocksource
  */
-#ifdef CONFIG_CSRC_R4K
-extern int init_mips_clocksource(void);
-#else
+#ifdef CONFIG_CSRC_R4K_LIB
+extern int init_r4k_clocksource(void);
+#endif
+
 static inline int init_mips_clocksource(void)
 {
+#ifdef CONFIG_CSRC_R4K
+	return init_r4k_clocksource();
+#else
 	return 0;
-}
 #endif
+}
 
 extern void clocksource_set_clock(struct clocksource *cs, unsigned int clock);
 extern void clockevent_set_clock(struct clock_event_device *cd,

arch/mips/kernel/Makefile

@@ -9,7 +9,7 @@ obj-y		+= cpu-probe.o branch.o entry.o genex.o irq.o process.o \
 		   time.o topology.o traps.o unaligned.o watch.o
 
 obj-$(CONFIG_CEVT_BCM1480)	+= cevt-bcm1480.o
-obj-$(CONFIG_CEVT_R4K)		+= cevt-r4k.o
+obj-$(CONFIG_CEVT_R4K_LIB)	+= cevt-r4k.o
 obj-$(CONFIG_MIPS_MT_SMTC)	+= cevt-smtc.o
 obj-$(CONFIG_CEVT_DS1287)	+= cevt-ds1287.o
 obj-$(CONFIG_CEVT_GT641XX)	+= cevt-gt641xx.o
@@ -17,7 +17,7 @@ obj-$(CONFIG_CEVT_SB1250)	+= cevt-sb1250.o
 obj-$(CONFIG_CEVT_TXX9)		+= cevt-txx9.o
 obj-$(CONFIG_CSRC_BCM1480)	+= csrc-bcm1480.o
 obj-$(CONFIG_CSRC_IOASIC)	+= csrc-ioasic.o
-obj-$(CONFIG_CSRC_R4K)		+= csrc-r4k.o
+obj-$(CONFIG_CSRC_R4K_LIB)	+= csrc-r4k.o
 obj-$(CONFIG_CSRC_SB1250)	+= csrc-sb1250.o
 obj-$(CONFIG_SYNC_R4K)		+= sync-r4k.o
 

arch/mips/kernel/cevt-r4k.c

@@ -160,7 +160,7 @@ int c0_compare_int_usable(void)
 
 #ifndef CONFIG_MIPS_MT_SMTC
 
-int __cpuinit mips_clockevent_init(void)
+int __cpuinit r4k_clockevent_init(void)
 {
 	uint64_t mips_freq = mips_hpt_frequency;
 	unsigned int cpu = smp_processor_id();

arch/mips/kernel/csrc-r4k.c

@@ -22,7 +22,7 @@ static struct clocksource clocksource_mips = {
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-int __init init_mips_clocksource(void)
+int __init init_r4k_clocksource(void)
 {
 	if (!cpu_has_counter || !mips_hpt_frequency)
 		return -ENXIO;