[Bug 16055] Blank screen with Radeon 9600 / RV350

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=16055





--- Comment #14 from Peter Williams <peter at newton.cx>  2008-10-16 00:53:11 PST ---
I've finally gotten the chance to take a further look at debugging what's going
on inside the driver. I'm using git master of the X server, xf86-video-ati, and
their relevant dependencies.

As a side question, it seems like in my situation, DVI-1 is connected to Port0
and DVI-0 is connected to Port1. Is that plausible?

As far as I can figure out, there are three problems here:

* Without a "Virtual 2560 1600" line, the server chooses a bogus mode to try to
use. When I first reported the bug, it was 1152x864; now it's 1600x1200; it
should be using the monitor's other reported mode, 1280x800.

* If I force 1280x800 and use DVI-1, I get what may be the right resolution,
but my colors are totally messed up.

* If I enable 2560x1600, nothing happens since it seems that the TMDS isn't set
up into dual-link mode correctly.

I'm focusing on the second problem at the moment. I imagine that maybe some
piece of hardware isn't getting set up correctly here. If I step through
legacy_output_mode_set, eventually there's a call to
RADEONInitExtTMDSInfoFromBIOS, which was mentioned to me as a function to look
at. There are some calls to RADEONDVOWriteByte that fail and show up in my
logs:

i2c write: 0xe, 0x0
(EE) RADEON(0): Unable to write to DVO Slave 112.
i2c write: 0x8, 0x39
(EE) RADEON(0): Unable to write to DVO Slave 112.
i2c write: 0x9, 0x38
(EE) RADEON(0): Unable to write to DVO Slave 112.
i2c write: 0xa, 0x90
(EE) RADEON(0): Unable to write to DVO Slave 112.
i2c write: 0xc, 0x89
(EE) RADEON(0): Unable to write to DVO Slave 112.
i2c write: 0x33, 0x0
(EE) RADEON(0): Unable to write to DVO Slave 112.
i2c write: 0xd, 0x0
(EE) RADEON(0): Unable to write to DVO Slave 112.

Might these messages be related to what I'm seeing, or should I look elsewhere?

(There is some promise for the third problem of setting up the TMDS in
dual-link mode. In RADEONInitFP2Registers, I see:

if (IS_R300_VARIANT) {
  ...
#if 0
  if (mode->Clock > 165000)
     save->fp2_gen_cntl |= R300_FP2_DVO_DUAL_CHANNEL_EN;
#endif
}

Is there an explanation for why those lines are commented out? It sounds like
that bit might be exactly what I need. But, again, I'd like to get 1280x800
working before working on 2560x1600.)


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