--- /dev/null
+/*
+ * 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.
+ *
+ * This file is licensed under the GPL v2.
+ */
+
+#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 cycle_t acpi_pm_read(struct clocksource *cs)
+{
+ return (cycle_t)read_pmtmr();
+}
+
+static struct clocksource clocksource_acpi_pm = {
+ .name = "acpi_pm",
+ .rating = 200,
+ .read = acpi_pm_read,
+ .mask = (cycle_t)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 cycle_t acpi_pm_read_slow(struct clocksource *cs)
+{
+ return (cycle_t)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) {
+ printk(KERN_WARNING "* 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;
+
+ printk(KERN_WARNING "* 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)
+{
+ cycle_t 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) {
+ printk(KERN_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)
+{
+ cycle_t 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;
+ printk(KERN_INFO "PM-Timer had inconsistent results:"
+ " %#llx, %#llx - aborting.\n",
+ value1, value2);
+ pmtmr_ioport = 0;
+ return -EINVAL;
+ }
+ if (i == ACPI_PM_READ_CHECKS) {
+ printk(KERN_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)
+ return ret;
+
+ pr_info("PMTMR IOPort override: 0x%04x -> 0x%04x\n", pmtmr_ioport,
+ base);
+ pmtmr_ioport = base;
+
+ return 1;
+}
+__setup("pmtmr=", parse_pmtmr);
Code Review / kvmfornfv.git / blobdiff