1 files changed, 206 insertions, 0 deletions

diff --git a/arch/i386/kernel/timers/timer_pit.c b/arch/i386/kernel/timers/timer_pit.c
new file mode 100644
index 000000000000..967d5453cd0e
--- /dev/null
+++ b/arch/i386/kernel/timers/timer_pit.c
@@ -0,0 +1,206 @@
+/*
+ * This code largely moved from arch/i386/kernel/time.c.
+ * See comments there for proper credits.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/irq.h>
+#include <linux/sysdev.h>
+#include <linux/timex.h>
+#include <asm/delay.h>
+#include <asm/mpspec.h>
+#include <asm/timer.h>
+#include <asm/smp.h>
+#include <asm/io.h>
+#include <asm/arch_hooks.h>
+
+extern spinlock_t i8259A_lock;
+extern spinlock_t i8253_lock;
+#include "do_timer.h"
+#include "io_ports.h"
+
+static int count_p; /* counter in get_offset_pit() */
+
+static int __init init_pit(char* override)
+{
+        /* check clock override */
+        if (override[0] && strncmp(override,"pit",3))
+                printk(KERN_ERR "Warning: clock= override failed. Defaulting to PIT\n");
+ 
+        count_p = LATCH;
+        return 0;
+}
+
+static void mark_offset_pit(void)
+{
+        /* nothing needed */
+}
+
+static unsigned long long monotonic_clock_pit(void)
+{
+        return 0;
+}
+
+static void delay_pit(unsigned long loops)
+{
+        int d0;
+        __asm__ __volatile__(
+                "\tjmp 1f\n"
+                ".align 16\n"
+                "1:\tjmp 2f\n"
+                ".align 16\n"
+                "2:\tdecl %0\n\tjns 2b"
+                :"=&a" (d0)
+                :"0" (loops));
+}
+
+
+/* This function must be called with xtime_lock held.
+ * It was inspired by Steve McCanne's microtime-i386 for BSD.  -- jrs
+ * 
+ * However, the pc-audio speaker driver changes the divisor so that
+ * it gets interrupted rather more often - it loads 64 into the
+ * counter rather than 11932! This has an adverse impact on
+ * do_gettimeoffset() -- it stops working! What is also not
+ * good is that the interval that our timer function gets called
+ * is no longer 10.0002 ms, but 9.9767 ms. To get around this
+ * would require using a different timing source. Maybe someone
+ * could use the RTC - I know that this can interrupt at frequencies
+ * ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
+ * it so that at startup, the timer code in sched.c would select
+ * using either the RTC or the 8253 timer. The decision would be
+ * based on whether there was any other device around that needed
+ * to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
+ * and then do some jiggery to have a version of do_timer that 
+ * advanced the clock by 1/1024 s. Every time that reached over 1/100
+ * of a second, then do all the old code. If the time was kept correct
+ * then do_gettimeoffset could just return 0 - there is no low order
+ * divider that can be accessed.
+ *
+ * Ideally, you would be able to use the RTC for the speaker driver,
+ * but it appears that the speaker driver really needs interrupt more
+ * often than every 120 us or so.
+ *
+ * Anyway, this needs more thought....          pjsg (1993-08-28)
+ * 
+ * If you are really that interested, you should be reading
+ * comp.protocols.time.ntp!
+ */
+
+static unsigned long get_offset_pit(void)
+{
+        int count;
+        unsigned long flags;
+        static unsigned long jiffies_p = 0;
+
+        /*
+         * cache volatile jiffies temporarily; we have xtime_lock. 
+         */
+        unsigned long jiffies_t;
+
+        spin_lock_irqsave(&i8253_lock, flags);
+        /* timer count may underflow right here */
+        outb_p(0x00, PIT_MODE); /* latch the count ASAP */
+
+        count = inb_p(PIT_CH0); /* read the latched count */
+
+        /*
+         * We do this guaranteed double memory access instead of a _p 
+         * postfix in the previous port access. Wheee, hackady hack
+         */
+        jiffies_t = jiffies;
+
+        count |= inb_p(PIT_CH0) << 8;
+        
+        /* VIA686a test code... reset the latch if count > max + 1 */
+        if (count > LATCH) {
+                outb_p(0x34, PIT_MODE);
+                outb_p(LATCH & 0xff, PIT_CH0);
+                outb(LATCH >> 8, PIT_CH0);
+                count = LATCH - 1;
+        }
+        
+        /*
+         * avoiding timer inconsistencies (they are rare, but they happen)...
+         * there are two kinds of problems that must be avoided here:
+         *  1. the timer counter underflows
+         *  2. hardware problem with the timer, not giving us continuous time,
+         *     the counter does small "jumps" upwards on some Pentium systems,
+         *     (see c't 95/10 page 335 for Neptun bug.)
+         */
+
+        if( jiffies_t == jiffies_p ) {
+                if( count > count_p ) {
+                        /* the nutcase */
+                        count = do_timer_overflow(count);
+                }
+        } else
+                jiffies_p = jiffies_t;
+
+        count_p = count;
+
+        spin_unlock_irqrestore(&i8253_lock, flags);
+
+        count = ((LATCH-1) - count) * TICK_SIZE;
+        count = (count + LATCH/2) / LATCH;
+
+        return count;
+}
+
+
+/* tsc timer_opts struct */
+struct timer_opts timer_pit = {
+        .name = "pit",
+        .mark_offset = mark_offset_pit, 
+        .get_offset = get_offset_pit,
+        .monotonic_clock = monotonic_clock_pit,
+        .delay = delay_pit,
+};
+
+struct init_timer_opts __initdata timer_pit_init = {
+        .init = init_pit, 
+        .opts = &timer_pit,
+};
+
+void setup_pit_timer(void)
+{
+        extern spinlock_t i8253_lock;
+        unsigned long flags;
+
+        spin_lock_irqsave(&i8253_lock, flags);
+        outb_p(0x34,PIT_MODE);          /* binary, mode 2, LSB/MSB, ch 0 */
+        udelay(10);
+        outb_p(LATCH & 0xff , PIT_CH0); /* LSB */
+        udelay(10);
+        outb(LATCH >> 8 , PIT_CH0);     /* MSB */
+        spin_unlock_irqrestore(&i8253_lock, flags);
+}
+
+static int timer_resume(struct sys_device *dev)
+{
+        setup_pit_timer();
+        return 0;
+}
+
+static struct sysdev_class timer_sysclass = {
+        set_kset_name("timer_pit"),
+        .resume = timer_resume,
+};
+
+static struct sys_device device_timer = {
+        .id     = 0,
+        .cls    = &timer_sysclass,
+};
+
+static int __init init_timer_sysfs(void)
+{
+        int error = sysdev_class_register(&timer_sysclass);
+        if (!error)
+                error = sysdev_register(&device_timer);
+        return error;
+}
+
+device_initcall(init_timer_sysfs);
+