linux-kernel - Re: HPET : Legacy Routing Replacement Enable

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Date:	Fri, 27 Oct 2006 04:42:38 +0200
From:	Andi Kleen <ak@....de>
To:	Om Narasimhan <om.turyx@...il.com>
Cc:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	linux-kernel@...r.kernel.org, randy.dunlap@...cle.com,
	clemens@...isch.de, vojtech@...e.cz, bob.picco@...com
Subject: Re: HPET : Legacy Routing Replacement Enable - 3rd try.

On Wed, Oct 25, 2006 at 02:20:22PM -0700, Om Narasimhan wrote:
> I tested against five different bioses (some with 8132, some with
> CK-804 ..etc) and I observed three different patterns.
> 
> 1. HW is LRR capable, HPET ACPI it is 1, timer interrupt is on INT2.
> Before the fix: Linux cannot get timer interrupts on INT0, goes for ACPI 
> timer.

What ACPI timer?  I don't think we have any fallback for int 0.

Not sure what you mean with INT2. Pin2 on ioapic 0 perhaps?

> After the fix : Works fine. This is according to hpet spec.

On what exact motherboard was that?

> 
> To handle case 3, I removed all references to acpi_hpet_lrr, explained
> this case in the code and decided to solely rely on the command line
> parameter for LRR capability. Rational for this approach is ,

This means the systems which you said fixes this would need the command
line parameter to work? 

> 1. At present, there are not many BIOSes which implement LRR (correctly)
> 2. People would see the bootup message (MP-BIOS bug...) if LRR is
> enabled and no timer interrupt on INT0. They can pass the hpet_lrr=1
> to make everything work fine.
> Is it the right approach?

Generally we try to work everywhere without command line parameter
unless something is terminally broken. 
-Andi
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