]>
Commit | Line | Data |
---|---|---|
7006f757 UD |
1 | /* Get frequency of the system processor. powerpc/Linux version. |
2 | Copyright (C) 2000, 2001, 2005 Free Software Foundation, Inc. | |
3 | This file is part of the GNU C Library. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, write to the Free | |
17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
18 | 02111-1307 USA. */ | |
19 | ||
20 | #include <ctype.h> | |
21 | #include <fcntl.h> | |
22 | #include <string.h> | |
23 | #include <unistd.h> | |
24 | #include <libc-internal.h> | |
25 | ||
26 | ||
27 | hp_timing_t | |
28 | __get_clockfreq (void) | |
29 | { | |
30 | /* We read the information from the /proc filesystem. /proc/cpuinfo | |
31 | contains at least one line like: | |
32 | timebase : 33333333 | |
33 | We search for this line and convert the number into an integer. */ | |
34 | static hp_timing_t timebase_freq; | |
35 | hp_timing_t result = 0L; | |
36 | ||
37 | /* If this function was called before, we know the result. */ | |
38 | if (timebase_freq != 0) | |
39 | return timebase_freq; | |
40 | ||
41 | int fd = open ("/proc/cpuinfo", O_RDONLY); | |
42 | if (__builtin_expect (fd != -1, 1)) | |
43 | { | |
44 | /* The timebase will be in the 1st 1024 bytes for systems with up | |
45 | to 8 processors. If the first read returns less then 1024 | |
46 | bytes read, we have the whole cpuinfo and can start the scan. | |
47 | Otherwise we will have to read more to insure we have the | |
48 | timebase value in the scan. */ | |
49 | char buf[1024]; | |
50 | ssize_t n; | |
51 | ||
52 | n = read (fd, buf, sizeof (buf)); | |
53 | if (n == sizeof (buf)) | |
54 | { | |
55 | /* We are here because the 1st read returned exactly sizeof | |
56 | (buf) bytes. This implies that we are not at EOF and may | |
57 | not have read the timebase value yet. So we need to read | |
58 | more bytes until we know we have EOF. We copy the lower | |
59 | half of buf to the upper half and read sizeof (buf)/2 | |
60 | bytes into the lower half of buf and repeat until we | |
61 | reach EOF. We can assume that the timebase will be in | |
62 | the last 512 bytes of cpuinfo, so two 512 byte half_bufs | |
63 | will be sufficient to contain the timebase and will | |
64 | handle the case where the timebase spans the half_buf | |
65 | boundry. */ | |
66 | const ssize_t half_buf = sizeof (buf) / 2; | |
67 | while (n >= half_buf) | |
68 | { | |
69 | memcpy (buf, buf + half_buf, half_buf); | |
70 | n = read (fd, buf + half_buf, half_buf); | |
71 | } | |
72 | if (n >= 0) | |
73 | n += half_buf; | |
74 | } | |
75 | ||
76 | if (__builtin_expect (n, 1) > 0) | |
77 | { | |
78 | char *mhz = memmem (buf, n, "timebase", 7); | |
79 | ||
80 | if (__builtin_expect (mhz != NULL, 1)) | |
81 | { | |
82 | char *endp = buf + n; | |
83 | ||
84 | /* Search for the beginning of the string. */ | |
85 | while (mhz < endp && (*mhz < '0' || *mhz > '9') && *mhz != '\n') | |
86 | ++mhz; | |
87 | ||
88 | while (mhz < endp && *mhz != '\n') | |
89 | { | |
90 | if (*mhz >= '0' && *mhz <= '9') | |
91 | { | |
92 | result *= 10; | |
93 | result += *mhz - '0'; | |
94 | } | |
95 | ||
96 | ++mhz; | |
97 | } | |
98 | } | |
99 | timebase_freq = result; | |
100 | } | |
101 | close (fd); | |
102 | } | |
103 | ||
104 | return timebase_freq; | |
105 | } |