root / prex-0.9.0 / bsp / drv / lib / delay.c @ 03e9c04a
History | View | Annotate | Download (2.78 KB)
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 |
#ifdef DEBUG
|
37 |
#define DPRINTF(a) printf a
|
38 |
#else
|
39 |
#define DPRINTF(a)
|
40 |
#endif
|
41 |
|
42 |
static u_long delay_count; /* Loop count for 1ms */ |
43 |
|
44 |
static
|
45 |
void delay_loop(u_long count)
|
46 |
{ |
47 |
volatile u_long i;
|
48 |
|
49 |
for (i = 0; i < count; i++); |
50 |
} |
51 |
|
52 |
/*
|
53 |
* Delay micro seconds (non-blocking)
|
54 |
* timer_udelay() can be called from ISR at interrupt level.
|
55 |
*/
|
56 |
void
|
57 |
delay_usec(u_long usec) |
58 |
{ |
59 |
|
60 |
delay_loop(delay_count * usec / 1000);
|
61 |
} |
62 |
|
63 |
/*
|
64 |
* Compute the loop count for 1ms.
|
65 |
* Assumes clock interrupt is enabled.
|
66 |
*/
|
67 |
void
|
68 |
calibrate_delay(void)
|
69 |
{ |
70 |
u_long ticks, test_bit; |
71 |
|
72 |
DPRINTF(("Calibrating delay loop... "));
|
73 |
delay_count = 1;
|
74 |
for (;;) {
|
75 |
delay_count <<= 1;
|
76 |
|
77 |
ticks = timer_ticks(); |
78 |
while (ticks == timer_ticks());
|
79 |
|
80 |
ticks = timer_ticks(); |
81 |
delay_loop(delay_count); |
82 |
if (ticks != timer_ticks())
|
83 |
break;
|
84 |
} |
85 |
delay_count >>= 1;
|
86 |
test_bit = delay_count; |
87 |
|
88 |
for (;;) {
|
89 |
test_bit >>= 1;
|
90 |
if (test_bit == 0) |
91 |
break;
|
92 |
delay_count |= test_bit; |
93 |
|
94 |
ticks = timer_ticks(); |
95 |
while (ticks == timer_ticks());
|
96 |
|
97 |
ticks = timer_ticks(); |
98 |
delay_loop(delay_count); |
99 |
if (ticks != timer_ticks())
|
100 |
delay_count &= ~test_bit; |
101 |
} |
102 |
delay_count *= 1000; /* count per 1sec */ |
103 |
delay_count /= 1000; /* count per 1ms */ |
104 |
DPRINTF(("ok count=%ld\n", delay_count));
|
105 |
} |