1 files changed, 258 insertions, 0 deletions
diff --git a/arch/i386/kernel/timers/timer_pm.c b/arch/i386/kernel/timers/timer_pm.c
new file mode 100644
index 0000000..d77f220
--- /dev/null
+++ b/arch/i386/kernel/timers/timer_pm.c
@@ -0,0 +1,258 @@
+/*
+ * (C) Dominik Brodowski <linux@brodo.de> 2003
+ *
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <asm/types.h>
+#include <asm/timer.h>
+#include <asm/smp.h>
+#include <asm/io.h>
+#include <asm/arch_hooks.h>
+
+#include <linux/timex.h>
+#include "mach_timer.h"
+
+/* Number of PMTMR ticks expected during calibration run */
+#define PMTMR_TICKS_PER_SEC 3579545
+#define PMTMR_EXPECTED_RATE \
+  ((CALIBRATE_LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
+
+
+/* The I/O port the PMTMR resides at.
+ * The location is detected during setup_arch(),
+ * in arch/i386/acpi/boot.c */
+u32 pmtmr_ioport = 0;
+
+
+/* value of the Power timer at last timer interrupt */
+static u32 offset_tick;
+static u32 offset_delay;
+
+static unsigned long long monotonic_base;
+static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
+
+#define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
+
+/*helper function to safely read acpi pm timesource*/
+static inline u32 read_pmtmr(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 time
+	 * source is not latched, so you must read it multiple
+	 * times to insure a safe value is read.
+	 */
+	do {
+		v1 = inl(pmtmr_ioport);
+		v2 = inl(pmtmr_ioport);
+		v3 = inl(pmtmr_ioport);
+	} while ((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
+			|| (v3 > v1 && v3 < v2));
+
+	/* mask the output to 24 bits */
+	return v2 & ACPI_PM_MASK;
+}
+
+
+/*
+ * 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)
+{
+	u32 value1, value2;
+	unsigned long count, delta;
+
+	mach_prepare_counter();
+	value1 = read_pmtmr();
+	mach_countup(&count);
+	value2 = read_pmtmr();
+	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;
+}
+
+
+static int init_pmtmr(char* override)
+{
+	u32 value1, value2;
+	unsigned int i;
+
+ 	if (override[0] && strncmp(override,"pmtmr",5))
+		return -ENODEV;
+
+	if (!pmtmr_ioport)
+		return -ENODEV;
+
+	/* we use the TSC for delay_pmtmr, so make sure it exists */
+	if (!cpu_has_tsc)
+		return -ENODEV;
+
+	/* "verify" this timing source */
+	value1 = read_pmtmr();
+	for (i = 0; i < 10000; i++) {
+		value2 = read_pmtmr();
+		if (value2 == value1)
+			continue;
+		if (value2 > value1)
+			goto pm_good;
+		if ((value2 < value1) && ((value2) < 0xFFF))
+			goto pm_good;
+		printk(KERN_INFO "PM-Timer had inconsistent results: 0x%#x, 0x%#x - aborting.\n", value1, value2);
+		return -EINVAL;
+	}
+	printk(KERN_INFO "PM-Timer had no reasonable result: 0x%#x - aborting.\n", value1);
+	return -ENODEV;
+
+pm_good:
+	if (verify_pmtmr_rate() != 0)
+		return -ENODEV;
+
+	init_cpu_khz();
+	return 0;
+}
+
+static inline u32 cyc2us(u32 cycles)
+{
+	/* The Power Management Timer ticks at 3.579545 ticks per microsecond.
+	 * 1 / PM_TIMER_FREQUENCY == 0.27936511 =~ 286/1024 [error: 0.024%]
+	 *
+	 * Even with HZ = 100, delta is at maximum 35796 ticks, so it can
+	 * easily be multiplied with 286 (=0x11E) without having to fear
+	 * u32 overflows.
+	 */
+	cycles *= 286;
+	return (cycles >> 10);
+}
+
+/*
+ * this gets called during each timer interrupt
+ *   - Called while holding the writer xtime_lock
+ */
+static void mark_offset_pmtmr(void)
+{
+	u32 lost, delta, last_offset;
+	static int first_run = 1;
+	last_offset = offset_tick;
+
+	write_seqlock(&monotonic_lock);
+
+	offset_tick = read_pmtmr();
+
+	/* calculate tick interval */
+	delta = (offset_tick - last_offset) & ACPI_PM_MASK;
+
+	/* convert to usecs */
+	delta = cyc2us(delta);
+
+	/* update the monotonic base value */
+	monotonic_base += delta * NSEC_PER_USEC;
+	write_sequnlock(&monotonic_lock);
+
+	/* convert to ticks */
+	delta += offset_delay;
+	lost = delta / (USEC_PER_SEC / HZ);
+	offset_delay = delta % (USEC_PER_SEC / HZ);
+
+
+	/* compensate for lost ticks */
+	if (lost >= 2)
+		jiffies_64 += lost - 1;
+
+	/* don't calculate delay for first run,
+	   or if we've got less then a tick */
+	if (first_run || (lost < 1)) {
+		first_run = 0;
+		offset_delay = 0;
+	}
+}
+
+
+static unsigned long long monotonic_clock_pmtmr(void)
+{
+	u32 last_offset, this_offset;
+	unsigned long long base, ret;
+	unsigned seq;
+
+
+	/* atomically read monotonic base & last_offset */
+	do {
+		seq = read_seqbegin(&monotonic_lock);
+		last_offset = offset_tick;
+		base = monotonic_base;
+	} while (read_seqretry(&monotonic_lock, seq));
+
+	/* Read the pmtmr */
+	this_offset =  read_pmtmr();
+
+	/* convert to nanoseconds */
+	ret = (this_offset - last_offset) & ACPI_PM_MASK;
+	ret = base + (cyc2us(ret) * NSEC_PER_USEC);
+	return ret;
+}
+
+static void delay_pmtmr(unsigned long loops)
+{
+	unsigned long bclock, now;
+
+	rdtscl(bclock);
+	do
+	{
+		rep_nop();
+		rdtscl(now);
+	} while ((now-bclock) < loops);
+}
+
+
+/*
+ * get the offset (in microseconds) from the last call to mark_offset()
+ *	- Called holding a reader xtime_lock
+ */
+static unsigned long get_offset_pmtmr(void)
+{
+	u32 now, offset, delta = 0;
+
+	offset = offset_tick;
+	now = read_pmtmr();
+	delta = (now - offset)&ACPI_PM_MASK;
+
+	return (unsigned long) offset_delay + cyc2us(delta);
+}
+
+
+/* acpi timer_opts struct */
+static struct timer_opts timer_pmtmr = {
+	.name			= "pmtmr",
+	.mark_offset		= mark_offset_pmtmr,
+	.get_offset		= get_offset_pmtmr,
+	.monotonic_clock 	= monotonic_clock_pmtmr,
+	.delay 			= delay_pmtmr,
+};
+
+struct init_timer_opts __initdata timer_pmtmr_init = {
+	.init = init_pmtmr,
+	.opts = &timer_pmtmr,
+};
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
+MODULE_DESCRIPTION("Power Management Timer (PMTMR) as primary timing source for x86");