powerpc: Fix delay functions for 601 processors

My earlier merge of delay.h introduced a timebase-based udelay for
32-bit machines but also broke the 601, which doesn't have the
timebase register.  This fixes it by using the 601's RTC register on
the 601, and also moves __delay() and udelay() to be out-of-line in
arch/powerpc/kernel/time.c.  These functions aren't really performance
critical, after all.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/misc_32.S

@@ -27,14 +27,6 @@
 
 	.text
 
-	.align	5
-_GLOBAL(__delay)
-	cmpwi	0,r3,0
-	mtctr	r3
-	beqlr
-1:	bdnz	1b
-	blr
-
 /*
  * This returns the high 64 bits of the product of two 64-bit numbers.
  */

arch/powerpc/kernel/time.c

@@ -130,6 +130,34 @@ unsigned long tb_last_stamp;
  */
 DEFINE_PER_CPU(unsigned long, last_jiffy);
 
+void __delay(unsigned long loops)
+{
+	unsigned long start;
+	int diff;
+
+	if (__USE_RTC()) {
+		start = get_rtcl();
+		do {
+			/* the RTCL register wraps at 1000000000 */
+			diff = get_rtcl() - start;
+			if (diff < 0)
+				diff += 1000000000;
+		} while (diff < loops);
+	} else {
+		start = get_tbl();
+		while (get_tbl() - start < loops)
+			HMT_low();
+		HMT_medium();
+	}
+}
+EXPORT_SYMBOL(__delay);
+
+void udelay(unsigned long usecs)
+{
+	__delay(tb_ticks_per_usec * usecs);
+}
+EXPORT_SYMBOL(udelay);
+
 static __inline__ void timer_check_rtc(void)
 {
         /*

include/asm-powerpc/delay.h

@@ -13,43 +13,7 @@
  * Anton Blanchard.
  */
 
-extern unsigned long tb_ticks_per_usec;
-
-#ifdef CONFIG_PPC64
-/* define these here to prevent circular dependencies */
-/* these instructions control the thread priority on multi-threaded cpus */
-#define __HMT_low()	asm volatile("or 1,1,1")
-#define __HMT_medium()	asm volatile("or 2,2,2")
-#else
-#define __HMT_low()
-#define __HMT_medium()
-#endif
-
-#define __barrier()	asm volatile("" ::: "memory")
-
-static inline unsigned long __get_tb(void)
-{
-	unsigned long rval;
-
-	asm volatile("mftb %0" : "=r" (rval));
-	return rval;
-}
-
-static inline void __delay(unsigned long loops)
-{
-	unsigned long start = __get_tb();
-
-	while((__get_tb() - start) < loops)
-		__HMT_low();
-	__HMT_medium();
-	__barrier();
-}
-
-static inline void udelay(unsigned long usecs)
-{
-	unsigned long loops = tb_ticks_per_usec * usecs;
-
-	__delay(loops);
-}
+extern void __delay(unsigned long loops);
+extern void udelay(unsigned long usecs);
 
 #endif /* _ASM_POWERPC_DELAY_H */