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Commit 9ed82c68 authored by Max Filippov's avatar Max Filippov
Browse files

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: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent 58f60c22

arch/xtensa/include/asm/delay.h

+22 −0
Original line number Diff line number Diff line
@@ -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