diff options
Diffstat (limited to 'arch/m68k/include')
| -rw-r--r-- | arch/m68k/include/asm/delay.h | 23 |
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) */ |