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| author | Max Filippov <jcmvbkbc@gmail.com> | 2014-01-10 12:03:35 +0400 |
|---|---|---|
| committer | Max Filippov <jcmvbkbc@gmail.com> | 2014-01-15 00:28:11 +0400 |
| commit | 9ed82c6866e2ab671935a75ea454047e8bddb177 (patch) | |
| tree | 821e8d51935476350c2c5ab308931c7efc00676e /arch | |
| parent | 58f60c222e8d4503a4be654cbd6d4e190dc1a7d8 (diff) | |
| download | linux-9ed82c6866e2ab671935a75ea454047e8bddb177.tar.gz linux-9ed82c6866e2ab671935a75ea454047e8bddb177.tar.bz2 linux-9ed82c6866e2ab671935a75ea454047e8bddb177.zip | |
xtensa: implement ndelay
Proper ndelay implementation allows for faster IO rate with drivers that
use ndelay to access their device registers, as otherwise ndelay is
emulated with udelay.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/xtensa/include/asm/delay.h | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/arch/xtensa/include/asm/delay.h b/arch/xtensa/include/asm/delay.h index 69ba4629bed0..24304b39a5c7 100644 --- a/arch/xtensa/include/asm/delay.h +++ b/arch/xtensa/include/asm/delay.h @@ -29,8 +29,10 @@ static inline void __delay(unsigned long loops) /* Undefined function to get compile-time error */ void __bad_udelay(void); +void __bad_ndelay(void); #define __MAX_UDELAY 30000 +#define __MAX_NDELAY 30000 static inline void __udelay(unsigned long usecs) { @@ -50,4 +52,24 @@ static inline void udelay(unsigned long usec) __udelay(usec); } +static inline void __ndelay(unsigned long nsec) +{ + /* + * Inner shift makes sure multiplication doesn't overflow + * for legitimate nsec values + */ + unsigned long cycles = (nsec * (ccount_freq >> 15)) >> 15; + __delay(cycles); +} + +#define ndelay(n) ndelay(n) + +static inline void ndelay(unsigned long nsec) +{ + if (__builtin_constant_p(nsec) && nsec >= __MAX_NDELAY) + __bad_ndelay(); + else + __ndelay(nsec); +} + #endif |