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Subject[2.6.22.2 review 46/84] i386: HPET, check if the counter works
From: Thomas Gleixner <tglx@linutronix.de>

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>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/i386/kernel/hpet.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
--- a/arch/i386/kernel/hpet.c
+++ b/arch/i386/kernel/hpet.c
@@ -226,7 +226,8 @@ 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;
@@ -273,6 +274,27 @@ 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
--
-
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