[PATCH] Fix faulty HPET clocksource usage (fix for bug #7062)

Apparently some systems export valid HPET addresses, but hpet_enable()
fails.  Then when the HPET clocksource starts up, it only checks for a
valid HPET address, and the result is a system where time does not advance.

See http://bugme.osdl.org/show_bug.cgi?id=7062 for details.

This patch just makes sure we better check that the HPET is functional
before registering the HPET clocksource.
Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/hpet.c

@@ -35,7 +35,7 @@ static int __init init_hpet_clocksource(void)
 	void __iomem* hpet_base;
 	u64 tmp;
 
-	if (!hpet_address)
+	if (!is_hpet_enabled())
 		return -ENODEV;
 
 	/* calculate the hpet address: */