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/hardwaredesign/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. 301