summaryrefslogtreecommitdiffstats
path: root/Documentation/timers/hpet.txt
blob: 6ad52d9dad6cab36b4fac984aa3f39b3aba073fe (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
		High Precision Event Timer Driver for Linux

The High Precision Event Timer (HPET) hardware is the future replacement
for the 8254 and Real Time Clock (RTC) periodic timer functionality.
Each HPET can have up to 32 timers.  It is possible to configure the
first two timers as legacy replacements for 8254 and RTC periodic timers.
A specification done by Intel and Microsoft can be found at
<http://www.intel.com/technology/architecture/hpetspec.htm>.

The driver supports detection of HPET driver allocation and initialization
of the HPET before the driver module_init routine is called.  This enables
platform code which uses timer 0 or 1 as the main timer to intercept HPET
initialization.  An example of this initialization can be found in
arch/i386/kernel/time_hpet.c.

The driver provides two APIs which are very similar to the API found in
the rtc.c driver.  There is a user space API and a kernel space API.
An example user space program is provided below.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <memory.h>
#include <malloc.h>
#include <time.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/time.h>
#include <linux/hpet.h>


extern void hpet_open_close(int, const char **);
extern void hpet_info(int, const char **);
extern void hpet_poll(int, const char **);
extern void hpet_fasync(int, const char **);
extern void hpet_read(int, const char **);

#include <sys/poll.h>
#include <sys/ioctl.h>
#include <signal.h>

struct hpet_command {
	char		*command;
	void		(*func)(int argc, const char ** argv);
} hpet_command[] = {
	{
		"open-close",
		hpet_open_close
	},
	{
		"info",
		hpet_info
	},
	{
		"poll",
		hpet_poll
	},
	{
		"fasync",
		hpet_fasync
	},
};

int
main(int argc, const char ** argv)
{
	int	i;

	argc--;
	argv++;

	if (!argc) {
		fprintf(stderr, "-hpet: requires command\n");
		return -1;
	}


	for (i = 0; i < (sizeof (hpet_command) / sizeof (hpet_command[0])); i++)
		if (!strcmp(argv[0], hpet_command[i].command)) {
			argc--;
			argv++;
			fprintf(stderr, "-hpet: executing %s\n",
				hpet_command[i].command);
			hpet_command[i].func(argc, argv);
			return 0;
		}

	fprintf(stderr, "do_hpet: command %s not implemented\n", argv[0]);

	return -1;
}

void
hpet_open_close(int argc, const char **argv)
{
	int	fd;

	if (argc != 1) {
		fprintf(stderr, "hpet_open_close: device-name\n");
		return;
	}

	fd = open(argv[0], O_RDONLY);
	if (fd < 0)
		fprintf(stderr, "hpet_open_close: open failed\n");
	else
		close(fd);

	return;
}

void
hpet_info(int argc, const char **argv)
{
}

void
hpet_poll(int argc, const char **argv)
{
	unsigned long		freq;
	int			iterations, i, fd;
	struct pollfd		pfd;
	struct hpet_info	info;
	struct timeval		stv, etv;
	struct timezone		tz;
	long			usec;

	if (argc != 3) {
		fprintf(stderr, "hpet_poll: device-name freq iterations\n");
		return;
	}

	freq = atoi(argv[1]);
	iterations = atoi(argv[2]);

	fd = open(argv[0], O_RDONLY);

	if (fd < 0) {
		fprintf(stderr, "hpet_poll: open of %s failed\n", argv[0]);
		return;
	}

	if (ioctl(fd, HPET_IRQFREQ, freq) < 0) {
		fprintf(stderr, "hpet_poll: HPET_IRQFREQ failed\n");
		goto out;
	}

	if (ioctl(fd, HPET_INFO, &info) < 0) {
		fprintf(stderr, "hpet_poll: failed to get info\n");
		goto out;
	}

	fprintf(stderr, "hpet_poll: info.hi_flags 0x%lx\n", info.hi_flags);

	if (info.hi_flags && (ioctl(fd, HPET_EPI, 0) < 0)) {
		fprintf(stderr, "hpet_poll: HPET_EPI failed\n");
		goto out;
	}

	if (ioctl(fd, HPET_IE_ON, 0) < 0) {
		fprintf(stderr, "hpet_poll, HPET_IE_ON failed\n");
		goto out;
	}

	pfd.fd = fd;
	pfd.events = POLLIN;

	for (i = 0; i < iterations; i++) {
		pfd.revents = 0;
		gettimeofday(&stv, &tz);
		if (poll(&pfd, 1, -1) < 0)
			fprintf(stderr, "hpet_poll: poll failed\n");
		else {
			long 	data;

			gettimeofday(&etv, &tz);
			usec = stv.tv_sec * 1000000 + stv.tv_usec;
			usec = (etv.tv_sec * 1000000 + etv.tv_usec) - usec;

			fprintf(stderr,
				"hpet_poll: expired time = 0x%lx\n", usec);

			fprintf(stderr, "hpet_poll: revents = 0x%x\n",
				pfd.revents);

			if (read(fd, &data, sizeof(data)) != sizeof(data)) {
				fprintf(stderr, "hpet_poll: read failed\n");
			}
			else
				fprintf(stderr, "hpet_poll: data 0x%lx\n",
					data);
		}
	}

out:
	close(fd);
	return;
}

static int hpet_sigio_count;

static void
hpet_sigio(int val)
{
	fprintf(stderr, "hpet_sigio: called\n");
	hpet_sigio_count++;
}

void
hpet_fasync(int argc, const char **argv)
{
	unsigned long		freq;
	int			iterations, i, fd, value;
	sig_t			oldsig;
	struct hpet_info	info;

	hpet_sigio_count = 0;
	fd = -1;

	if ((oldsig = signal(SIGIO, hpet_sigio)) == SIG_ERR) {
		fprintf(stderr, "hpet_fasync: failed to set signal handler\n");
		return;
	}

	if (argc != 3) {
		fprintf(stderr, "hpet_fasync: device-name freq iterations\n");
		goto out;
	}

	fd = open(argv[0], O_RDONLY);

	if (fd < 0) {
		fprintf(stderr, "hpet_fasync: failed to open %s\n", argv[0]);
		return;
	}


	if ((fcntl(fd, F_SETOWN, getpid()) == 1) ||
		((value = fcntl(fd, F_GETFL)) == 1) ||
		(fcntl(fd, F_SETFL, value | O_ASYNC) == 1)) {
		fprintf(stderr, "hpet_fasync: fcntl failed\n");
		goto out;
	}

	freq = atoi(argv[1]);
	iterations = atoi(argv[2]);

	if (ioctl(fd, HPET_IRQFREQ, freq) < 0) {
		fprintf(stderr, "hpet_fasync: HPET_IRQFREQ failed\n");
		goto out;
	}

	if (ioctl(fd, HPET_INFO, &info) < 0) {
		fprintf(stderr, "hpet_fasync: failed to get info\n");
		goto out;
	}

	fprintf(stderr, "hpet_fasync: info.hi_flags 0x%lx\n", info.hi_flags);

	if (info.hi_flags && (ioctl(fd, HPET_EPI, 0) < 0)) {
		fprintf(stderr, "hpet_fasync: HPET_EPI failed\n");
		goto out;
	}

	if (ioctl(fd, HPET_IE_ON, 0) < 0) {
		fprintf(stderr, "hpet_fasync, HPET_IE_ON failed\n");
		goto out;
	}

	for (i = 0; i < iterations; i++) {
		(void) pause();
		fprintf(stderr, "hpet_fasync: count = %d\n", hpet_sigio_count);
	}

out:
	signal(SIGIO, oldsig);

	if (fd >= 0)
		close(fd);

	return;
}

The kernel API has three interfaces exported from the driver:

	hpet_register(struct hpet_task *tp, int periodic)
	hpet_unregister(struct hpet_task *tp)
	hpet_control(struct hpet_task *tp, unsigned int cmd, unsigned long arg)

The kernel module using this interface fills in the ht_func and ht_data
members of the hpet_task structure before calling hpet_register.
hpet_control simply vectors to the hpet_ioctl routine and has the same
commands and respective arguments as the user API.  hpet_unregister
is used to terminate usage of the HPET timer reserved by hpet_register.