1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/drivers/clocksource/acpi_pm.c
4 *
5 * This file contains the ACPI PM based clocksource.
6 *
7 * This code was largely moved from the i386 timer_pm.c file
8 * which was (C) Dominik Brodowski <linux@brodo.de> 2003
9 * and contained the following comments:
10 *
11 * Driver to use the Power Management Timer (PMTMR) available in some
12 * southbridges as primary timing source for the Linux kernel.
13 *
14 * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
15 * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
16 */
17
18#include <linux/acpi_pmtmr.h>
19#include <linux/clocksource.h>
20#include <linux/timex.h>
21#include <linux/errno.h>
22#include <linux/init.h>
23#include <linux/pci.h>
24#include <linux/delay.h>
25#include <asm/io.h>
26#include <asm/time.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	if (tsc_clocksource_watchdog_disabled())
215		clocksource_acpi_pm.flags |= CLOCK_SOURCE_MUST_VERIFY;
216	return clocksource_register_hz(&clocksource_acpi_pm, PMTMR_TICKS_PER_SEC);
217}
218
219/* We use fs_initcall because we want the PCI fixups to have run
220 * but we still need to load before device_initcall
221 */
222fs_initcall(init_acpi_pm_clocksource);
223
224/*
225 * Allow an override of the IOPort. Stupid BIOSes do not tell us about
226 * the PMTimer, but we might know where it is.
227 */
228static int __init parse_pmtmr(char *arg)
229{
230	unsigned int base;
231	int ret;
232
233	ret = kstrtouint(arg, 16, &base);
234	if (ret) {
235		pr_warn("PMTMR: invalid 'pmtmr=' value: '%s'\n", arg);
236		return 1;
237	}
238
239	pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport,
240		base);
241	pmtmr_ioport = base;
242
243	return 1;
244}
245__setup("pmtmr=", parse_pmtmr);
246