1 files changed, 243 insertions, 0 deletions
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
new file mode 100644
index 000000000..279ddff81
--- /dev/null
+++ b/drivers/clocksource/acpi_pm.c
@@ -0,0 +1,243 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/drivers/clocksource/acpi_pm.c
+ *
+ * This file contains the ACPI PM based clocksource.
+ *
+ * This code was largely moved from the i386 timer_pm.c file
+ * which was (C) Dominik Brodowski <linux@brodo.de> 2003
+ * and contained the following comments:
+ *
+ * Driver to use the Power Management Timer (PMTMR) available in some
+ * southbridges as primary timing source for the Linux kernel.
+ *
+ * Based on parts of linux/drivers/acpi/hardware/hwtimer.c, timer_pit.c,
+ * timer_hpet.c, and on Arjan van de Ven's implementation for 2.4.
+ */
+
+#include <linux/acpi_pmtmr.h>
+#include <linux/clocksource.h>
+#include <linux/timex.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/pci.h>
+#include <linux/delay.h>
+#include <asm/io.h>
+
+/*
+ * The I/O port the PMTMR resides at.
+ * The location is detected during setup_arch(),
+ * in arch/i386/kernel/acpi/boot.c
+ */
+u32 pmtmr_ioport __read_mostly;
+
+static inline u32 read_pmtmr(void)
+{
+	/* mask the output to 24 bits */
+	return inl(pmtmr_ioport) & ACPI_PM_MASK;
+}
+
+u32 acpi_pm_read_verified(void)
+{
+	u32 v1 = 0, v2 = 0, v3 = 0;
+
+	/*
+	 * It has been reported that because of various broken
+	 * chipsets (ICH4, PIIX4 and PIIX4E) where the ACPI PM clock
+	 * source is not latched, you must read it multiple
+	 * times to ensure a safe value is read:
+	 */
+	do {
+		v1 = read_pmtmr();
+		v2 = read_pmtmr();
+		v3 = read_pmtmr();
+	} while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
+			  || (v3 > v1 && v3 < v2)));
+
+	return v2;
+}
+
+static u64 acpi_pm_read(struct clocksource *cs)
+{
+	return (u64)read_pmtmr();
+}
+
+static struct clocksource clocksource_acpi_pm = {
+	.name		= "acpi_pm",
+	.rating		= 200,
+	.read		= acpi_pm_read,
+	.mask		= (u64)ACPI_PM_MASK,
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+
+#ifdef CONFIG_PCI
+static int acpi_pm_good;
+static int __init acpi_pm_good_setup(char *__str)
+{
+	acpi_pm_good = 1;
+	return 1;
+}
+__setup("acpi_pm_good", acpi_pm_good_setup);
+
+static u64 acpi_pm_read_slow(struct clocksource *cs)
+{
+	return (u64)acpi_pm_read_verified();
+}
+
+static inline void acpi_pm_need_workaround(void)
+{
+	clocksource_acpi_pm.read = acpi_pm_read_slow;
+	clocksource_acpi_pm.rating = 120;
+}
+
+/*
+ * PIIX4 Errata:
+ *
+ * The power management timer may return improper results when read.
+ * Although the timer value settles properly after incrementing,
+ * while incrementing there is a 3 ns window every 69.8 ns where the
+ * timer value is indeterminate (a 4.2% chance that the data will be
+ * incorrect when read). As a result, the ACPI free running count up
+ * timer specification is violated due to erroneous reads.
+ */
+static void acpi_pm_check_blacklist(struct pci_dev *dev)
+{
+	if (acpi_pm_good)
+		return;
+
+	/* the bug has been fixed in PIIX4M */
+	if (dev->revision < 3) {
+		pr_warn("* Found PM-Timer Bug on the chipset. Due to workarounds for a bug,\n"
+			"* this clock source is slow. Consider trying other clock sources\n");
+
+		acpi_pm_need_workaround();
+	}
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82371AB_3,
+			acpi_pm_check_blacklist);
+
+static void acpi_pm_check_graylist(struct pci_dev *dev)
+{
+	if (acpi_pm_good)
+		return;
+
+	pr_warn("* The chipset may have PM-Timer Bug. Due to workarounds for a bug,\n"
+		"* this clock source is slow. If you are sure your timer does not have\n"
+		"* this bug, please use \"acpi_pm_good\" to disable the workaround\n");
+
+	acpi_pm_need_workaround();
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_82801DB_0,
+			acpi_pm_check_graylist);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SERVERWORKS, PCI_DEVICE_ID_SERVERWORKS_LE,
+			acpi_pm_check_graylist);
+#endif
+
+#ifndef CONFIG_X86_64
+#include <asm/mach_timer.h>
+#define PMTMR_EXPECTED_RATE \
+  ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (PIT_TICK_RATE>>10))
+/*
+ * Some boards have the PMTMR running way too fast. We check
+ * the PMTMR rate against PIT channel 2 to catch these cases.
+ */
+static int verify_pmtmr_rate(void)
+{
+	u64 value1, value2;
+	unsigned long count, delta;
+
+	mach_prepare_counter();
+	value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
+	mach_countup(&count);
+	value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
+	delta = (value2 - value1) & ACPI_PM_MASK;
+
+	/* Check that the PMTMR delta is within 5% of what we expect */
+	if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
+	    delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
+		pr_info("PM-Timer running at invalid rate: %lu%% of normal - aborting.\n",
+			100UL * delta / PMTMR_EXPECTED_RATE);
+		return -1;
+	}
+
+	return 0;
+}
+#else
+#define verify_pmtmr_rate() (0)
+#endif
+
+/* Number of monotonicity checks to perform during initialization */
+#define ACPI_PM_MONOTONICITY_CHECKS 10
+/* Number of reads we try to get two different values */
+#define ACPI_PM_READ_CHECKS 10000
+
+static int __init init_acpi_pm_clocksource(void)
+{
+	u64 value1, value2;
+	unsigned int i, j = 0;
+
+	if (!pmtmr_ioport)
+		return -ENODEV;
+
+	/* "verify" this timing source: */
+	for (j = 0; j < ACPI_PM_MONOTONICITY_CHECKS; j++) {
+		udelay(100 * j);
+		value1 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
+		for (i = 0; i < ACPI_PM_READ_CHECKS; i++) {
+			value2 = clocksource_acpi_pm.read(&clocksource_acpi_pm);
+			if (value2 == value1)
+				continue;
+			if (value2 > value1)
+				break;
+			if ((value2 < value1) && ((value2) < 0xFFF))
+				break;
+			pr_info("PM-Timer had inconsistent results: %#llx, %#llx - aborting.\n",
+				value1, value2);
+			pmtmr_ioport = 0;
+			return -EINVAL;
+		}
+		if (i == ACPI_PM_READ_CHECKS) {
+			pr_info("PM-Timer failed consistency check  (%#llx) - aborting.\n",
+				value1);
+			pmtmr_ioport = 0;
+			return -ENODEV;
+		}
+	}
+
+	if (verify_pmtmr_rate() != 0){
+		pmtmr_ioport = 0;
+		return -ENODEV;
+	}
+
+	return clocksource_register_hz(&clocksource_acpi_pm,
+						PMTMR_TICKS_PER_SEC);
+}
+
+/* We use fs_initcall because we want the PCI fixups to have run
+ * but we still need to load before device_initcall
+ */
+fs_initcall(init_acpi_pm_clocksource);
+
+/*
+ * Allow an override of the IOPort. Stupid BIOSes do not tell us about
+ * the PMTimer, but we might know where it is.
+ */
+static int __init parse_pmtmr(char *arg)
+{
+	unsigned int base;
+	int ret;
+
+	ret = kstrtouint(arg, 16, &base);
+	if (ret) {
+		pr_warn("PMTMR: invalid 'pmtmr=' value: '%s'\n", arg);
+		return 1;
+	}
+
+	pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport,
+		base);
+	pmtmr_ioport = base;
+
+	return 1;
+}
+__setup("pmtmr=", parse_pmtmr);