IA-PC HPET的IA -电脑HPET (High Precision Event Timer) is a specification which was jointly developed by Intel and Microsoft in the early part of this decade.. （高精度事件定时器）是一个是由英特尔和微软共同开发了这个十年早期规范.. The latest version is dated October 2004.最新版本的日期是2004年10月。 It's stated purpose is to它的既定目的，是
initially supplement and eventually replace the legacy 8254 Programmable Interval Timer and the Real Time Clock Periodic Interrupt generation functions that are currently used as the 'de-facto' timer hardware for IA-PCs.最初补充并最终取代旧的8254可编程间隔定时器和实时时钟周期产生中断当前的'事实上的'为IA -电脑计时器硬件使用的功能。
The该 HPET HPET architecture defines a set of timers that can be used by the operating system.架构定义了可以由操作系统使用的定时器设置。 A timer block is a combination of a single counter and up to 32 comparators and match registers.计时器块是一个单一的柜台和32个组合比较和匹配寄存器。 The comparator compares the contents of the match register against the value of a free running monotonic up-counter.比较比较了反对自由运行单调了，计数器的值匹配寄存器的内容。 When the output of the up-counter equals the value in the match register an interrupt is generated.当向上计数器输出等于在比赛中值寄存器产生中断。 Each of the comparators can output an interrupt.将比较每个人都可以输出一个中断。 A maximum of 8 timer blocks are supported for a total of 256 timers.计时器的8块最多支持256个总计时器。 Each timer block can have different clocking attributes.每个定时器块可以有不同的时钟属性。 Specific implementations may include only a subset of these timers.具体的实现可能只包括这些计时器的一个子集。 A minimum of three timers is required.最低的3个定时器是必要的。
The specification contains the following block diagram of the HPET architecture.该规范包含以下HPET结构框图。
Some of the timers may be enabled to generate a periodic interrupt.对一些可能被启用定时器产生周期性的中断。 If a timer is set to be periodic, its period is added to the match register each time a match occurs, thus computing the next time for this timer to generate an interrupt..如果定时器被设置为周期，其周期被添加到匹配寄存器，每次比赛时，从而计算该计时器下一次产生一个中断.. An up-counter is usually 64 bits wide but 32-bit implementations are permitted by the specification and 64-bit up-counters can also be driven in 32-bit mode.向上的计数器通常是64位元宽，但32位的实现是由规范和64位向上计数器允许也可以在32位模式驱动。 Up-counters run at a minimum of 10 MHz.最新的计数器运行在10 MHz的最低水平。 which is much faster than the older这是速度远远超过了旧 RTC实时时钟 (Real Time Clock) and can thus produce periodic interrupts at a much higher resolution. （实时时钟），所以可以产生高得多的分辨率在定期中断。 The registers associated with these timers are mapped to memory space.与这些定时器相关的寄存器映射到内存空间。
The BIOS uses BIOS使用 ACPI支持ACPI ( Advanced Configuration and Power Interface) functionality to inform the operating system of the location of the HPET memory-mapped register space. （高级配置和电源接口）功能，以告知该HPET内存映射寄存器空间位置的操作系统。 Here is an example of a disassembled ACPI HPET table from an Intel DX48BT2 (AKA BoneTrail) motherboard.这里是一个拆散的ACPI HPET表从一个Intel DX48BT2（又名BoneTrail）主板的例子。
$ cat /sys/firmware/acpi/tables/HPET > /var/tmp/hpet.out $ iasl -d /var/tmp/hpet.out $ cat /var/tmp/hpet.dsl /* * Intel ACPI Component Architecture * AML Disassembler version 20090123 * * Disassembly of /var/tmp/hpet.out, Sun Jul 5 19:34:47 2009 * * ACPI Data Table [HPET] * * Format: [HexOffset DecimalOffset ByteLength] FieldName : FieldValue */ [000h 000 4] Signature : "HPET" /* High Precision Event Timer table */ [004h 004 4] Table Length : 00000038 [008h 008 1] Revision : 01 [009h 009 1] Checksum : CE [00Ah 010 6] Oem ID : "INTEL " [010h 016 8] Oem Table ID : "DX48BT2 " [018h 024 4] Oem Revision : 0000076E [01Ch 028 4] Asl Compiler ID : "MSFT" [020h 032 4] Asl Compiler Revision : 01000013 [024h 036 4] Hardware Block ID : 8086A301 [028h 040 12] Timer Block Register :[028h 040 1] Space ID : 00 (SystemMemory) [029h 041 1] Bit Width : 00 [02Ah 042 1] Bit Offset : 00 [02Bh 043 1] Access Width : 00 [02Ch 044 8] Address : 00000000FED00000 [034h 052 1] Sequence Number : 00 [035h 053 2] Minimum Clock Ticks : 0001 [037h 055 1] Flags (decoded below) : 00 Page Protect : 0 4K Page Protect : 0 64K Page Protect : 0 Raw Table Data 0000: 48 50 45 54 38 00 00 00 01 CE 49 4E 54 45 4C 20 HPET8.....INTEL 0010: 44 58 34 38 42 54 32 20 6E 07 00 00 4D 53 46 54 DX48BT2 n...MSFT 0020: 13 00 00 01 01 A3 86 80 00 00 00 00 00 00 D0 FE ................ 0030: 00 00 00 00 00 01 00 00 ........ $
See page 30 of the HPET v1.0a specification for a detailed breakdown of the individual bits in the Event Time Block (called Hardware Block by the AML disassember).查看在活动时间块（称为反洗钱disassember由硬件模块）的各个位详细分类页HPET v1.0a规范30。 Note that only one Event Timer Block need be described in the HPET table in order to bootstrap an operating system.请注意，只有1座事件定时器需要在HPET表所述，以引导操作系统。 This is the case here.这是这里的情况。 For non-legacy platforms, the Event Timer Block described in the HPET is the one that provides functionality to replace the 8254/RTC Periodic Interrupt Logic.对于非传统平台，事件定时器座在HPET描述是一个提供的功能，以取代8254/RTC周期中断逻辑。
Other Event Time Blocks are described in the ACPI namespace.其他活动的时间段中描述的ACPI命名空间。 Here is the relevant section from the disassembled ACPI DSDT table.下面是从拆解的ACPI DSDT表的有关部分。
Device (HPET)
{
Name (_HID, EisaId ("PNP0103"))
Name (_CRS, ResourceTemplate ()
{
Memory32Fixed (ReadOnly,
0xFED00000, // Address Base
0x00004000, // Address Length
)
})
Method (_STA, 0, NotSerialized)
{
If (HPEE)
{
Return (0x0F)
}
Else
{
Return (Zero)
}
}
}
Note the assigned PNPID ( PNP0103 ) for the HPET.请注意分配）的HPET PNPID（PNP0103。 Because no _UID is specified it means that there are no other HPET timer blocks.因为没有_UID指定这意味着没有其他HPET计时器块。
Here is a list of the HPET-related messages outputted when this particular motherboard is booted up under Fedora 11.这里是HPET相关输出信息时，这个名单是主板的Fedora 11下启动了。
$ dmesg | grep -i HPET ACPI: HPET CFBF2000, 0038 (r1 INTEL DX48BT2 76E MSFT 1000013) ACPI: HPET id: 0x8086a301 base: 0xfed00000 hpet clockevent registered HPET: 4 timers in total, 0 timers will be used for per-cpu timer hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0, 0 hpet0: 4 comparators, 64-bit 14.318180 MHz counter rtc0: alarms up to one month, 114 bytes nvram, hpet irqs $
The first line is outputted when the ACPI HPET table is read.第一行是输出时的ACPI HPET表是只读。 The second line is outputted when the ACPI HPET table is mapped into memory by …/arch/x86/kernel/acpi/boot.c .第二行是输出时的ACPI HPET表映射到内存... / arch/x86/kernel/acpi/boot.c。 The next line is outputted when the HPET legacy interrupts are started and HPET is registered as the global clock.下一行是输出时遗留下来的HPET中断开始，HPET是全球时钟登记。 The following line is outputted when the kernel checks to ensure that at least one timer is reserved for userspace ( /dev/hpet .) The next two lines of output comes from the HPET device driver ( …/drivers/char/hpet.c .) It shows that 2 timers have allocated interrupts and two do not..下面的行输出是当内核检查，以确保至少有一个计时器，是留给用户空间（/开发/ hpet。）接下来的两行输出来自HPET设备驱动程序（... /司机/炭/ hpet.c。 ）这表明，已拨出2定时器中断和两个不..
Here is the relevant part of the output from /proc/time_list as it relates to HPET:以下是有关部分涉及到HPET的输出从/ proc / time_list因为它：
Tick Device: mode: 1 Broadcast device Clock Event Device: hpet max_delta_ns: 149983005959 min_delta_ns: 5000 mult: 61496114 shift: 32 mode: 3 next_event: 9223372036854775807 nsecs set_next_event: hpet_legacy_next_event set_mode: hpet_legacy_set_mode event_handler: tick_handle_oneshot_broadcast tick_broadcast_mask: 00000000 tick_broadcast_oneshot_mask: 00000000
Here is the output from /proc/sys/dev/hpet and /proc/driver/rtc :下面是输出的RTC从/ proc / sys目录下的/ dev / hpet和/ proc /司机/：
$ cat /proc/sys/dev/hpet/max-user-freq 64 $ cat /proc/driver/rtc rtc_time : 06:34:31 rtc_date : 2009-07-06 alrm_time : **:24:40 alrm_date : ****-**-** alarm_IRQ : no alrm_pending : no 24hr : yes periodic_IRQ : no update_IRQ : no HPET_emulated : yes DST_enable : no periodic_freq : 1024 batt_status : okay
The HPET driver ( /dev/hpet ) has a similar API to the Real Time Clock driver.该HPET驱动程序（/开发/ hpet）也有类似的API来实时时钟驱动程序。 It is a character device which can support any number of HPET devices.这是一个字符设备，可以支持任何HPET设备的数量。 The kernel API has three interfaces exported from the driver:该内核API已经从司机出口三个接口：
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 userspace interface to HPET is defined in the header /usr/include/linux/hpet.h .用户空间接口HPET是定义在头/ usr / include中/ Linux的/ hpet.h。 The current set of supported operations is:目前所支持的操作集是：
#define HPET_IE_ON _IO('h', 0x01) /* interrupt on */
#define HPET_IE_OFF _IO('h', 0x02) /* interrupt off */
#define HPET_INFO _IOR('h', 0x03, struct hpet_info) /* get information */
#define HPET_EPI _IO('h', 0x04) /* enable periodic */
#define HPET_DPI _IO('h', 0x05) /* disable periodic */
#define HPET_IRQFREQ _IOW('h', 0x6, unsigned long) /* set frequency */
The following example shows how to use the published interface to access a HPET and call a simple periodic signal handler hpet_alarm between 2 and 99 times a second.下面的示例演示如何使用已发布的接口访问HPET并调用一个简单的周期信号处理器hpet_alarm 2至99次。
#include <stdio.h>
#include <stdlib.h;>
#include <fcntl.h>
#include <time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/time.h>
#include <linux/hpet.h>
#include <stdint.h>
#include <sys/ioctl.h>
#include <signal.h>
static uint16_t hpet_sigio_count;
static uint64_t secs;
static void
hpet_alarm(int val)
{
struct timespec t;
clock_gettime(CLOCK_REALTIME, &t);
if (!secs) secs = t.tv_sec;
fprintf(stderr, "hpet_alarm called. iteration: %2d secs: %ld nsecs: %ld \n",
hpet_sigio_count, (t.tv_sec - secs) , t.tv_sec * 100000 + t.tv_nsec );
hpet_sigio_count++;
}
int
main(int argc, const char **argv)
{
struct sigaction old, new;
struct hpet_info info;
int frequency;
int iterations;
int retval = 0;
int fd;
int r, i, value;
if (argc != 3) {
fprintf(stderr, "Usage: %s frequency(1-64) iterations(10-99)\n", argv[0]);
return -1;
}
frequency = atoi(argv[1]);
iterations = atoi(argv[2]);
if (frequency > 64 || frequency < 1 ) {
fprintf(stderr, "ERROR: Invalid value for frequency\n");
return -1;
}
if (iterations < 10 || iterations > 99 ) {
fprintf(stderr, "ERROR: Invalid value for iterations\n");
return -1;
}
hpet_sigio_count = 0;
sigemptyset(&new.sa_mask);
new.sa_flags = 0;
new.sa_handler = hpet_alarm;
sigaction(SIGIO, NULL, &old);
sigaction(SIGIO, &new, NULL);
fd = open("/dev/hpet", O_RDONLY);
if (fd < 0) {
fprintf(stderr, "ERROR: Failed to open /dev/hpet\n");
return -1;
}
if ((fcntl(fd, F_SETOWN, getpid()) == 1) ||
((value = fcntl(fd, F_GETFL)) == 1) ||
(fcntl(fd, F_SETFL, value | O_ASYNC) == 1)) {
fprintf(stderr, "ERROR: fcntl failed\n");
retval = 1;
goto fail;
}
if (ioctl(fd, HPET_IRQFREQ, frequency) < 0) {
fprintf(stderr, "ERROR: Could not set /dev/hpet to have a %2dHz timer\n", frequency);
retval = 2;
goto fail;
}
if (ioctl(fd, HPET_INFO, &info) < 0) {
fprintf(stderr, "ERROR: failed to get info\n");
retval = 3;
goto fail;
}
fprintf(stdout, "\nhi_ireqfreq: 0x%lx hi_flags: %0x%lx hi_hpet: 0x%x hi_timer: 0x%x\n\n",
info.hi_ireqfreq, info.hi_flags, info.hi_hpet, info.hi_timer);
r = ioctl(fd, HPET_EPI, 0);
if (info.hi_flags && (r < 0)) {
fprintf(stderr, "ERROR: HPET_EPI failed\n");
retval = 4;
goto fail;
}
if (ioctl(fd, HPET_IE_ON, 0) < 0) {
fprintf(stderr, "ERROR: HPET_IE_ON failed\n");
retval = 5;
goto fail;
}
/* wait for specified number of signal interrupts */
for (i = 0; i < iterations; i++) {
(void) pause();
}
if (ioctl(fd, HPET_IE_OFF, 0) < 0) {
fprintf(stderr, "ERROR: HPET_IE_OFF failed\n");
retval = 6;
}
fail:
sigaction(SIGIO, &old, NULL);
if (fd > 0)
close(fd);
return retval;
}
Here is the output from this example when it is invoked with a frequency of 32 and an iteration count of 64.下面是从这个时候它是调用了32个频率和迭代次数为64示例输出。
$ sudo ./hpet_example 32 64 hi_ireqfreq: 0x20 hi_flags: 00 hi_hpet: 0x2 hi_timer: 0x4a1cb9c8 hpet_alarm called. iteration: 0 secs: 0 nsecs: 124683205055050 hpet_alarm called. iteration: 1 secs: 0 nsecs: 124683236313149 hpet_alarm called. iteration: 2 secs: 0 nsecs: 124683267566342 hpet_alarm called. iteration: 3 secs: 0 nsecs: 124683298821905 hpet_alarm called. iteration: 4 secs: 0 nsecs: 124683330077493 hpet_alarm called. iteration: 5 secs: 0 nsecs: 124683361341893 hpet_alarm called. iteration: 6 secs: 0 nsecs: 124683392590764 hpet_alarm called. iteration: 7 secs: 0 nsecs: 124683423849157 hpet_alarm called. iteration: 8 secs: 0 nsecs: 124683455101917 hpet_alarm called. iteration: 9 secs: 0 nsecs: 124683486357683 hpet_alarm called. iteration: 10 secs: 0 nsecs: 124683517617931 hpet_alarm called. iteration: 11 secs: 0 nsecs: 124683548872198 hpet_alarm called. iteration: 12 secs: 1 nsecs: 124682580229541 hpet_alarm called. iteration: 13 secs: 1 nsecs: 124682611481235 hpet_alarm called. iteration: 14 secs: 1 nsecs: 124682642740016 hpet_alarm called. iteration: 15 secs: 1 nsecs: 124682673992697 hpet_alarm called. iteration: 16 secs: 1 nsecs: 124682705247479 hpet_alarm called. iteration: 17 secs: 1 nsecs: 124682736504664 hpet_alarm called. iteration: 18 secs: 1 nsecs: 124682767758840 hpet_alarm called. iteration: 19 secs: 1 nsecs: 124682799014280 hpet_alarm called. iteration: 20 secs: 1 nsecs: 124682830270129 hpet_alarm called. iteration: 21 secs: 1 nsecs: 124682861530334 hpet_alarm called. iteration: 22 secs: 1 nsecs: 124682892784577 hpet_alarm called. iteration: 23 secs: 1 nsecs: 124682924038220 hpet_alarm called. iteration: 24 secs: 1 nsecs: 124682955294110 hpet_alarm called. iteration: 25 secs: 1 nsecs: 124682986550572 hpet_alarm called. iteration: 26 secs: 1 nsecs: 124683017805756 hpet_alarm called. iteration: 27 secs: 1 nsecs: 124683049061117 hpet_alarm called. iteration: 28 secs: 1 nsecs: 124683080318331 hpet_alarm called. iteration: 29 secs: 1 nsecs: 124683111576954 hpet_alarm called. iteration: 30 secs: 1 nsecs: 124683142828988 hpet_alarm called. iteration: 31 secs: 1 nsecs: 124683174083954 hpet_alarm called. iteration: 32 secs: 1 nsecs: 124683205337967 hpet_alarm called. iteration: 33 secs: 1 nsecs: 124683236593144 hpet_alarm called. iteration: 34 secs: 1 nsecs: 124683267851530 hpet_alarm called. iteration: 35 secs: 1 nsecs: 124683299104054 hpet_alarm called. iteration: 36 secs: 1 nsecs: 124683330358748 hpet_alarm called. iteration: 37 secs: 1 nsecs: 124683361617445 hpet_alarm called. iteration: 38 secs: 1 nsecs: 124683392870249 hpet_alarm called. iteration: 39 secs: 1 nsecs: 124683424124489 hpet_alarm called. iteration: 40 secs: 1 nsecs: 124683455379717 hpet_alarm called. iteration: 41 secs: 1 nsecs: 124683486634424 hpet_alarm called. iteration: 42 secs: 1 nsecs: 124683517889149 hpet_alarm called. iteration: 43 secs: 1 nsecs: 124683549144315 hpet_alarm called. iteration: 44 secs: 2 nsecs: 124682580500695 hpet_alarm called. iteration: 45 secs: 2 nsecs: 124682611761325 hpet_alarm called. iteration: 46 secs: 2 nsecs: 124682643011863 hpet_alarm called. iteration: 47 secs: 2 nsecs: 124682674265864 hpet_alarm called. iteration: 48 secs: 2 nsecs: 124682705521034 hpet_alarm called. iteration: 49 secs: 2 nsecs: 124682736776049 hpet_alarm called. iteration: 50 secs: 2 nsecs: 124682768030654 hpet_alarm called. iteration: 51 secs: 2 nsecs: 124682799285398 hpet_alarm called. iteration: 52 secs: 2 nsecs: 124682830544701 hpet_alarm called. iteration: 53 secs: 2 nsecs: 124682861797319 hpet_alarm called. iteration: 54 secs: 2 nsecs: 124682893051578 hpet_alarm called. iteration: 55 secs: 2 nsecs: 124682924306748 hpet_alarm called. iteration: 56 secs: 2 nsecs: 124682955562132 hpet_alarm called. iteration: 57 secs: 2 nsecs: 124682986823545 hpet_alarm called. iteration: 58 secs: 2 nsecs: 124683018073636 hpet_alarm called. iteration: 59 secs: 2 nsecs: 124683049327560 hpet_alarm called. iteration: 60 secs: 2 nsecs: 124683080586707 hpet_alarm called. iteration: 61 secs: 2 nsecs: 124683111841132 hpet_alarm called. iteration: 62 secs: 2 nsecs: 124683143095147 hpet_alarm called. iteration: 63 secs: 2 nsecs: 124683174349985 hpet_alarm called. iteration: 64 secs: 2 nsecs: 124683205607103 $
Well, I think that I have provided you with enough information so that you should now be able to go away and experiment with the HPET interface yourself.嗯，我认为我已提供了足够的信息，以便您现在应该可以回去自己的HPET接口实验。
By the way, not all VMware products support HPET.顺便说一下，不是所有的VMware产品支持HPET。 Currently ESX does not provide a virtual HPET to guest operating systems and in some cases it may be necessary to disable HPET altogether because of timer drift in virtual machines.目前的ESX不提供一个虚拟HPET为客人作业系统并在一些情况下，可能需要禁用HPET计时器漂移完全是因为在虚拟机。 See 见 VMware TimeKeeping VMware的时钟 for more information.获取更多信息。
PS I tested the the above example on an Intel DX48BT2 motherboard running a 2.6.29.5-191 kernel. PS我测试的Intel DX48BT2运行2.6.29.5-191内核主板上面的例子。
