lkml.org 
[lkml]   [2007]   [May]   [21]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
DateMon, 21 May 2007 12:16:55 -0700
FromChris Wright <>
Subject[patch 43/69] i386: HPET, check if the counter works
-stable review patch.  If anyone has any objections, please let us know.
---------------------
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: Chris Wright <chrisw@sous-sol.org>
---
[chrisw: Why is this not upstream yet?]
---
 arch/i386/kernel/hpet.c |   24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)
--- linux-2.6.21.1.orig/arch/i386/kernel/hpet.c
+++ linux-2.6.21.1/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
-- 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-05-21 19:45    [from the cache]
©2003-2008