could use help debugging black screen on RS780 (xf86-video-ati-6.13.0, radeon)

Larry Doolittle larry at
Wed Jun 2 22:12:50 PDT 2010

Ross -

On Wed, Jun 02, 2010 at 12:47:31PM -0400, Ross Vandegrift wrote:
> On Mon, May 31, 2010 at 09:52:37PM -0700, Larry Doolittle wrote:
> > ATI 790GX motherboard (Biostar TA790GX XE)
> > Using either Debian Squeeze (xserver-xorg-video-radeon, built
> > from xf86-video-ati-6.12.6) or home-built binary built directly
> > from xf86-video-ati-6.13.0, screens go black when I start the X
> > server.  I can still change back to a text console, at least if
> > I use the VGA port.  Using the DVI port, it seems the monitor
> > gets confused and I need to cycle the computer and/or the monitor
> > to recover.
> Do you have a second computer you could ssh in to the first to restart
> X from?

Yes.  Killing X restores the console, but restarting X from any
location still gives me a black screen.  Even when using the DVI port,
I can ctrl-alt-F1 back to the console, I just have to be patient
while the LCD monitor figures out the change in scan rates.

> I just hit this problem this morning on another computer, this time
> with an RV380.  Pretty much exactly what you describe - black screen,
> no flicker, nothing fixed it.  I was not able to switch to a text VT,
> but that hasn't worked on this box in a long time.
> I sshed in from a laptop and restarted X and that fixed it.  This
> seems new with xserver-xorg-video-radeon 1:6.12.6-1.  Haven't had a
> chance to try the fixes.

The only fix I have on my list to try is to use KMS.  A kernel is building
as I type this.  Are there any radeon driver patches, or even known
troublesome locations I could start poking at?

Compiler warnings I see when building xf86-video-ati-6.13.0 on this
amd64 machine are

radeon_accel.c: In function ‘RADEONHostDataBlit’:
radeon_accel.c:855: warning: ‘__expected’ may be used uninitialized in this function

radeon_atombios.c: In function ‘rhdAtomParseI2CRecord’:
radeon_atombios.c:1596: warning: initialization from incompatible pointer type

and a gazillion of the harmless

atombios_crtc.c: In function ‘atombios_crtc_mode_set’:
atombios_crtc.c:580: warning: dereferencing pointer ‘adp3_ptr’ does break strict-aliasing rules

   - Larry

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