>From f41b89ed1731e50edc5da100c0a5d8a0ba3b66b1 Mon Sep 17 00:00:00 2001
From: Michael Schmitz <[email protected]>
Date: Wed, 23 May 2012 13:34:09 +1200
Subject: [PATCH 09/11] [m68k] Implement ndelay() based on the existing udelay()
logic (needed for ISP1160)
---
arch/m68k/include/asm/delay.h | 26 ++++++++++++++++++++++++++
1 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/arch/m68k/include/asm/delay.h b/arch/m68k/include/asm/delay.h
index 9c09bec..a37abf5 100644
--- a/arch/m68k/include/asm/delay.h
+++ b/arch/m68k/include/asm/delay.h
@@ -92,5 +92,31 @@ static inline void __udelay(unsigned long usecs)
#define udelay(n) (__builtin_constant_p(n) ? \
((n) > 20000 ? __bad_udelay() : __const_udelay(n)) : __udelay(n))
+/*
+ * nanosecond delay:
+ *
+ * ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6) is the number of loops
per microsecond
+ *
+ * 1000 / ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6) is the number
of nanoseconds per loop
+ *
+ * So n / ( 1000 / ((((HZSCALE) >> 11) * (loops_per_jiffy >> 11)) >> 6) )
would be the number of loops for n nanoseconds
+ *
+ * ndelay(n) = __delay( DIV_ROUND_UP( (n) * ((((HZSCALE) >> 11) *
(loops_per_jiffy >> 11)) >> 6), 1000 ) )
+ */
+
+
+#if defined(CONFIG_M68000) || defined(CONFIG_COLDFIRE)
+/*
+ * The simpler m68k and ColdFire processors do not have a 32*32->64
+ * multiply instruction. So we need to handle them a little differently.
+ * We use a bit of shifting and a single 32*32->32 multiply to get close.
+ * This is a macro so that the const version can factor out the first
+ * multiply and shift.
+ */
+#define HZSCALE (268435456 / (1000000 / HZ))
+
+#define ndelay(n) __delay( DIV_ROUND_UP( (n) * ((((HZSCALE) >> 11) *
(loops_per_jiffy >> 11)) >> 6), 1000 ) );
+
+#endif
#endif /* defined(_M68K_DELAY_H) */
--
1.7.0.4
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