[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 <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/i386/kernel/hpet.c

···
 	void __iomem* hpet_base;
 	u64 tmp;
 
-	if (!hpet_address)
+	if (!is_hpet_enabled())
 		return -ENODEV;
 
 	/* calculate the hpet address: */