No video signal on iBook G4 with latest kernel

[Riccardo Mottola]

Hi Adrian,

just as a heads-up: I'm not getting a video signal with my iBook G4 with
the latest kernel. dmesg shows error messages that seem to be related to
[ 14.222735] radeon 0000:00:10.0: [drm] bpp/depth value of 16/16 not supported
[ 14.222774] radeon 0000:00:10.0: [drm] bpp/depth value of 16/16 not supported
[ 14.222780] radeon 0000:00:10.0: [drm] No compatible format found
I have reported the issue in the Freedesktop bug tracker for the radeon driver [1].

video signal of the internal LCD or external video? When does this happen
I just updated my iBook G4 14" and it works. Boot messages, console and
X11 (but read below).

I get the same error:
[   30.278787] [drm] radeon legacy LVDS backlight initialized
[   30.313728] [drm] Initialized radeon 2.50.0 20080528 for 0000:00:10.0
on minor 0
[   30.806041] radeon 0000:00:10.0: [drm] bpp/depth value of 16/16 not
supported
[   30.806115] radeon 0000:00:10.0: [drm] bpp/depth value of 16/16 not
supported
[   30.806127] radeon 0000:00:10.0: [drm] No compatible format found
[   32.182023] radeon 0000:00:10.0: [drm] fb0: radeondrmfb frame buffer
device


What happens is that perhaps you see the kernel booting, but then loose
the "login" and have a black screen (but you can type blindly?)
That happens here. I need to brighten the LCD several times until I see
something, it looks like the brightness is not correctly sync'd.
But this has been happening since a long time, it is not the latest kernel.

Riccardo

[Riccardo Mottola]

Hi Adrian,

Correct, there is an issue with the brightness controls. It sometimes randomly
turns the screen off, even when turning it to maximum setting. Then when you
change the settings again randomly, the video comes back.
Still, this needs to be bisected.

Ok... fine..  as far as I remember in my experience this is an old
bug... months. I don't ever recall it working, but previously I had a
slightly different iBook which failed in the GPU and this is not the
exact model, so subtle bugs differ (and taint my memory as far as
working goes).

On my PowerBook G4 which is quite similar, everything works regarding
the screen.

So not just "something latest" in the kernel nor it is a specific
hardware error of your computer.

Although it almost never work on boot, the amount of "increase
brightness" one needs to give is random. Could be a badly inited memory
value or so.

Riccardo