Commit 798778b8 authored by Russell King's avatar Russell King
Browse files

clocksource: convert mips to generic i8253 clocksource 



Convert MIPS i8253 clocksource code to use generic i8253 clocksource.

Acked-by: default avatarJohn Stultz <john.stultz@linaro.org>
Acked-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 82491451

arch/mips/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -2339,6 +2339,7 @@ config MMU 


config I8253

	bool

	select CLKSRC_I8253

	select MIPS_EXTERNAL_TIMER



config ZONE_DMA32

arch/mips/include/asm/i8253.h

+5 −0
Original line number Diff line number Diff line
@@ -12,8 +12,13 @@ 
#define PIT_CH0			0x40

#define PIT_CH2			0x42



#define PIT_LATCH		LATCH



extern raw_spinlock_t i8253_lock;



extern void setup_pit_timer(void);



#define inb_pit inb_p

#define outb_pit outb_p



#endif /* __ASM_I8253_H */

arch/mips/kernel/i8253.c

+1 −77
Original line number Diff line number Diff line
@@ -125,87 +125,11 @@ void __init setup_pit_timer(void) 
	setup_irq(0, &irq0);

}



/*

 * 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)

{

	unsigned long flags;

	int count;

	u32 jifs;

	static int old_count;

	static u32 old_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_p(0x00, PIT_MODE);	/* latch the count ASAP */

	count = inb_p(PIT_CH0);	/* read the latched count */

	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;

	}



	/*

	 * 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 clocksource_pit = {

	.name	= "pit",

	.rating = 110,

	.read	= pit_read,

	.mask	= CLOCKSOURCE_MASK(32),

	.mult	= 0,

	.shift	= 20,

};



static int __init init_pit_clocksource(void)

{

	if (num_possible_cpus() > 1) /* PIT does not scale! */

		return 0;



	clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20);

	return clocksource_register(&clocksource_pit);

	return clocksource_i8253_init();

}

arch_initcall(init_pit_clocksource);