parisc: make udelay() SMP-safe

PATCH New Helge Deller 1 participant 1 message Oct 23, 2013 PA-RISC architecture

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Helge Deller

author maintainer

2013-10-23 21:29 UTC #0 lore raw

PATCH 1/1 parisc: make udelay() SMP-safe

Each CPU has it's own Control Register 16 (CR16) which is used as time source for the udelay() function. But since the CR16 registers across different CPUs are not synced, we need to recalculate the loop count if we get switched away to ensure that we really delay as much time as requested.

Signed-off-by Helge Deller <[email protected]>

arch/parisc/include/asm/delay.h +10 ~~-31~~

index 912ee7e..08e58e6 100644
@@ -1,15 +1,5 @@
-#ifndef _PARISC_DELAY_H
-#define _PARISC_DELAY_H
-
-#include <asm/special_insns.h>    /* for mfctl() */
-#include <asm/processor.h> /* for boot_cpu_data */
-
-
-/*
- * Copyright (C) 1993 Linus Torvalds
- *
- * Delay routines
- */
+#ifndef _ASM_PARISC_DELAY_H
+#define _ASM_PARISC_DELAY_H
 
 static __inline__ void __delay(unsigned long loops) {
 	asm volatile(

@@ -19,25 +9,14 @@ static __inline__ void __delay(unsigned long loops) {
 		: "=r" (loops) : "0" (loops));
 }
 
-static __inline__ void __cr16_delay(unsigned long clocks) {
-	unsigned long start;
-
-	/*
-	 * Note: Due to unsigned math, cr16 rollovers shouldn't be
-	 * a problem here. However, on 32 bit, we need to make sure
-	 * we don't pass in too big a value. The current default
-	 * value of MAX_UDELAY_MS should help prevent this.
-	 */
+extern void __udelay(unsigned long usecs);
+extern void __udelay_bad(unsigned long usecs);
 
-	start = mfctl(16);
-	while ((mfctl(16) - start) < clocks)
-	    ;
+static inline void udelay(unsigned long usecs)
+{
+	if (__builtin_constant_p(usecs) && (usecs) > 20000)
+		__udelay_bad(usecs);
+	__udelay(usecs);
 }
 
-static __inline__ void __udelay(unsigned long usecs) {
-	__cr16_delay(usecs * ((unsigned long)boot_cpu_data.cpu_hz / 1000000UL));
-}
-
-#define udelay(n) __udelay(n)
-
-#endif /* defined(_PARISC_DELAY_H) */
+#endif /* _ASM_PARISC_DELAY_H */

arch/parisc/lib/Makefile +1 -1

index 5651536..8fa92b8 100644
@@ -3,6 +3,6 @@
 #
 
 lib-y	:= lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o \
-	   ucmpdi2.o
+	   ucmpdi2.o delay.o
 
 obj-y	:= iomap.o

arch/parisc/lib/delay.c new file +73 -0

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