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authorThomas Gleixner <tglx@linutronix.de>2007-07-21 17:11:12 +0200
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-21 18:37:12 -0700
commit075bcd1f9726b8a1caff86eda06f29f71fb21235 (patch)
tree992a8717dbe7b17fa80cd10f47c3dc639f395aa2 /arch
parentdf2edcf3b6ba54d9ffa620e322583cd994a6e54a (diff)
i386: HPET, check if the counter works
Some systems have a HPET which is not incrementing, which leads to a complete hang. Detect it during HPET setup. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: john stultz <johnstul@us.ibm.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/i386/kernel/hpet.c24
1 files changed, 23 insertions, 1 deletions
diff --git a/arch/i386/kernel/hpet.c b/arch/i386/kernel/hpet.c
index 662d7976a9e..b93310d1195 100644
--- a/arch/i386/kernel/hpet.c
+++ b/arch/i386/kernel/hpet.c
@@ -232,7 +232,8 @@ int __init hpet_enable(void)
{
unsigned long id;
uint64_t hpet_freq;
- u64 tmp;
+ u64 tmp, start, now;
+ cycle_t t1;
if (!is_hpet_capable())
return 0;
@@ -279,6 +280,27 @@ int __init hpet_enable(void)
/* Start the counter */
hpet_start_counter();
+ /* Verify whether hpet counter works */
+ t1 = read_hpet();
+ rdtscll(start);
+
+ /*
+ * We don't know the TSC frequency yet, but waiting for
+ * 200000 TSC cycles is safe:
+ * 4 GHz == 50us
+ * 1 GHz == 200us
+ */
+ do {
+ rep_nop();
+ rdtscll(now);
+ } while ((now - start) < 200000UL);
+
+ if (t1 == read_hpet()) {
+ printk(KERN_WARNING
+ "HPET counter not counting. HPET disabled\n");
+ goto out_nohpet;
+ }
+
/* Initialize and register HPET clocksource
*
* hpet period is in femto seconds per cycle