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Commit c9c57929 authored by Ravikiran G Thirumalai's avatar Ravikiran G Thirumalai Committed by Linus Torvalds
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failsafe mechanism to HPET clock calibration 



Provide a failsafe mechanism to avoid kernel spinning forever at
read_hpet_tsc during early kernel bootup.

This failsafe mechanism was originally introduced in commit
2f7a2a79, but looks like the hpet split
from time.c lost it again.

This reintroduces the failsafe mechanism

Signed-off-by: default avatarRavikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: default avatarShai Fultheim <shai@scalex86.org>
Cc: Jack Steiner <steiner@sgi.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ff99e402

arch/x86_64/kernel/hpet.c

+6 −3
Original line number Diff line number Diff line
@@ -191,6 +191,7 @@ int hpet_reenable(void) 


#define TICK_COUNT 100000000

#define TICK_MIN   5000

#define MAX_TRIES  5



/*

 * Some platforms take periodic SMI interrupts with 5ms duration. Make sure none
@@ -198,13 +199,15 @@ int hpet_reenable(void) 
 */

static void __init read_hpet_tsc(int *hpet, int *tsc)

{

	int tsc1, tsc2, hpet1;

	int tsc1, tsc2, hpet1, i;



	do {

	for (i = 0; i < MAX_TRIES; i++) {

		tsc1 = get_cycles_sync();

		hpet1 = hpet_readl(HPET_COUNTER);

		tsc2 = get_cycles_sync();

	} while (tsc2 - tsc1 > TICK_MIN);

		if (tsc2 - tsc1 > TICK_MIN)

			break;

	}

	*hpet = hpet1;

	*tsc = tsc2;

}