1/* Ported over from i386 by AK, original copyright was:
2 *
3 * (C) Dominik Brodowski <linux@brodo.de> 2003
4 *
5 * Driver to use the Power Management Timer (PMTMR) available in some
6 * southbridges as primary timing source for the Linux kernel.
7 *
8 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
9 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
10 *
11 * This file is licensed under the GPL v2.
12 *
13 * Dropped all the hardware bug workarounds for now. Hopefully they
14 * are not needed on 64bit chipsets.
15 */
16
17#include <linux/jiffies.h>
18#include <linux/kernel.h>
19#include <linux/time.h>
20#include <linux/init.h>
21#include <linux/cpumask.h>
22#include <asm/io.h>
23#include <asm/proto.h>
24#include <asm/msr.h>
25#include <asm/vsyscall.h>
26
27#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
28
29static inline u32 cyc2us(u32 cycles)
30{
31	/* The Power Management Timer ticks at 3.579545 ticks per microsecond.
32	 * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
33	 *
34	 * Even with HZ = 100, delta is at maximum 35796 ticks, so it can
35	 * easily be multiplied with 286 (=0x11E) without having to fear
36	 * u32 overflows.
37	 */
38	cycles *= 286;
39	return (cycles >> 10);
40}
41
42static unsigned pmtimer_wait_tick(void)
43{
44	u32 a, b;
45	for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK;
46	     a == b;
47	     b = inl(pmtmr_ioport) & ACPI_PM_MASK)
48		cpu_relax();
49	return b;
50}
51
52/* note: wait time is rounded up to one tick */
53void pmtimer_wait(unsigned us)
54{
55	u32 a, b;
56	a = pmtimer_wait_tick();
57	do {
58		b = inl(pmtmr_ioport);
59		cpu_relax();
60	} while (cyc2us(b - a) < us);
61}
62
63static int __init nopmtimer_setup(char *s)
64{
65	pmtmr_ioport = 0;
66	return 1;
67}
68
69__setup("nopmtimer", nopmtimer_setup);
70