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-rw-r--r--Documentation/timers/00-INDEX10
-rw-r--r--Documentation/timers/hpet.txt300
2 files changed, 310 insertions, 0 deletions
diff --git a/Documentation/timers/00-INDEX b/Documentation/timers/00-INDEX
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100-INDEX
2 - this file
3highres.txt
4 - High resolution timers and dynamic ticks design notes
5hpet.txt
6 - High Precision Event Timer Driver for Linux
7hrtimers.txt
8 - subsystem for high-resolution kernel timers
9timer_stats.txt
10 - timer usage statistics
diff --git a/Documentation/timers/hpet.txt b/Documentation/timers/hpet.txt
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1 High Precision Event Timer Driver for Linux
2
3The High Precision Event Timer (HPET) hardware is the future replacement
4for the 8254 and Real Time Clock (RTC) periodic timer functionality.
5Each HPET can have up to 32 timers. It is possible to configure the
6first two timers as legacy replacements for 8254 and RTC periodic timers.
7A specification done by Intel and Microsoft can be found at
8<http://www.intel.com/technology/architecture/hpetspec.htm>.
9
10The driver supports detection of HPET driver allocation and initialization
11of the HPET before the driver module_init routine is called. This enables
12platform code which uses timer 0 or 1 as the main timer to intercept HPET
13initialization. An example of this initialization can be found in
14arch/i386/kernel/time_hpet.c.
15
16The driver provides two APIs which are very similar to the API found in
17the rtc.c driver. There is a user space API and a kernel space API.
18An example user space program is provided below.
19
20#include <stdio.h>
21#include <stdlib.h>
22#include <unistd.h>
23#include <fcntl.h>
24#include <string.h>
25#include <memory.h>
26#include <malloc.h>
27#include <time.h>
28#include <ctype.h>
29#include <sys/types.h>
30#include <sys/wait.h>
31#include <signal.h>
32#include <fcntl.h>
33#include <errno.h>
34#include <sys/time.h>
35#include <linux/hpet.h>
36
37
38extern void hpet_open_close(int, const char **);
39extern void hpet_info(int, const char **);
40extern void hpet_poll(int, const char **);
41extern void hpet_fasync(int, const char **);
42extern void hpet_read(int, const char **);
43
44#include <sys/poll.h>
45#include <sys/ioctl.h>
46#include <signal.h>
47
48struct hpet_command {
49 char *command;
50 void (*func)(int argc, const char ** argv);
51} hpet_command[] = {
52 {
53 "open-close",
54 hpet_open_close
55 },
56 {
57 "info",
58 hpet_info
59 },
60 {
61 "poll",
62 hpet_poll
63 },
64 {
65 "fasync",
66 hpet_fasync
67 },
68};
69
70int
71main(int argc, const char ** argv)
72{
73 int i;
74
75 argc--;
76 argv++;
77
78 if (!argc) {
79 fprintf(stderr, "-hpet: requires command\n");
80 return -1;
81 }
82
83
84 for (i = 0; i < (sizeof (hpet_command) / sizeof (hpet_command[0])); i++)
85 if (!strcmp(argv[0], hpet_command[i].command)) {
86 argc--;
87 argv++;
88 fprintf(stderr, "-hpet: executing %s\n",
89 hpet_command[i].command);
90 hpet_command[i].func(argc, argv);
91 return 0;
92 }
93
94 fprintf(stderr, "do_hpet: command %s not implemented\n", argv[0]);
95
96 return -1;
97}
98
99void
100hpet_open_close(int argc, const char **argv)
101{
102 int fd;
103
104 if (argc != 1) {
105 fprintf(stderr, "hpet_open_close: device-name\n");
106 return;
107 }
108
109 fd = open(argv[0], O_RDONLY);
110 if (fd < 0)
111 fprintf(stderr, "hpet_open_close: open failed\n");
112 else
113 close(fd);
114
115 return;
116}
117
118void
119hpet_info(int argc, const char **argv)
120{
121}
122
123void
124hpet_poll(int argc, const char **argv)
125{
126 unsigned long freq;
127 int iterations, i, fd;
128 struct pollfd pfd;
129 struct hpet_info info;
130 struct timeval stv, etv;
131 struct timezone tz;
132 long usec;
133
134 if (argc != 3) {
135 fprintf(stderr, "hpet_poll: device-name freq iterations\n");
136 return;
137 }
138
139 freq = atoi(argv[1]);
140 iterations = atoi(argv[2]);
141
142 fd = open(argv[0], O_RDONLY);
143
144 if (fd < 0) {
145 fprintf(stderr, "hpet_poll: open of %s failed\n", argv[0]);
146 return;
147 }
148
149 if (ioctl(fd, HPET_IRQFREQ, freq) < 0) {
150 fprintf(stderr, "hpet_poll: HPET_IRQFREQ failed\n");
151 goto out;
152 }
153
154 if (ioctl(fd, HPET_INFO, &info) < 0) {
155 fprintf(stderr, "hpet_poll: failed to get info\n");
156 goto out;
157 }
158
159 fprintf(stderr, "hpet_poll: info.hi_flags 0x%lx\n", info.hi_flags);
160
161 if (info.hi_flags && (ioctl(fd, HPET_EPI, 0) < 0)) {
162 fprintf(stderr, "hpet_poll: HPET_EPI failed\n");
163 goto out;
164 }
165
166 if (ioctl(fd, HPET_IE_ON, 0) < 0) {
167 fprintf(stderr, "hpet_poll, HPET_IE_ON failed\n");
168 goto out;
169 }
170
171 pfd.fd = fd;
172 pfd.events = POLLIN;
173
174 for (i = 0; i < iterations; i++) {
175 pfd.revents = 0;
176 gettimeofday(&stv, &tz);
177 if (poll(&pfd, 1, -1) < 0)
178 fprintf(stderr, "hpet_poll: poll failed\n");
179 else {
180 long data;
181
182 gettimeofday(&etv, &tz);
183 usec = stv.tv_sec * 1000000 + stv.tv_usec;
184 usec = (etv.tv_sec * 1000000 + etv.tv_usec) - usec;
185
186 fprintf(stderr,
187 "hpet_poll: expired time = 0x%lx\n", usec);
188
189 fprintf(stderr, "hpet_poll: revents = 0x%x\n",
190 pfd.revents);
191
192 if (read(fd, &data, sizeof(data)) != sizeof(data)) {
193 fprintf(stderr, "hpet_poll: read failed\n");
194 }
195 else
196 fprintf(stderr, "hpet_poll: data 0x%lx\n",
197 data);
198 }
199 }
200
201out:
202 close(fd);
203 return;
204}
205
206static int hpet_sigio_count;
207
208static void
209hpet_sigio(int val)
210{
211 fprintf(stderr, "hpet_sigio: called\n");
212 hpet_sigio_count++;
213}
214
215void
216hpet_fasync(int argc, const char **argv)
217{
218 unsigned long freq;
219 int iterations, i, fd, value;
220 sig_t oldsig;
221 struct hpet_info info;
222
223 hpet_sigio_count = 0;
224 fd = -1;
225
226 if ((oldsig = signal(SIGIO, hpet_sigio)) == SIG_ERR) {
227 fprintf(stderr, "hpet_fasync: failed to set signal handler\n");
228 return;
229 }
230
231 if (argc != 3) {
232 fprintf(stderr, "hpet_fasync: device-name freq iterations\n");
233 goto out;
234 }
235
236 fd = open(argv[0], O_RDONLY);
237
238 if (fd < 0) {
239 fprintf(stderr, "hpet_fasync: failed to open %s\n", argv[0]);
240 return;
241 }
242
243
244 if ((fcntl(fd, F_SETOWN, getpid()) == 1) ||
245 ((value = fcntl(fd, F_GETFL)) == 1) ||
246 (fcntl(fd, F_SETFL, value | O_ASYNC) == 1)) {
247 fprintf(stderr, "hpet_fasync: fcntl failed\n");
248 goto out;
249 }
250
251 freq = atoi(argv[1]);
252 iterations = atoi(argv[2]);
253
254 if (ioctl(fd, HPET_IRQFREQ, freq) < 0) {
255 fprintf(stderr, "hpet_fasync: HPET_IRQFREQ failed\n");
256 goto out;
257 }
258
259 if (ioctl(fd, HPET_INFO, &info) < 0) {
260 fprintf(stderr, "hpet_fasync: failed to get info\n");
261 goto out;
262 }
263
264 fprintf(stderr, "hpet_fasync: info.hi_flags 0x%lx\n", info.hi_flags);
265
266 if (info.hi_flags && (ioctl(fd, HPET_EPI, 0) < 0)) {
267 fprintf(stderr, "hpet_fasync: HPET_EPI failed\n");
268 goto out;
269 }
270
271 if (ioctl(fd, HPET_IE_ON, 0) < 0) {
272 fprintf(stderr, "hpet_fasync, HPET_IE_ON failed\n");
273 goto out;
274 }
275
276 for (i = 0; i < iterations; i++) {
277 (void) pause();
278 fprintf(stderr, "hpet_fasync: count = %d\n", hpet_sigio_count);
279 }
280
281out:
282 signal(SIGIO, oldsig);
283
284 if (fd >= 0)
285 close(fd);
286
287 return;
288}
289
290The kernel API has three interfaces exported from the driver:
291
292 hpet_register(struct hpet_task *tp, int periodic)
293 hpet_unregister(struct hpet_task *tp)
294 hpet_control(struct hpet_task *tp, unsigned int cmd, unsigned long arg)
295
296The kernel module using this interface fills in the ht_func and ht_data
297members of the hpet_task structure before calling hpet_register.
298hpet_control simply vectors to the hpet_ioctl routine and has the same
299commands and respective arguments as the user API. hpet_unregister
300is used to terminate usage of the HPET timer reserved by hpet_register.
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-24 05:03:53 -0500