clocksource: convert x86 to generic i8253 clocksource

Convert x86 i8253 clocksource code to use generic i8253 clocksource.

Acked-by: John Stultz <john.stultz@linaro.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 4 insertions, 78 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc6c53a95bfd..01115d54c5be 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -8,6 +8,7 @@ config 64BIT
 
 config X86_32
         def_bool !64BIT
+        select CLKSRC_I8253
 
 config X86_64
         def_bool 64BIT
diff --git a/arch/x86/include/asm/i8253.h b/arch/x86/include/asm/i8253.h
index fc1f579fb965..65aaa91d5850 100644
--- a/arch/x86/include/asm/i8253.h
+++ b/arch/x86/include/asm/i8253.h
@@ -6,6 +6,8 @@
 #define PIT_CH0                 0x40
 #define PIT_CH2                 0x42
 
+#define PIT_LATCH       LATCH
+
 extern raw_spinlock_t i8253_lock;
 
 extern struct clock_event_device *global_clock_event;
diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c
index 2dfd31597443..b904dfbf6dbc 100644
--- a/arch/x86/kernel/i8253.c
+++ b/arch/x86/kernel/i8253.c
@@ -117,81 +117,6 @@ void __init setup_pit_timer(void)
 }
 
 #ifndef CONFIG_X86_64
-/*
- * Since the PIT overflows every tick, its not very useful
- * to just read by itself. So use jiffies to emulate a free
- * running counter:
- */
-static cycle_t pit_read(struct clocksource *cs)
-{
-        static int old_count;
-        static u32 old_jifs;
-        unsigned long flags;
-        int count;
-        u32 jifs;
-
-        raw_spin_lock_irqsave(&i8253_lock, flags);
-        /*
-         * Although our caller may have the read side of xtime_lock,
-         * this is now a seqlock, and we are cheating in this routine
-         * by having side effects on state that we cannot undo if
-         * there is a collision on the seqlock and our caller has to
-         * retry.  (Namely, old_jifs and old_count.)  So we must treat
-         * jiffies as volatile despite the lock.  We read jiffies
-         * before latching the timer count to guarantee that although
-         * the jiffies value might be older than the count (that is,
-         * the counter may underflow between the last point where
-         * jiffies was incremented and the point where we latch the
-         * count), it cannot be newer.
-         */
-        jifs = jiffies;
-        outb_pit(0x00, PIT_MODE);       /* latch the count ASAP */
-        count = inb_pit(PIT_CH0);       /* read the latched count */
-        count |= inb_pit(PIT_CH0) << 8;
-
-        /* VIA686a test code... reset the latch if count > max + 1 */
-        if (count > LATCH) {
-                outb_pit(0x34, PIT_MODE);
-                outb_pit(LATCH & 0xff, PIT_CH0);
-                outb_pit(LATCH >> 8, PIT_CH0);
-                count = LATCH - 1;
-        }
-
-        /*
-         * It's possible for count to appear to go the wrong way for a
-         * couple of reasons:
-         *
-         *  1. The timer counter underflows, but we haven't handled the
-         *     resulting interrupt and incremented jiffies yet.
-         *  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.)
-         *
-         * Previous attempts to handle these cases intelligently were
-         * buggy, so we just do the simple thing now.
-         */
-        if (count > old_count && jifs == old_jifs)
-                count = old_count;
-
-        old_count = count;
-        old_jifs = jifs;
-
-        raw_spin_unlock_irqrestore(&i8253_lock, flags);
-
-        count = (LATCH - 1) - count;
-
-        return (cycle_t)(jifs * LATCH) + count;
-}
-
-static struct clocksource pit_cs = {
-        .name           = "pit",
-        .rating         = 110,
-        .read           = pit_read,
-        .mask           = CLOCKSOURCE_MASK(32),
-        .mult           = 0,
-        .shift          = 20,
-};
-
 static int __init init_pit_clocksource(void)
 {
          /*
@@ -205,9 +130,7 @@ static int __init init_pit_clocksource(void)
             pit_ce.mode != CLOCK_EVT_MODE_PERIODIC)
                 return 0;
 
-        pit_cs.mult = clocksource_hz2mult(CLOCK_TICK_RATE, pit_cs.shift);
-
-        return clocksource_register(&pit_cs);
+        return clocksource_i8253_init();
 }
 arch_initcall(init_pit_clocksource);