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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 15:20:36 -0700 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/hpet.txt | |
download | kernel_samsung_espresso10-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip kernel_samsung_espresso10-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz kernel_samsung_espresso10-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.bz2 |
Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/hpet.txt')
-rw-r--r-- | Documentation/hpet.txt | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/Documentation/hpet.txt b/Documentation/hpet.txt new file mode 100644 index 0000000..4e7cc8d --- /dev/null +++ b/Documentation/hpet.txt @@ -0,0 +1,298 @@ + 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 two 32 timers. It is possible +to configure the first two timers as legacy replacements for 8254 and RTC periodic. A specification +done by INTEL and Microsoft can be found at http://www.intel.com/labs/platcomp/hpet/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. + + |