/*
* (C) Dominik Brodowski <linux@brodo.de> 2003
*
* Driver to use the Power Management Timer (PMTMR) available in some
* southbridges as primary timing source for the Linux kernel.
*
* Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
* timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
*
* This file is licensed under the GPL v2.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/init.h>
#include <asm/types.h>
#include <asm/timer.h>
#include <asm/smp.h>
#include <asm/io.h>
#include <asm/arch_hooks.h>
#include <linux/timex.h>
#include "mach_timer.h"
/* Number of PMTMR ticks expected during calibration run */
#define PMTMR_TICKS_PER_SEC 3579545
#define PMTMR_EXPECTED_RATE \
((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
/* The I/O port the PMTMR resides at.
* The location is detected during setup_arch(),
* in arch/i386/acpi/boot.c */
u32 pmtmr_ioport = 0;
/* value of the Power timer at last timer interrupt */
static u32 offset_tick;
static u32 offset_delay;
static unsigned long long monotonic_base;
static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
/*helper function to safely read acpi pm timesource*/
static inline u32 read_pmtmr(void)
{
u32 v1=0,v2=0,v3=0;
/* It has been reported that because of various broken
* chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM time
* source is not latched, so you must read it multiple
* times to insure a safe value is read.
*/
do {
v1 = inl(pmtmr_ioport);
v2 = inl(pmtmr_ioport);
v3 = inl(pmtmr_ioport);
} while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
|| (v3 > v1 && v3 < v2));
/* mask the output to 24 bits */
return v2 & ACPI_PM_MASK;
}
/*
* Some boards have the PMTMR running way too fast. We check
* the PMTMR rate against PIT channel 2 to catch these cases.
*/
static int verify_pmtmr_rate(void)
{
u32 value1, value2;
unsigned long count, delta;
mach_prepare_counter();
value1 = read_pmtmr();
mach_countup(&count);
value2 = read_pmtmr();
delta = (value2 - value1) & ACPI_PM_MASK;
/* Check that the PMTMR delta is within 5% of what we expect */
if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% of normal - aborting.\n", 100UL * delta / PMTMR_EXPECTED_RATE);
return -1;
}
return 0;
}
static int init_pmtmr(char* override)
{
u32 value1, value2;
unsigned int i;
if (override[0] && strncmp(override,"pmtmr",5))
return -ENODEV;
if (!pmtmr_ioport)
return -ENODEV;
/* we use the TSC for delay_pmtmr, so make sure it exists */
if (!cpu_has_tsc)
return -ENODEV;
/* "verify" this timing source */
value1 = read_pmtmr();
for (i = 0; i < 10000; i++) {
value2 = read_pmtmr();
if (value2 == value1)
continue;
if (value2 > value1)
goto pm_good;
if ((value2 < value1) && ((value2) < 0xFFF))
goto pm_good;
printk(KERN_INFO "PM-Timer had inconsistent results: 0x%#x, 0x%#x - aborting.\n", value1, value2);
return -EINVAL;
}
printk(KERN_INFO "PM-Timer had no reasonable result: 0x%#x - aborting.\n", value1);
return -ENODEV;
pm_good:
if (verify_pmtmr_rate() != 0)
return -ENODEV;
init_cpu_khz();
return 0;
}
static inline u32 cyc2us(u32 cycles)
{
/* The Power Management Timer ticks at 3.579545 ticks per microsecond.
* 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
*
* Even with HZ = 100, delta is at maximum 35796 ticks, so it can
* easily be multiplied with 286 (=0x11E) without having to fear
* u32 overflows.
*/
cycles *= 286;
return (cycles >> 10);
}
/*
* this gets called during each timer interrupt
* - Called while holding the writer xtime_lock
*/
static void mark_offset_pmtmr(void)
{
u32 lost, delta, last_offset;
static int first_run = 1;
last_offset = offset_tick;
write_seqlock(&monotonic_lock);
offset_tick = read_pmtmr();
/* calculate tick interval */
delta = (offset_tick - last_offset) & ACPI_PM_MASK;
/* convert to usecs */
delta = cyc2us(delta);
/* update the monotonic base value */
monotonic_base += delta * NSEC_PER_USEC;
write_sequnlock(&monotonic_lock);
/* convert to ticks */
delta += offset_delay;
lost = delta / (USEC_PER_SEC / HZ);
offset_delay = delta % (USEC_PER_SEC / HZ);
/* compensate for lost ticks */
if (lost >= 2)
jiffies_64 += lost - 1;
/* don't calculate delay for first run,
or if we've got less then a tick */
if (first_run || (lost < 1)) {
first_run = 0;
offset_delay = 0;
}
}
static int pmtmr_resume(void)
{
write_seqlock(&monotonic_lock);
/* Assume this is the last mark offset time */
offset_tick = read_pmtmr();
write_sequnlock(&monotonic_lock);
return 0;
}
static unsigned long long monotonic_clock_pmtmr(void)
{
u32 last_offset, this_offset;
unsigned long long base, ret;
unsigned seq;
/* atomically read monotonic base & last_offset */
do {
seq = read_seqbegin(&monotonic_lock);
last_offset = offset_tick;
base = monotonic_base;
} while (read_seqretry(&monotonic_lock, seq));
/* Read the pmtmr */
this_offset = read_pmtmr();
/* convert to nanoseconds */
ret = (this_offset - last_offset) & ACPI_PM_MASK;
ret = base + (cyc2us(ret) * NSEC_PER_USEC);
return ret;
}
static void delay_pmtmr(unsigned long loops)
{
unsigned long bclock, now;
rdtscl(bclock);
do
{
rep_nop();
rdtscl(now);
} while ((now-bclock) < loops);
}
/*
* get the offset (in microseconds) from the last call to mark_offset()
* - Called holding a reader xtime_lock
*/
static unsigned long get_offset_pmtmr(void)
{
u32 now, offset, delta = 0;
offset = offset_tick;
now = read_pmtmr();
delta = (now - offset)&ACPI_PM_MASK;
return (unsigned long) offset_delay + cyc2us(delta);
}
/* acpi timer_opts struct */
static struct timer_opts timer_pmtmr = {
.name = "pmtmr",
.mark_offset = mark_offset_pmtmr,
.get_offset = get_offset_pmtmr,
.monotonic_clock = monotonic_clock_pmtmr,
.delay = delay_pmtmr,
.read_timer = read_timer_tsc,
.resume = pmtmr_resume,
};
struct init_timer_opts __initdata timer_pmtmr_init = {
.init = init_pmtmr,
.opts = &timer_pmtmr,
};
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
MODULE_DESCRIPTION("Power Management Timer (PMTMR) as primary timing source for x86");
