/* * (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");