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Commit 18ed61da authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86: hpet: Make WARN_ON understandable 



Andrew complained rightly that the WARN_ON in hpet_next_event() is
confusing and the code comment not really helpful.

Change it to WARN_ONCE and print the reason in clear text. Change the
comment to explain what kind of hardware wreckage we deal with.

Pointed-out-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Venki Pallipadi <venkatesh.pallipadi@intel.com>
parent c8bc6f3c

arch/x86/kernel/hpet.c

+15 −4
Original line number Original line Diff line number Diff line
@@ -384,11 +384,22 @@ static int hpet_next_event(unsigned long delta, 
	hpet_writel(cnt, HPET_Tn_CMP(timer));

	hpet_writel(cnt, HPET_Tn_CMP(timer));





	/*

	/*

	 * We need to read back the CMP register to make sure that

	 * We need to read back the CMP register on certain HPET

	 * what we wrote hit the chip before we compare it to the

	 * implementations (ATI chipsets) which seem to delay the

	 * counter.

	 * transfer of the compare register into the internal compare

	 * logic. With small deltas this might actually be too late as

	 * the counter could already be higher than the compare value

	 * at that point and we would wait for the next hpet interrupt

	 * forever. We found out that reading the CMP register back

	 * forces the transfer so we can rely on the comparison with

	 * the counter register below. If the read back from the

	 * compare register does not match the value we programmed

	 * then we might have a real hardware problem. We can not do

	 * much about it here, but at least alert the user/admin with

	 * a prominent warning.

	 */

	 */

	WARN_ON_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt);

	WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt,

		  KERN_WARNING "hpet: compare register read back failed.\n");





	return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;

	return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;

}

}