Radeon HD 2600 XT, DVI outputs

[Andriy Gapon]

Out of necessity I had to use an ancient Radeon HD 2600 XT card.
It has two DVI outputs (and one S-video).

I noticed a curious problem, if I attach a monitor to either of the DVI 
outputs, then initially there is video output but as soon as radeonkms 
driver attaches the monitor goes blank.
But if I attach the same monitor to either of the outputs using its VGA
input and DVI->VGA converter, then the video works fine all the time.

I tested the monitor's DVI input with a different machine and there it 
works just fine (and, as I said, it also works fine before radeonkms is 
loaded).

Here is a piece of output from the driver with the direct DVI attachment:
[drm] Radeon Display Connectors
[drm] Connector 0:
[drm]   DVI-I-1
[drm]   HPD1
[drm]   DDC: 0x7e50 0x7e50 0x7e54 0x7e54 0x7e58 0x7e58 0x7e5c 0x7e5c
[drm]   Encoders:
[drm]     DFP1: INTERNAL_KLDSCP_TMDS1
[drm]     CRT2: INTERNAL_KLDSCP_DAC2
[drm] Connector 1:
[drm]   DIN-1
[drm]   Encoders:
[drm]     TV1: INTERNAL_KLDSCP_DAC2
[drm] Connector 2:
[drm]   DVI-I-2
[drm]   HPD2
[drm]   DDC: 0x7e40 0x7e40 0x7e44 0x7e44 0x7e48 0x7e48 0x7e4c 0x7e4c
[drm]   Encoders:
[drm]     CRT1: INTERNAL_KLDSCP_DAC1
[drm]     DFP2: INTERNAL_LVTM1
drmn0: [drm] Cannot find any crtc or sizes

The same scenario with additional diagnostics: 
https://people.freebsd.org/~avg/radeon-2600-dvi-dvi.txt


And here is with the DVI->VGA configuration:
[drm] Radeon Display Connectors
[drm] Connector 0:
[drm]   DVI-I-1
[drm]   HPD1
[drm]   DDC: 0x7e50 0x7e50 0x7e54 0x7e54 0x7e58 0x7e58 0x7e5c 0x7e5c
[drm]   Encoders:
[drm]     DFP1: INTERNAL_KLDSCP_TMDS1
[drm]     CRT2: INTERNAL_KLDSCP_DAC2
[drm] Connector 1:
[drm]   DIN-1
[drm]   Encoders:
[drm]     TV1: INTERNAL_KLDSCP_DAC2
[drm] Connector 2:
[drm]   DVI-I-2
[drm]   HPD2
[drm]   DDC: 0x7e40 0x7e40 0x7e44 0x7e44 0x7e48 0x7e48 0x7e4c 0x7e4c
[drm]   Encoders:
[drm]     CRT1: INTERNAL_KLDSCP_DAC1
[drm]     DFP2: INTERNAL_LVTM1
[drm] fb mappable at 0xE0243000
[drm] vram apper at 0xE0000000
[drm] size 3145728
[drm] fb depth is 24
[drm]    pitch is 4096

The same scenario with additional diagnostics: 
https://people.freebsd.org/~avg/radeon-2600-dvi-vga.txt


Not sure if this is something with the hardware...

Thanks!
-- 
Andriy Gapon


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