delay.h

Go to the documentation of this file.

/*
 * include/asm-microblaze/delay.h
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2008 Michal Simek
 * Copyright (C) 2007 John Williams
 * Copyright (C) 2006 Atmark Techno, Inc.
 */

#ifndef _ASM_MICROBLAZE_DELAY_H
#define _ASM_MICROBLAZE_DELAY_H

extern inline void __delay(unsigned long loops)
{
    asm volatile ("# __delay        \n\t"       \
            "1: addi    %0, %0, -1\t\n"     \
            "bneid  %0, 1b      \t\n"       \
            "nop            \t\n"
            : "=r" (loops)
            : "0" (loops));
}

/*
 * Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
 * loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
 *
 * The mul instruction gives us loops = (a * b) / 2^32.
 * We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
 * because this lets us support a wide range of HZ and
 * loops_per_jiffy values without either a or b overflowing 2^32.
 * Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
 * loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
 * (which corresponds to ~3800 bogomips at HZ = 100).
 * -- paulus
 */
#define __MAX_UDELAY    (226050910UL/HZ)    /* maximum udelay argument */
#define __MAX_NDELAY    (4294967295UL/HZ)   /* maximum ndelay argument */

extern unsigned long loops_per_jiffy;

extern inline void __udelay(unsigned int x)
{

    unsigned long long tmp =
        (unsigned long long)x * (unsigned long long)loops_per_jiffy \
            * 226LL;
    unsigned loops = tmp >> 32;

/*
    __asm__("mulxuu %0,%1,%2" : "=r" (loops) :
        "r" (x), "r" (loops_per_jiffy * 226));
*/
    __delay(loops);
}

extern void __bad_udelay(void);     /* deliberately undefined */
extern void __bad_ndelay(void);     /* deliberately undefined */

#define udelay(n) (__builtin_constant_p(n) ? \
    ((n) > __MAX_UDELAY ? __bad_udelay() : __udelay((n) * (19 * HZ))) : \
    __udelay((n) * (19 * HZ)))

#define ndelay(n) (__builtin_constant_p(n) ? \
    ((n) > __MAX_NDELAY ? __bad_ndelay() : __udelay((n) * HZ)) : \
    __udelay((n) * HZ))

#define muldiv(a, b, c)     (((a)*(b))/(c))

#endif /* _ASM_MICROBLAZE_DELAY_H */