9ed82c6866
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>
75 lines
1.6 KiB
C
75 lines
1.6 KiB
C
/*
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* include/asm-xtensa/delay.h
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 2001 - 2005 Tensilica Inc.
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*
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*/
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#ifndef _XTENSA_DELAY_H
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#define _XTENSA_DELAY_H
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#include <asm/timex.h>
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#include <asm/param.h>
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extern unsigned long loops_per_jiffy;
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static inline void __delay(unsigned long loops)
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{
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if (__builtin_constant_p(loops) && loops < 2)
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__asm__ __volatile__ ("nop");
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else if (loops >= 2)
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/* 2 cycles per loop. */
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__asm__ __volatile__ ("1: addi %0, %0, -2; bgeui %0, 2, 1b"
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: "+r" (loops));
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}
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/* Undefined function to get compile-time error */
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void __bad_udelay(void);
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void __bad_ndelay(void);
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#define __MAX_UDELAY 30000
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#define __MAX_NDELAY 30000
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static inline void __udelay(unsigned long usecs)
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{
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unsigned long start = get_ccount();
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unsigned long cycles = (usecs * (ccount_freq >> 15)) >> 5;
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/* Note: all variables are unsigned (can wrap around)! */
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while (((unsigned long)get_ccount()) - start < cycles)
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cpu_relax();
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}
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static inline void udelay(unsigned long usec)
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{
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if (__builtin_constant_p(usec) && usec >= __MAX_UDELAY)
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__bad_udelay();
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else
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__udelay(usec);
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}
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static inline void __ndelay(unsigned long nsec)
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{
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/*
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* Inner shift makes sure multiplication doesn't overflow
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* for legitimate nsec values
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*/
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unsigned long cycles = (nsec * (ccount_freq >> 15)) >> 15;
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__delay(cycles);
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}
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#define ndelay(n) ndelay(n)
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static inline void ndelay(unsigned long nsec)
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{
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if (__builtin_constant_p(nsec) && nsec >= __MAX_NDELAY)
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__bad_ndelay();
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else
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__ndelay(nsec);
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}
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#endif
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