linux-kernel - Re: [PATCH v2] hpet: Enable hidden HPET on NVidia motherboards

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Message-ID: <20070416214042.GB25508@one.firstfloor.org>
Date:	Mon, 16 Apr 2007 23:40:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Mikko Tiihonen <mikko.tiihonen@....fi>
Cc:	Andi Kleen <andi@...stfloor.org>, clemens@...isch.de,
	bob.picco@...com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Currid <ACurrid@...dia.com>
Subject: Re: [PATCH v2] hpet: Enable hidden HPET on NVidia motherboards

On Tue, Apr 17, 2007 at 12:28:31AM +0300, Mikko Tiihonen wrote:
> I actually was more worried that someone might complain that the pci 
> scanning is copy & paste code from end of the same file. I did try to use 
> the generic pci functions first but because they insist on enabling 
> interrupts they cannot be used this early. And this code needs to be run 
> before the timer initialization.

Yes that's the issue. You're adding another PCI scanner copy'n'pasted
from the caller of the function you're adding it to. See the problem?

> If you want I can submit a separate patch to move the ... not nice pci 
> scanning code to pci directory under some early_pci_scan(u32 *pci_ids, 
> hook) function. The same code was already cut&pasted in 

That is what early-quirks is anyways. But the way to scan for multple
things is not to add anther recursive scan, but to just extend or
change the main loop.

> >Also there should be done anything here without confirmation from
> >Nvidia that HPET is actually supposed to work. Sometimes hardware
> >is disabled by BIOS because it is seriously broken (there was at least
> >one other chipset that could corrupt your flash if you force enabled
> >HPET in some steppings)
> 
> I hope someone has some secret contacts at NVidia because they have not 
> been very open with their chipsets. I looked at LinuxBios and their NForce4 
> chipset code had just had commented out code that wrote to 0x44 register. 
> So obviously something more is needed.

Andy, can you help please?  There is interest in force enabling HPET on
boards where the BIOS didn't chose too. We would need a list of PCI-IDs
where this is safe to do and what bits to poke. Thanks.

-Andi
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