From f41b89ed1731e50edc5da100c0a5d8a0ba3b66b1 Mon Sep 17 00:00:00 2001
From: Michael Schmitz <schmitz@xxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
