| Andi Kleen | 312df5f | 2005-05-16 21:53:28 -0700 | [diff] [blame] | 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 | /* The I/O port the PMTMR resides at. |
| 28 | * The location is detected during setup_arch(), |
| 29 | * in arch/i386/kernel/acpi/boot.c */ |
| 30 | u32 pmtmr_ioport; |
| 31 | |
| 32 | /* value of the Power timer at last timer interrupt */ |
| 33 | static u32 offset_delay; |
| 34 | static u32 last_pmtmr_tick; |
| 35 | |
| 36 | #define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */ |
| 37 | |
| 38 | static inline u32 cyc2us(u32 cycles) |
| 39 | { |
| 40 | /* The Power Management Timer ticks at 3.579545 ticks per microsecond. |
| 41 | * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%] |
| 42 | * |
| 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 |
| 45 | * u32 overflows. |
| 46 | */ |
| 47 | cycles *= 286; |
| 48 | return (cycles >> 10); |
| 49 | } |
| 50 | |
| 51 | int pmtimer_mark_offset(void) |
| 52 | { |
| 53 | static int first_run = 1; |
| 54 | unsigned long tsc; |
| 55 | u32 lost; |
| 56 | |
| 57 | u32 tick = inl(pmtmr_ioport); |
| 58 | u32 delta; |
| 59 | |
| 60 | delta = cyc2us((tick - last_pmtmr_tick) & ACPI_PM_MASK); |
| 61 | |
| 62 | last_pmtmr_tick = tick; |
| 63 | monotonic_base += delta * NSEC_PER_USEC; |
| 64 | |
| 65 | delta += offset_delay; |
| 66 | |
| 67 | lost = delta / (USEC_PER_SEC / HZ); |
| 68 | offset_delay = delta % (USEC_PER_SEC / HZ); |
| 69 | |
| 70 | rdtscll(tsc); |
| 71 | vxtime.last_tsc = tsc - offset_delay * cpu_khz; |
| 72 | |
| 73 | /* don't calculate delay for first run, |
| 74 | or if we've got less then a tick */ |
| 75 | if (first_run || (lost < 1)) { |
| 76 | first_run = 0; |
| 77 | offset_delay = 0; |
| 78 | } |
| 79 | |
| 80 | return lost - 1; |
| 81 | } |
| 82 | |
| 83 | unsigned int do_gettimeoffset_pm(void) |
| 84 | { |
| 85 | u32 now, offset, delta = 0; |
| 86 | |
| 87 | offset = last_pmtmr_tick; |
| 88 | now = inl(pmtmr_ioport); |
| 89 | delta = (now - offset) & ACPI_PM_MASK; |
| 90 | |
| 91 | return offset_delay + cyc2us(delta); |
| 92 | } |
| 93 | |
| 94 | |
| 95 | static int __init nopmtimer_setup(char *s) |
| 96 | { |
| 97 | pmtmr_ioport = 0; |
| 98 | return 0; |
| 99 | } |
| 100 | |
| 101 | __setup("nopmtimer", nopmtimer_setup); |