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Date: Mon, 09 May 2011 14:29:22 +0100
From: Russell King - ARM Linux <linux@....linux.org.uk>
To: LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
John Stultz <johnstul@...ibm.com>
Cc: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>
Subject: [PATCH 3/4] clocksource: convert x86 to generic i8253 clocksource
Convert x86 i8253 clocksource code to use generic i8253 clocksource.
Cc: John Stultz <johnstul@...ibm.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/i8253.h | 2 +
arch/x86/kernel/i8253.c | 79 +-----------------------------------------
3 files changed, 4 insertions(+), 78 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc6c53a..01115d5 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 fc1f579..65aaa91 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 2dfd315..a97aefc 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_pit_init();
}
arch_initcall(init_pit_clocksource);
--
1.7.4.4
--
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