mirror of
git://projects.qi-hardware.com/openwrt-xburst.git
synced 2024-12-05 06:25:20 +02:00
321 lines
12 KiB
Diff
321 lines
12 KiB
Diff
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SCx200 High Resolution Timer Patch for Linux 2.6
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http://www.gnusto.com/scx200-hr-timer.html
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diff -Naurp linux-2.6.12-rc6.orig/arch/i386/Kconfig linux-2.6.12-rc6/arch/i386/Kconfig
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--- linux-2.6.12-rc6.orig/arch/i386/Kconfig 2005-06-07 14:56:02.000000000 +0100
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+++ linux-2.6.12-rc6/arch/i386/Kconfig 2005-06-07 16:43:19.000000000 +0100
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@@ -458,6 +458,17 @@ config HPET_EMULATE_RTC
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bool "Provide RTC interrupt"
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depends on HPET_TIMER && RTC=y
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+config SCx200HR_TIMER
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+ bool "NatSemi SCx200 27MHz High-Resolution Timer Support"
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+ help
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+ Some of the AMD (formerly National Semiconductor) Geode
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+ processors, notably the SC1100, suffer from a buggy time
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+ stamp counter which causes them to lose time when the
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+ processor is sleeping. Enable this option to use the
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+ on-board 27Mz high-resolution timer to keep time instead.
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+ depends on (SCx200)
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+ default n
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+
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config SMP
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bool "Symmetric multi-processing support"
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---help---
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diff -Naurp linux-2.6.12-rc6.orig/arch/i386/kernel/scx200.c linux-2.6.12-rc6/arch/i386/kernel/scx200.c
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--- linux-2.6.12-rc6.orig/arch/i386/kernel/scx200.c 2005-06-07 14:56:02.000000000 +0100
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+++ linux-2.6.12-rc6/arch/i386/kernel/scx200.c 2005-06-07 16:43:19.000000000 +0100
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@@ -27,6 +27,10 @@ long scx200_gpio_shadow[2];
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unsigned scx200_cb_base = 0;
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+#ifdef CONFIG_SCx200HR_TIMER
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+extern void __devinit scx200hr_timer_enable(void);
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+#endif
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+
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static struct pci_device_id scx200_tbl[] = {
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{ PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SCx200_BRIDGE) },
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{ PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SC1100_BRIDGE) },
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@@ -83,6 +87,9 @@ static int __devinit scx200_probe(struct
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printk(KERN_INFO NAME ": Configuration Block base 0x%x\n", scx200_cb_base);
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}
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+#ifdef CONFIG_SCx200HR_TIMER
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+ scx200hr_timer_enable();
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+#endif
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return 0;
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}
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diff -Naurp linux-2.6.12-rc6.orig/arch/i386/kernel/timers/Makefile linux-2.6.12-rc6/arch/i386/kernel/timers/Makefile
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--- linux-2.6.12-rc6.orig/arch/i386/kernel/timers/Makefile 2004-03-11 18:21:13.000000000 +0000
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+++ linux-2.6.12-rc6/arch/i386/kernel/timers/Makefile 2005-06-07 16:43:19.000000000 +0100
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@@ -5,5 +5,6 @@
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obj-y := timer.o timer_none.o timer_tsc.o timer_pit.o common.o
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obj-$(CONFIG_X86_CYCLONE_TIMER) += timer_cyclone.o
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+obj-$(CONFIG_SCx200HR_TIMER) += timer_scx200hr.o
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obj-$(CONFIG_HPET_TIMER) += timer_hpet.o
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obj-$(CONFIG_X86_PM_TIMER) += timer_pm.o
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diff -Naurp linux-2.6.12-rc6.orig/arch/i386/kernel/timers/timer.c linux-2.6.12-rc6/arch/i386/kernel/timers/timer.c
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--- linux-2.6.12-rc6.orig/arch/i386/kernel/timers/timer.c 2004-12-26 14:07:37.000000000 +0000
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+++ linux-2.6.12-rc6/arch/i386/kernel/timers/timer.c 2005-06-07 16:43:19.000000000 +0100
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@@ -13,6 +13,9 @@
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#endif
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/* list of timers, ordered by preference, NULL terminated */
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static struct init_timer_opts* __initdata timers[] = {
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+#ifdef CONFIG_SCx200HR_TIMER
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+ &timer_scx200hr_init,
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+#endif
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#ifdef CONFIG_X86_CYCLONE_TIMER
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&timer_cyclone_init,
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#endif
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diff -Naurp linux-2.6.12-rc6.orig/arch/i386/kernel/timers/timer_scx200hr.c linux-2.6.12-rc6/arch/i386/kernel/timers/timer_scx200hr.c
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--- linux-2.6.12-rc6.orig/arch/i386/kernel/timers/timer_scx200hr.c 1970-01-01 01:00:00.000000000 +0100
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+++ linux-2.6.12-rc6/arch/i386/kernel/timers/timer_scx200hr.c 2005-06-07 16:43:19.000000000 +0100
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@@ -0,0 +1,220 @@
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+/*
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+ * Copyright (C) 2005 Ted Phelps
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+ *
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+ * This is a clock driver for the Geode SCx200's 27MHz high-resolution
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+ * timer as the system clock replacing its buggy time stamp counter.
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+ *
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+ * Based on parts of timer_hpet.c, timer_tsc.c and timer_pit.c.
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License as
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+ * published by the Free Software Foundation; either version 2 of the
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+ * License, or (at your option) any later version.
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+ */
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+
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+#include <asm/timer.h>
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+#include <linux/init.h>
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+#include <linux/pci.h>
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+#include <linux/seq_file.h>
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+#include <linux/scx200.h>
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+
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+#define NAME "scx200hr"
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+
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+/* Read the clock */
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+#define SCx200HR_CLOCK() inl(scx200_cb_base + SCx200_TIMER_OFFSET)
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+
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+/* High-resolution timer configuration address */
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+#define SCx200_TMCNFG_OFFSET (SCx200_TIMER_OFFSET + 5)
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+
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+/* Set this bit to disable the 27 MHz input clock */
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+#define HR_TM27MPD (1 << 2)
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+
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+/* Set this bit to update the count-up timer once per cycle of the
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+ * 27MHz timer, clear it to update the timer once every 27 cycles
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+ * (effectively producing a 1MHz counter) */
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+#define HR_TMCLKSEL (1 << 1)
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+
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+/* Set this bit to enable the high-resolution timer interrupt */
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+#define HR_TMEN (1 << 0)
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+
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+/* The frequency of the timer. Change this to 27000000 and set
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+ * HR_TMCLKSEL in scx200hr_enable to run at the faster clock rate. At
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+ * this point in time there is no point in doing so since times are
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+ * recorded in usec except for the monotonic clock, which is only used
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+ * by the hangcheck-timer. */
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+#define HR_FREQ 1000000
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+
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+/* The number of cycles of the high-resolution timer we expect to see
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+ * in a single tick. Note that the result is <<8 for greater precision*/
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+#define HR_CYCLES_PER_TICK \
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+ (SH_DIV(HR_FREQ / 1000000 * TICK_NSEC, 1000, 8))
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+
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+/* The number of cycles of the high-resolution timer we expect to see
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+ * in one microsecond, <<8 */
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+#define HR_CYCLES_PER_US ((HR_FREQ / 1000000) << 8)
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+
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+
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+/* The value of the timer at the last interrupt */
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+static u32 clock_at_last_interrupt;
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+
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+/* The number of high-resolution clock cycles beyond what we would
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+ have expected that the last tick occurred, <<8 for greater precision */
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+static long clock_delay;
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+
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+/* The total number of timer nanoseconds between the time the timer
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+ * went live and the most recent tick. */
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+static unsigned long long total_ns;
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+
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+/* A lock to guard access to the monotonic clock-related variables
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+ * (total_ns and clocal_at_last_interrupt). Note that these are also
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+ * protected by the xtime lock. */
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+static seqlock_t hr_lock = SEQLOCK_UNLOCKED;
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+
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+/* Nonzero if the timer has been selected */
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+static int enable_scx200hr;
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+
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+static int __init scx200hr_init(char *override)
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+{
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+ /* Watch for a command-line clock= override */
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+ if (override[0] && strncmp(override, NAME, sizeof(NAME) - 1) != 0) {
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+ return -ENODEV;
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+ }
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+
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+ /* Note that we should try to enable this timer once the
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+ * configuration block address is known */
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+ printk(KERN_WARNING NAME ": timer not yet accessible; will probe later.\n");
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+ enable_scx200hr = 1;
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+ return -EAGAIN;
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+}
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+
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+/* Called by the timer interrupt. The xtime_lock will be held. */
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+static void mark_offset_scx200hr(void)
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+{
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+ u32 now, delta;
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+
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+ /* Avoid races between the interrupt handler and monotonic_clock */
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+ write_seqlock(&hr_lock);
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+
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+ /* Determine how many cycles have elapsed since the last interrupt */
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+ now = SCx200HR_CLOCK();
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+ delta = (now - clock_at_last_interrupt) << 8;
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+ clock_at_last_interrupt = now;
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+
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+ /* Update the total us count and remainder */
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+ total_ns += (delta * 1000) / HR_CYCLES_PER_US;
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+
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+ /* The monotonic clock is safe now */
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+ write_sequnlock(&hr_lock);
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+
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+ /* Adjust for interrupt handling delay */
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+ delta += clock_delay;
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+
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+ /* The high-resolution timer is driven by a different crystal
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+ * to the main CPU, so there's no guarantee that the 1KHz
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+ * interrupt rate will coincide with the timer. This keeps
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+ * the jiffies count in line with the high-resolution timer,
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+ * which makes it possible for NTP to do its magic */
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+ if (delta < HR_CYCLES_PER_TICK) {
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+#if 1
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+ /* Didn't go over 1000us: decrement jiffies to balance
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+ * out increment in do_timer. This will cause some
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+ * jitter if the frequency offset is large, as that
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+ * adjustment will be applied about 1ms late. */
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+ jiffies_64--;
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+ clock_delay = delta;
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+#else /* !1 */
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+ clock_delay = 0;
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+#endif /* 1 */
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+ } else if (delta < (HR_CYCLES_PER_TICK << 1) + (HR_CYCLES_PER_TICK >> 1)) {
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+ clock_delay = delta - HR_CYCLES_PER_TICK;
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+ } else {
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+ jiffies_64 += delta / HR_CYCLES_PER_TICK - 2;
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+ clock_delay = HR_CYCLES_PER_TICK + delta % HR_CYCLES_PER_TICK;
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+ }
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+}
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+
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+/* Called by gettimeofday(). Returns the number of microseconds since
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+ * the last interrupt. This is called with the xtime_lock held.*/
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+static unsigned long get_offset_scx200hr(void)
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+{
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+ u32 delta;
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+
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+ /* Get the time now and determine how many cycles have
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+ * transpired since the interrupt, adjusting for timer
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+ * interrupt jitter. */
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+ delta = ((SCx200HR_CLOCK() - clock_at_last_interrupt) << 8) + clock_delay;
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+
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+ /* Convert from cycles<<8 to microseconds */
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+ return delta / HR_CYCLES_PER_US;
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+}
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+
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+/* Returns the number of nanoseconds since the init of the timer. */
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+static unsigned long long monotonic_clock_scx200hr(void)
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+{
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+ u32 delta, seq;
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+ unsigned long long ns;
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+
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+ /* This function is *not* called with xtime_lock held, so we
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+ * need to get the hr_lock to ensure we're not competing with
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+ * mark_offset_scx200hr. */
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+ do {
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+ seq = read_seqbegin(&hr_lock);
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+ ns = total_ns;
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+ delta = SCx200HR_CLOCK() - clock_at_last_interrupt;
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+ } while (read_seqretry(&hr_lock, seq));
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+
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+ /* Convert cycles to microseconds and add. */
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+ return ns + delta * 1000 / HR_CYCLES_PER_US;
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+}
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+
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+/* scx200hr timer_opts struct */
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+struct timer_opts timer_scx200hr = {
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+ .name = NAME,
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+ .mark_offset = mark_offset_scx200hr,
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+ .get_offset = get_offset_scx200hr,
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+ .monotonic_clock = monotonic_clock_scx200hr,
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+ .delay = NULL
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+};
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+
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+/* And the init_timer struct */
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+struct init_timer_opts __devinitdata timer_scx200hr_init = {
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+ .init = scx200hr_init,
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+ .opts = &timer_scx200hr
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+};
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+
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+
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+/* Switch from the original timer to the high-resolution timer */
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+void __devinit scx200hr_timer_enable(void)
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+{
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+ /* Make sure the timer was requested and that the
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+ * configuration block is present */
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+ if (!enable_scx200hr || !scx200_cb_present()) {
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+ return;
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+ }
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+
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+ /* Reserve the timer region for ourselves */
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+ if (!request_region(scx200_cb_base + SCx200_TIMER_OFFSET,
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+ SCx200_TIMER_SIZE,
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+ "NatSemi SCx200 High-Resolution Timer")) {
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+ printk(KERN_WARNING NAME ": unable to lock timer region\n");
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+ return;
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+ }
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+
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+ /* Configure the timer */
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+ outb(0, scx200_cb_base + SCx200_TMCNFG_OFFSET);
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+
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+ /* Record the current value of the timer. */
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+ clock_at_last_interrupt = SCx200HR_CLOCK();
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+
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+ /* Get the current value of the monotonic clock */
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+ total_ns = cur_timer->monotonic_clock();
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+
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+ /* Switch from the original timer functions to ours, but keep
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+ * the current delay function since loops_per_jiffy will have
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+ * been computed using that */
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+ timer_scx200hr.delay = cur_timer->delay;
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+ cur_timer = &timer_scx200hr;
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+
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+ printk(KERN_INFO "switching to scx200 high-resolution timer (%lu cpt)\n",
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+ HR_CYCLES_PER_TICK);
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+}
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diff -Naurp linux-2.6.12-rc6.orig/include/asm-i386/timer.h linux-2.6.12-rc6/include/asm-i386/timer.h
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--- linux-2.6.12-rc6.orig/include/asm-i386/timer.h 2005-06-07 14:56:11.000000000 +0100
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+++ linux-2.6.12-rc6/include/asm-i386/timer.h 2005-06-07 16:43:19.000000000 +0100
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@@ -50,6 +50,9 @@ extern struct init_timer_opts timer_tsc_
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#ifdef CONFIG_X86_CYCLONE_TIMER
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extern struct init_timer_opts timer_cyclone_init;
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#endif
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+#ifdef CONFIG_SCx200HR_TIMER
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+extern struct init_timer_opts timer_scx200hr_init;
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+#endif
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extern unsigned long calibrate_tsc(void);
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extern void init_cpu_khz(void);
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diff -Naurp linux-2.6.12-rc6.orig/include/linux/scx200.h linux-2.6.12-rc6/include/linux/scx200.h
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--- linux-2.6.12-rc6.orig/include/linux/scx200.h 2005-06-07 14:56:11.000000000 +0100
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+++ linux-2.6.12-rc6/include/linux/scx200.h 2005-06-07 16:43:19.000000000 +0100
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@@ -32,7 +32,7 @@ extern unsigned scx200_cb_base;
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/* High Resolution Timer */
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#define SCx200_TIMER_OFFSET 0x08
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-#define SCx200_TIMER_SIZE 0x05
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+#define SCx200_TIMER_SIZE 0x06
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/* Clock Generators */
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#define SCx200_CLOCKGEN_OFFSET 0x10
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