1/*
2 * linux/drivers/clocksource/acpi_pm.c
3 *
4 * This file contains the ACPI PM based clocksource.
5 *
6 * This code was largely moved from the i386 timer_pm.c file
7 * which was (C) Dominik Brodowski <linux@brodo.de> 2003
8 * and contained the following comments:
9 *
10 * Driver to use the Power Management Timer (PMTMR) available in some
11 * southbridges as primary timing source for the Linux kernel.
12 *
13 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
14 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
15 *
16 * This file is licensed under the GPL v2.
17 */
18
19#include <linux/acpi_pmtmr.h>
20#include <linux/clocksource.h>
21#include <linux/timex.h>
22#include <linux/errno.h>
23#include <linux/init.h>
24#include <linux/pci.h>
25#include <linux/delay.h>
26#include <asm/io.h>
27
28/*
29 * The I/O port the PMTMR resides at.
30 * The location is detected during setup_arch(),
31 * in arch/i386/kernel/acpi/boot.c
32 */
33u32 pmtmr_ioport __read_mostly;
34
35static inline u32 read_pmtmr(void)
36{
37 /* mask the output to 24 bits */
38 return inl(pmtmr_ioport) & ACPI_PM_MASK;
39}
40
41u32 acpi_pm_read_verified(void)
42{
43 u32 v1 = 0, v2 = 0, v3 = 0;
44
45 /*
46 * It has been reported that because of various broken
47 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock
48 * source is not latched, you must read it multiple
49 * times to ensure a safe value is read:
50 */
51 do {
52 v1 = read_pmtmr();
53 v2 = read_pmtmr();
54 v3 = read_pmtmr();
55 } while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
56 || (v3 > v1 && v3 < v2)));
57
58 return v2;
59}
60
61static u64 acpi_pm_read(struct clocksource *cs)
62{
63 return (u64)read_pmtmr();
64}
65
66static struct clocksource clocksource_acpi_pm = {
67 .name = "acpi_pm",
68 .rating = 200,
69 .read = acpi_pm_read,
70 .mask = (u64)ACPI_PM_MASK,
71 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
72};
73
74
75#ifdef CONFIG_PCI
76static int acpi_pm_good;
77static int __init acpi_pm_good_setup(char *__str)
78{
79 acpi_pm_good = 1;
80 return 1;
81}
82__setup("acpi_pm_good", acpi_pm_good_setup);
83
84static u64 acpi_pm_read_slow(struct clocksource *cs)
85{
86 return (u64)acpi_pm_read_verified();
87}
88
89static inline void acpi_pm_need_workaround(void)
90{
91 clocksource_acpi_pm.read = acpi_pm_read_slow;
92 clocksource_acpi_pm.rating = 120;
93}
94
95/*
96 * PIIX4 Errata:
97 *
98 * The power management timer may return improper results when read.
99 * Although the timer value settles properly after incrementing,
100 * while incrementing there is a 3 ns window every 69.8 ns where the
101 * timer value is indeterminate (a 4.2% chance that the data will be
102 * incorrect when read). As a result, the ACPI free running count up
103 * timer specification is violated due to erroneous reads.
104 */
105static void acpi_pm_check_blacklist(struct pci_dev *dev)
106{
107 if (acpi_pm_good)
108 return;
109
110 /* the bug has been fixed in PIIX4M */
111 if (dev->revision < 3) {
112 pr_warn("* Found PM-Timer Bug on the chipset. Due to workarounds for a bug,\n"
113 "* this clock source is slow. Consider trying other clock sources\n");
114
115 acpi_pm_need_workaround();
116 }
117}
118DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
119 acpi_pm_check_blacklist);
120
121static void acpi_pm_check_graylist(struct pci_dev *dev)
122{
123 if (acpi_pm_good)
124 return;
125
126 pr_warn("* The chipset may have PM-Timer Bug. Due to workarounds for a bug,\n"
127 "* this clock source is slow. If you are sure your timer does not have\n"
128 "* this bug, please use \"acpi_pm_good\" to disable the workaround\n");
129
130 acpi_pm_need_workaround();
131}
132DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0,
133 acpi_pm_check_graylist);
134DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE,
135 acpi_pm_check_graylist);
136#endif
137
138#ifndef CONFIG_X86_64
139#include <asm/mach_timer.h>
140#define PMTMR_EXPECTED_RATE \
141 ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (PIT_TICK_RATE>>10))
142/*
143 * Some boards have the PMTMR running way too fast. We check
144 * the PMTMR rate against PIT channel 2 to catch these cases.
145 */
146static int verify_pmtmr_rate(void)
147{
148 u64 value1, value2;
149 unsigned long count, delta;
150
151 mach_prepare_counter();
152 value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
153 mach_countup(&count);
154 value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
155 delta = (value2 - value1) & ACPI_PM_MASK;
156
157 /* Check that the PMTMR delta is within 5% of what we expect */
158 if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
159 delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
160 pr_info("PM-Timer running at invalid rate: %lu%% of normal - aborting.\n",
161 100UL * delta / PMTMR_EXPECTED_RATE);
162 return -1;
163 }
164
165 return 0;
166}
167#else
168#define verify_pmtmr_rate() (0)
169#endif
170
171/* Number of monotonicity checks to perform during initialization */
172#define ACPI_PM_MONOTONICITY_CHECKS 10
173/* Number of reads we try to get two different values */
174#define ACPI_PM_READ_CHECKS 10000
175
176static int __init init_acpi_pm_clocksource(void)
177{
178 u64 value1, value2;
179 unsigned int i, j = 0;
180
181 if (!pmtmr_ioport)
182 return -ENODEV;
183
184 /* "verify" this timing source: */
185 for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
186 udelay(100 * j);
187 value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
188 for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
189 value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
190 if (value2 == value1)
191 continue;
192 if (value2 > value1)
193 break;
194 if ((value2 < value1) && ((value2) < 0xFFF))
195 break;
196 pr_info("PM-Timer had inconsistent results: %#llx, %#llx - aborting.\n",
197 value1, value2);
198 pmtmr_ioport = 0;
199 return -EINVAL;
200 }
201 if (i == ACPI_PM_READ_CHECKS) {
202 pr_info("PM-Timer failed consistency check (%#llx) - aborting.\n",
203 value1);
204 pmtmr_ioport = 0;
205 return -ENODEV;
206 }
207 }
208
209 if (verify_pmtmr_rate() != 0){
210 pmtmr_ioport = 0;
211 return -ENODEV;
212 }
213
214 return clocksource_register_hz(&clocksource_acpi_pm,
215 PMTMR_TICKS_PER_SEC);
216}
217
218/* We use fs_initcall because we want the PCI fixups to have run
219 * but we still need to load before device_initcall
220 */
221fs_initcall(init_acpi_pm_clocksource);
222
223/*
224 * Allow an override of the IOPort. Stupid BIOSes do not tell us about
225 * the PMTimer, but we might know where it is.
226 */
227static int __init parse_pmtmr(char *arg)
228{
229 unsigned int base;
230 int ret;
231
232 ret = kstrtouint(arg, 16, &base);
233 if (ret)
234 return ret;
235
236 pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport,
237 base);
238 pmtmr_ioport = base;
239
240 return 1;
241}
242__setup("pmtmr=", parse_pmtmr);
243