• D
    hpet: /dev/hpet - fixes and cleanup · 64a76f66
    David Brownell 提交于
    Minor /dev/hpet updates and bugfixes:
    
      * Remove dead code, mostly remnants of an incomplete/unusable
        kernel interface ... noted when addressing "sparse" warnings:
          + hpet_unregister() and a routine it calls
          + hpet_task and all references, including hpet_task_lock
          + hpet_data.hd_flags (and HPET_DATA_PLATFORM)
    
      * Correct and improve boot message:
          + displays *counter* (shared between comparators) bit width,
            not *timer* bit widths (which are often mixed)
          + relabel "timers" as "comparators"; this is less confusing,
            they are not independent like normal timers are (sigh)
          + display MHz not Hz; it's never less than 10 MHz.
    
      * Tighten and correct the userspace interface code
          + don't accidentally program comparators in 64-bit mode using
            32-bit values ... always force comparators into 32-bit mode
          + provide the correct bit definition flagging comparators with
            periodic capability ... the ABI is unchanged
    
      * Update Documentation/hpet.txt
          + be more correct and current
          + expand description a bit
          + don't mention that now-gone kernel interface
    
    Plus, add a FIXME comment for something that could cause big trouble
    on systems with more capable HPETs than at least Intel seems to ship.
    
    It seems that few folk use this userspace interface; it's not very
    usable given the general lack of HPET IRQ routing.  I'm told that
    the only real point of it any more is to mmap for fast timestamps;
    IMO that's handled better through the gettimeofday() vsyscall.
    Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
    Acked-by: NClemens Ladisch <clemens@ladisch.de>
    Signed-off-by: NIngo Molnar <mingo@elte.hu>
    64a76f66
hpet.txt 6.4 KB
		High Precision Event Timer Driver for Linux

The High Precision Event Timer (HPET) hardware follows a specification
by Intel and Microsoft which can be found at

	http://www.intel.com/technology/architecture/hpetspec.htm

Each HPET has one fixed-rate counter (at 10+ MHz, hence "High Precision")
and up to 32 comparators.  Normally three or more comparators are provided,
each of which can generate oneshot interupts and at least one of which has
additional hardware to support periodic interrupts.  The comparators are
also called "timers", which can be misleading since usually timers are
independent of each other ... these share a counter, complicating resets.

HPET devices can support two interrupt routing modes.  In one mode, the
comparators are additional interrupt sources with no particular system
role.  Many x86 BIOS writers don't route HPET interrupts at all, which
prevents use of that mode.  They support the other "legacy replacement"
mode where the first two comparators block interrupts from 8254 timers
and from the RTC.

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/x86/kernel/hpet.c.

The driver provides a userspace API which resembles the API found in the
RTC driver framework.  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;
}
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