atombios question plus AMD register reference guides

Matthias Hopf mhopf at
Fri Jan 8 03:44:59 PST 2010

On Oct 13, 09 00:09:28 +0200, jfs wrote:
> i am trying to understand how the atombios parser works. i have
> been looking at both the xf86-video-ati code and the
> drivers/gpu/drm/radeon code in recent (2.6.31) linux tree.
> i pretty much get the idea, but i am stumbling on some parts.

For what it's worth - it might be helpful to take a look at my (very
simple) AtomBIOS disassembler:


> i understand this is about some indirect i/o accesses. but would
> it be possible to have a high level description of what are these
> iios and what is happening?

There is a high-level document describing the AtomBIOS language, but you
have to pester Alex for releasing it. I doubt there's anything IP
related in the docs, but you never know.

> one difficulty i have is that i find it hard to reconcile the
> registers accessed in the code with what is described in the
> various AMD register reference guides. is there some more
> documentation to look at that would give more info on the GPUs
> register layout?
> for ex, at some point the DRM code is doing a soft reset to this reg:
> r600d.h:#define R_008020_GRBM_SOFT_RESET                0x8020

Dunno about this register, but we're (still) waiting for quite some of
the docs to be released to the public we were given for radeonhd
development. There were supposed to be publicly available after some


Matthias Hopf <mhopf at>      __        __   __
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Phone +49-911-74053-715           __)  |_|  __)  |__  R & D

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