[mirror_ubuntu-artful-kernel.git] / arch / i386 / kernel / hpet.c

#include <linux/clocksource.h>
#include <linux/errno.h>
#include <linux/hpet.h>
#include <linux/init.h>

#include <asm/hpet.h>
#include <asm/io.h>

#define HPET_MASK	0xFFFFFFFF
#define HPET_SHIFT	22

/* FSEC = 10^-15 NSEC = 10^-9 */
#define FSEC_PER_NSEC	1000000

static void *hpet_ptr;

static cycle_t read_hpet(void)
{
	return (cycle_t)readl(hpet_ptr);
}

static struct clocksource clocksource_hpet = {
	.name		= "hpet",
	.rating		= 250,
	.read		= read_hpet,
	.mask		= (cycle_t)HPET_MASK,
	.mult		= 0, /* set below */
	.shift		= HPET_SHIFT,
	.is_continuous	= 1,
};

static int __init init_hpet_clocksource(void)
{
	unsigned long hpet_period;
	void __iomem* hpet_base;
	u64 tmp;

	if (!hpet_address)
		return -ENODEV;

	/* calculate the hpet address: */
	hpet_base =
		(void __iomem*)ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
	hpet_ptr = hpet_base + HPET_COUNTER;

	/* calculate the frequency: */
	hpet_period = readl(hpet_base + HPET_PERIOD);

	/*
	 * hpet period is in femto seconds per cycle
	 * so we need to convert this to ns/cyc units
	 * aproximated by mult/2^shift
	 *
	 *  fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
	 *  fsec/cyc * 1ns/1000000fsec * 2^shift = mult
	 *  fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
	 *  (fsec/cyc << shift)/1000000 = mult
	 *  (hpet_period << shift)/FSEC_PER_NSEC = mult
	 */
	tmp = (u64)hpet_period << HPET_SHIFT;
	do_div(tmp, FSEC_PER_NSEC);
	clocksource_hpet.mult = (u32)tmp;

	return clocksource_register(&clocksource_hpet);
}

module_init(init_hpet_clocksource);
Commit	Line	Data
5d0cf410 JS	1	#include <linux/clocksource.h>
	2	#include <linux/errno.h>
	3	#include <linux/hpet.h>
	4	#include <linux/init.h>
	5
	6	#include <asm/hpet.h>
	7	#include <asm/io.h>
	8
	9	#define HPET_MASK 0xFFFFFFFF
	10	#define HPET_SHIFT 22
	11
	12	/* FSEC = 10^-15 NSEC = 10^-9 */
	13	#define FSEC_PER_NSEC 1000000
	14
	15	static void *hpet_ptr;
	16
	17	static cycle_t read_hpet(void)
	18	{
	19	return (cycle_t)readl(hpet_ptr);
	20	}
	21
	22	static struct clocksource clocksource_hpet = {
	23	.name = "hpet",
	24	.rating = 250,
	25	.read = read_hpet,
	26	.mask = (cycle_t)HPET_MASK,
	27	.mult = 0, /* set below */
	28	.shift = HPET_SHIFT,
	29	.is_continuous = 1,
	30	};
	31
	32	static int __init init_hpet_clocksource(void)
	33	{
	34	unsigned long hpet_period;
	35	void __iomem* hpet_base;
	36	u64 tmp;
	37
	38	if (!hpet_address)
	39	return -ENODEV;
	40
	41	/* calculate the hpet address: */
	42	hpet_base =
	43	(void __iomem*)ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
	44	hpet_ptr = hpet_base + HPET_COUNTER;
	45
	46	/* calculate the frequency: */
	47	hpet_period = readl(hpet_base + HPET_PERIOD);
	48
	49	/*
	50	* hpet period is in femto seconds per cycle
	51	* so we need to convert this to ns/cyc units
	52	* aproximated by mult/2^shift
	53	*
	54	* fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
	55	* fsec/cyc * 1ns/1000000fsec * 2^shift = mult
	56	* fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
	57	* (fsec/cyc << shift)/1000000 = mult
	58	* (hpet_period << shift)/FSEC_PER_NSEC = mult
	59	*/
	60	tmp = (u64)hpet_period << HPET_SHIFT;
	61	do_div(tmp, FSEC_PER_NSEC);
	62	clocksource_hpet.mult = (u32)tmp;
	63
a2752549	64	return clocksource_register(&clocksource_hpet);
5d0cf410 JS	65	}
	66
	67	module_init(init_hpet_clocksource);