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>

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