linux-kernel - Re: [PATCH] Blacklist Dell Optiplex 320 from using the HPET

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Date:	Sat, 05 May 2007 16:26:54 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	john stultz <johnstul@...ibm.com>
Cc:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>,
	"Guilherme M. Schroeder" <guilherme@...tralinf.com.br>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Blacklist Dell Optiplex 320 from using the HPET

Guilherme,

On Fri, 2007-05-04 at 16:27 -0700, john stultz wrote: 
> > Before going to hard to maintain DMI black lists we should first check 
> > if it's a more general problem and can't it be solved better? Most likely
> > that system isn't the one with this issue and I don't want to apply
> > DMI patches forever.
> 
> We can give it a whirl, I just didn't want to add yet another "compare
> with some other counter that may or may not work" check. In this case,
> probably reading three times in a row and getting the same result would
> be a clearly broken box. 

can you please undo John's patch and check whether the patch below works
for you.

Thanks,

	tglx

Index: linux-2.6.21/arch/i386/kernel/hpet.c
===================================================================
--- linux-2.6.21.orig/arch/i386/kernel/hpet.c
+++ linux-2.6.21/arch/i386/kernel/hpet.c
@@ -231,6 +231,7 @@ int __init hpet_enable(void)
 {
 	unsigned long id;
 	uint64_t hpet_freq;
+	cycle_t t1;
 	u64 tmp;
 
 	if (!is_hpet_capable())
@@ -278,6 +279,14 @@ int __init hpet_enable(void)
 	/* Start the counter */
 	hpet_start_counter();
 
+	/* Verify whether hpet counter works */
+	t1 = hpet_read();
+	udelay(50);
+	if (t1 == hpet_read()) {
+		printk(KERN_WARNING "HPET counter is defect\n");
+		goto out_nohpet;
+	}
+
 	/* Initialize and register HPET clocksource
 	 *
 	 * hpet period is in femto seconds per cycle


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