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Annotation of prex-old/dev/i386/i386/delay.c, Revision 1.1.1.1

1.1       nbrk        1: /*-
                      2:  * Copyright (c) 2005-2007, Kohsuke Ohtani
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms, with or without
                      6:  * modification, are permitted provided that the following conditions
                      7:  * are met:
                      8:  * 1. Redistributions of source code must retain the above copyright
                      9:  *    notice, this list of conditions and the following disclaimer.
                     10:  * 2. Redistributions in binary form must reproduce the above copyright
                     11:  *    notice, this list of conditions and the following disclaimer in the
                     12:  *    documentation and/or other materials provided with the distribution.
                     13:  * 3. Neither the name of the author nor the names of any co-contributors
                     14:  *    may be used to endorse or promote products derived from this software
                     15:  *    without specific prior written permission.
                     16:  *
                     17:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
                     18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
                     19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
                     20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
                     21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
                     22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
                     23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
                     24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
                     25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
                     26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
                     27:  * SUCH DAMAGE.
                     28:  */
                     29:
                     30: /*
                     31:  * delay.c - driver delay routine
                     32:  */
                     33:
                     34: #include <driver.h>
                     35:
                     36: static u_long delay_count;     /* Loop count for 1ms */
                     37:
                     38: static
                     39: void delay_loop(u_long count)
                     40: {
                     41:        volatile u_int i;
                     42:
                     43:        for (i = 0; i < count; i++);
                     44: }
                     45:
                     46: /*
                     47:  * Delay micro seconds (non-blocking)
                     48:  * timer_udelay() can be called from ISR at interrupt level.
                     49:  */
                     50: void
                     51: delay_usec(u_long usec)
                     52: {
                     53:
                     54:        delay_loop(delay_count * usec / 1000);
                     55: }
                     56:
                     57: /*
                     58:  * Compute the loop count for 1ms.
                     59:  * Assumes clock interrupt is enabled.
                     60:  */
                     61: void
                     62: calibrate_delay(void)
                     63: {
                     64:        u_long ticks, test_bit;
                     65:
                     66:        printk("Calibrating delay loop... ");
                     67:        delay_count = 1;
                     68:        for (;;) {
                     69:                delay_count <<= 1;
                     70:
                     71:                ticks = timer_count();
                     72:                while (ticks == timer_count());
                     73:
                     74:                ticks = timer_count();
                     75:                delay_loop(delay_count);
                     76:                if (ticks != timer_count())
                     77:                        break;
                     78:        }
                     79:        delay_count >>= 1;
                     80:        test_bit = delay_count;
                     81:
                     82:        for (;;) {
                     83:                test_bit >>= 1;
                     84:                if (test_bit == 0)
                     85:                        break;
                     86:                delay_count |= test_bit;
                     87:
                     88:                ticks = timer_count();
                     89:                while (ticks == timer_count());
                     90:
                     91:                ticks = timer_count();
                     92:                delay_loop(delay_count);
                     93:                if (ticks != timer_count())
                     94:                        delay_count &= ~test_bit;
                     95:        }
                     96:        delay_count *= 1000;    /* count per 1sec */
                     97:        delay_count /= 1000;    /* count per 1ms */
                     98:        printk("ok count=%d\n", delay_count);
                     99: }