[coreboot] AMD doesn't get it either in some ways

Idwer Vollering vidwer at gmail.com
Sat Apr 5 15:56:11 CEST 2014

2014-04-05 15:48 GMT+02:00 Luc Verhaegen <libv at skynet.be>:
> On Sat, Apr 05, 2014 at 03:20:08PM +0200, Rudolf Marek wrote:
>> Hi all,
>> I  think there is OpenRadeonBios. The problem is that thhe AtomBIOS
>> bytecode is vendor specific blob, which cannot be in principle released
>> by AMD because it is written by board manufacturers for specific wireup
>> of graphical output. This is what I have learnt when I was interested in
>> that way more.
> Iirc, this does not replace atombios in any way, just replaces the bits
> around atombios.
>> Ron, if you create dummy atombios bios whithout an x86 code the radeon
>> driver in kernel should be able to post it. It even works now. If you
>> include the orginal rom  in the cbfs but don't run it, the kernel driver
>> is able to modeset it and "post" it.  I think David Hubbard was
>> interested in the replacement BIOS as well..
> Atombios has bytecode which is run through an interpreter. There is no
> x86 code in there. All the ASIC and board specific bits should be in the
> function and data tables of atombios... But that might have changed
> already...
> Initially (for the R500), the promise was that all board specific bits
> would live in the datatables, and would not protrude into the function
> tables. but that got thrown wildly but of the window with rv610/630.
> Of course, not all things can ever be hidden away completely by
> atombios, and we had to do hard stuff ourselves still. Plus, the
> fglrx/windows driver worked around bugs in both the hw _and_ atombios.
> So who knows to what extent that rot has spread in the past 5 years,
> and to what extent the ATI VGA bios code works around atombios today?
> For all i know, ATI still doesn't allow people to flash their bioses.

Correct. Quoting Alexander Deucher:
"There is no public documentation on how to write to the flash chips
on AMD GPUs and we do not plan to expose this functionality as far as
I know." (dated April 14, 2013).

> Iirc, Biostar gave some of their users the tool to do so back in late
> 2007, and ATI was not exactly happy. So fixing shipped hardware can only
> be done through fglrx/windows driver.
> Did you know that read access to the bios was disabled from within the
> original ASIC_Init atombios function? Egbert Eich had to go and bisect
> the atombios bytecode to pinpoint what did that, as of course ATI
> couldn't or wouldn't tell us.
> Why was that important? Well, suppose you would restart your X server...
>> I think still that graphics modesetting is only minor problem. I feel
>> very disturbed about AMD plans considering to go same way as Intel. I
>> always liked AMD for opening their systems as much as possible. There was
>> always my goal to have some x86 blob free at least for the x86 CPU code.
>> This worked fine with VIA K8M890 where in VGA bios could be replaced by
>> QEMU bios ;) Now we are drifting slowly away from any truly open x86
>> system.
> Ah, the long dead and now utterly irrelevant unichrome. It spawned a
> great many things.
> Luc Verhaegen.
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