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authorMichael Schmitz <schmitzmic@gmail.com>2013-04-06 13:26:44 +1300
committerGeert Uytterhoeven <geert@linux-m68k.org>2013-04-16 21:35:40 +0200
commitc8ee038bd14881e3ceac1cafa551f260fd0acd29 (patch)
treeadd757c501d711d1d0a8f896110a219d6137c83d /arch/m68k
parente6f80e87e05cc47188a141f68e9859ed438b4489 (diff)
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m68k: Implement ndelay() based on the existing udelay() logic
Add a ndelay macro modeled after the Coldfire udelay(). The ISP1160 driver needs a 150ns delay, so we need to have ndelay(). Signed-off-by: Michael Schmitz <schmitz@debian.org> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Diffstat (limited to 'arch/m68k')
-rw-r--r--arch/m68k/include/asm/delay.h23
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/m68k/include/asm/delay.h b/arch/m68k/include/asm/delay.h
index 12d8fe4f1d30..d28fa8fe26fe 100644
--- a/arch/m68k/include/asm/delay.h
+++ b/arch/m68k/include/asm/delay.h
@@ -92,5 +92,28 @@ 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
+ */
+
+/*
+ * 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 /* defined(_M68K_DELAY_H) */