radeon problems with current cvs code

[Benjamin Herrenschmidt]

> > Load DRM with option no_wb=1
> what is it for and how do I do it?

Well... it tells your DRM to not try to do writeback through AGP (that
is to not let the video card write various status informations back to
memory via the AGP bus). Doing AGP writeback is faster, but on some
chipsets, it doesn't work properly. The driver tries to detect it, but
we had some examples in the past where the detection would say "ok"
while it's still unreliable. This option forces not to do it. To do
that, you either:

  modprobe radeon no_wb=1

(Or edit the appropriate modultils config file to have that option by
default)

Or if the module is built-in the kernel, boot the kernel with

  radeon.no_wb=1

On the kernel comand line.

> > Try latest DRM CVS
> I have kernel 2.6.16. I saw that source files such as radeon.c
> were identical to the ones in DRM CVS. Am I wrong?

There is no such file as radeon.c that I can remember :) the drm CVS has
a slightly more up to date version than 2.6.16. To build it in linux, go
to linux-core and type

 make DRM_MODULES="radeon"

> At the moment I have a kernel compiled without module support.
> And the radeon drm is built-in. Do I have to change that?

If it works for you, stay with it.

> At the moment it works, but xgl is slow with movies.
> I saw this sentence in the suse site:
> 
> Driver has neither pBuffer nor FBO support. When using a composite
> manager all windows are rendered in software and only compositing is
> hardware accelerated. Astonishingly, this works well enough for most
> use cases.
> 
> What does it mean? That is, is the driver _never_ going to have that support?

It will, just no yet. It's beeing developped on intel chipsets at the
moment and will probably be ported over at one point. I can't tell more
precisely.

Ben.