forked from Minki/linux
f12555d24c
mdelay(1) (i.e. udelay(1000)) does not work correctly due to overflow.
1000 * 0x004189374BC6A7f0 = 0x10000000000000180 (>= 2**64)
0x004189374BC6A7ef (0x004189374BC6A7f0 - 1) is OK and it is exactly
same as catchall case (0x8000000000000000UL / (500000 / HZ)).
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
/*
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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) 1994 by Waldorf Electronics
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* Copyright (C) 1995 - 2000, 01, 03 by Ralf Baechle
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* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
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*/
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#ifndef _ASM_DELAY_H
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#define _ASM_DELAY_H
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#include <linux/config.h>
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#include <linux/param.h>
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#include <linux/smp.h>
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#include <asm/compiler.h>
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static inline void __delay(unsigned long loops)
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{
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if (sizeof(long) == 4)
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__asm__ __volatile__ (
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".set\tnoreorder\n"
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"1:\tbnez\t%0,1b\n\t"
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"subu\t%0,1\n\t"
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".set\treorder"
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: "=r" (loops)
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: "0" (loops));
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else if (sizeof(long) == 8)
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__asm__ __volatile__ (
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".set\tnoreorder\n"
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"1:\tbnez\t%0,1b\n\t"
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"dsubu\t%0,1\n\t"
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".set\treorder"
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:"=r" (loops)
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:"0" (loops));
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}
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/*
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* Division by multiplication: you don't have to worry about
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* loss of precision.
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*
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* Use only for very small delays ( < 1 msec). Should probably use a
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* lookup table, really, as the multiplications take much too long with
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* short delays. This is a "reasonable" implementation, though (and the
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* first constant multiplications gets optimized away if the delay is
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* a constant)
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*/
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static inline void __udelay(unsigned long usecs, unsigned long lpj)
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{
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unsigned long lo;
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/*
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* The rates of 128 is rounded wrongly by the catchall case
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* for 64-bit. Excessive precission? Probably ...
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*/
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#if defined(CONFIG_64BIT) && (HZ == 128)
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usecs *= 0x0008637bd05af6c7UL; /* 2**64 / (1000000 / HZ) */
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#elif defined(CONFIG_64BIT)
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usecs *= (0x8000000000000000UL / (500000 / HZ));
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#else /* 32-bit junk follows here */
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usecs *= (unsigned long) (((0x8000000000000000ULL / (500000 / HZ)) +
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0x80000000ULL) >> 32);
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#endif
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if (sizeof(long) == 4)
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__asm__("multu\t%2, %3"
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: "=h" (usecs), "=l" (lo)
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: "r" (usecs), "r" (lpj)
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: GCC_REG_ACCUM);
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else if (sizeof(long) == 8)
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__asm__("dmultu\t%2, %3"
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: "=h" (usecs), "=l" (lo)
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: "r" (usecs), "r" (lpj)
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: GCC_REG_ACCUM);
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__delay(usecs);
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}
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#define __udelay_val cpu_data[smp_processor_id()].udelay_val
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#define udelay(usecs) __udelay((usecs),__udelay_val)
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/* make sure "usecs *= ..." in udelay do not overflow. */
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#if HZ >= 1000
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#define MAX_UDELAY_MS 1
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#elif HZ <= 200
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#define MAX_UDELAY_MS 5
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#else
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#define MAX_UDELAY_MS (1000 / HZ)
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#endif
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#endif /* _ASM_DELAY_H */
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