linux-kernel - Re: MFGPT in 2.6.33-rc5

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Message-ID: <20100127123850.129020d3@mycelium.queued.net>
Date:	Wed, 27 Jan 2010 12:38:50 -0500
From:	Andres Salomon <dilinger@...labora.co.uk>
To:	Jens Rottmann <JRottmann@...PERTEmbedded.de>
Cc:	Leigh Porter <leigh@...ghporter.org>,
	linux-geode@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: MFGPT in 2.6.33-rc5

On Wed, 27 Jan 2010 15:56:16 +0100
Jens Rottmann <JRottmann@...PERTEmbedded.de> wrote:

> A bit of background: The _real_ base address for the MFGPT hardware
> is set with the MSR, but this is very Geode-proprietary. So the BIOS
> contains VSA (Virtual System Architecture) code to implement a
> _virtual_ PCI device. This means the BIOS simulates a standard PCI
> device solely in software as a front-end for the MFGPT hardware to
> make it look like a 'normal' device which can be accessed with normal
> PCI drivers.
> 
> Well, this PCI device's configuration should of course always mirror
> the real state of the hardware, i.e. if someone changes the MSR, the
> PCI header should reflect that change, and vice versa.
> 
> > [    0.090015] pci 0000:00:14.0: address space collision: [io
> > 0x6200-0x63ff] already in use
> ....
> > [    0.202033] pci 0000:00:14.0: BAR 2: set to [io  0x1000-0x11ff]
> > (PCI address [0x1000-0x11ff]
> ....
> > root@...los:/home/leigh# ./mfgpt
> > 6200
> 
> Now it looks like originally both MSR and PCI say the adress is 6200.
> But Linux detects a conflict on boot and moves it to 1000 by changing
> the PCI config. At this point the BIOS should copy the new address to
> the backing MSR i.e. to the real hardware. But this it fails to do.
> And later the cs5535-mfgpt uses the address from PCI (=1000) to look
> for the MFGPTs, but they're not there - they're are still at 6200.

At least on another net5501 board, BAR0 appears to have an 8k size.
This is pretty clearly wrong, and is why there are space conflicts w/
the other BARs (consuming 0x6000 through 0x7fff, while BAR1 and BAR2
are in the 0x6100/0x6200 range).

 	Region 0: I/O ports at 6000 [size=8K]
 



> >>> Copyright (C) 2000-2007 Soekris Engineering."
> > Yup, I am about to call them. ...
> 
> Hope they fix it. But this will not be the only BIOS with this bug,
> that's why we have to revert the cs5535-mfgpt driver to read the MSR
> directly again.
> 


Indeed, thanks for the report.  This is the second email I've gotten in
the past week about net5501 bios being broken w/ the new mfgpt
stuff.  :(

CC'ing lkml to ensure others see it.  I'll write and test a patch
sometime this week.

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