[patch 16/28] HPET: make minimum reprogramming delta useful

[Greg KH]

2.6.25-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

commit 7cfb0435330364f90f274a26ecdc5f47f738498c upstream

The minimum reprogramming delta was hardcoded in HPET ticks,
which is stupid as it does not work with faster running HPETs.
The C1E idle patches made this prominent on AMD/RS690 chipsets,
where the HPET runs with 25MHz. Set it to 5us which seems to be
a reasonable value and fixes the problems on the bug reporters
machines. We have a further sanity check now in the clock events,
which increases the delta when it is not sufficient.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Luiz Fernando N. Capitulino <lcapitulino@xxxxxxxxxxxxxxx>
Tested-by: Dmitry Nezhevenko <dion@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/x86/kernel/hpet.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -222,8 +222,8 @@ static void hpet_legacy_clockevent_regis
 	/* Calculate the min / max delta */
 	hpet_clockevent.max_delta_ns = clockevent_delta2ns(0x7FFFFFFF,
 							   &hpet_clockevent);
-	hpet_clockevent.min_delta_ns = clockevent_delta2ns(0x30,
-							   &hpet_clockevent);
+	/* 5 usec minimum reprogramming delta. */
+	hpet_clockevent.min_delta_ns = 5000;
 
 	/*
 	 * Start hpet with the boot cpu mask and make it

-- 
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