1 /* Ported over from i386 by AK, original copyright was:
3 * (C) Dominik Brodowski <linux@brodo.de> 2003
5 * Driver to use the Power Management Timer (PMTMR) available in some
6 * southbridges as primary timing source for the Linux kernel.
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.
11 * This file is licensed under the GPL v2.
13 * Dropped all the hardware bug workarounds for now. Hopefully they
14 * are not needed on 64bit chipsets.
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>
23 #include <asm/proto.h>
25 #include <asm/vsyscall.h>
27 /* The I/O port the PMTMR resides at.
28 * The location is detected during setup_arch(),
29 * in arch/i386/kernel/acpi/boot.c */
32 /* value of the Power timer at last timer interrupt */
33 static u32 offset_delay;
34 static u32 last_pmtmr_tick;
36 #define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
38 static inline u32 cyc2us(u32 cycles)
40 /* The Power Management Timer ticks at 3.579545 ticks per microsecond.
41 * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
43 * Even with HZ = 100, delta is at maximum 35796 ticks, so it can
44 * easily be multiplied with 286 (=0x11E) without having to fear
48 return (cycles >> 10);
51 int pmtimer_mark_offset(void)
53 static int first_run = 1;
57 u32 tick = inl(pmtmr_ioport);
60 delta = cyc2us((tick - last_pmtmr_tick) & ACPI_PM_MASK);
62 last_pmtmr_tick = tick;
63 monotonic_base += delta * NSEC_PER_USEC;
65 delta += offset_delay;
67 lost = delta / (USEC_PER_SEC / HZ);
68 offset_delay = delta % (USEC_PER_SEC / HZ);
71 vxtime.last_tsc = tsc - offset_delay * (u64)cpu_khz / 1000;
73 /* don't calculate delay for first run,
74 or if we've got less then a tick */
75 if (first_run || (lost < 1)) {
83 static unsigned pmtimer_wait_tick(void)
86 for (a = b = inl(pmtmr_ioport) & ACPI_PM_MASK;
88 b = inl(pmtmr_ioport) & ACPI_PM_MASK)
93 /* note: wait time is rounded up to one tick */
94 void pmtimer_wait(unsigned us)
97 a = pmtimer_wait_tick();
99 b = inl(pmtmr_ioport);
101 } while (cyc2us(b - a) < us);
104 void pmtimer_resume(void)
106 last_pmtmr_tick = inl(pmtmr_ioport);
109 unsigned int do_gettimeoffset_pm(void)
111 u32 now, offset, delta = 0;
113 offset = last_pmtmr_tick;
114 now = inl(pmtmr_ioport);
115 delta = (now - offset) & ACPI_PM_MASK;
117 return offset_delay + cyc2us(delta);
121 static int __init nopmtimer_setup(char *s)
127 __setup("nopmtimer", nopmtimer_setup);