Radeon HD 2600 XT, DVI outputs

[Andriy Gapon]

On 2022-08-16 12:01, Christian König wrote:
> Hi Andriy,
> 
> well first of all can you please test that with Linux? If this works on 
> Linux then there is probably just something missing on the FreeBSD port.

Thank you for the suggestion.  This is something that I should have 
tested from the start.  But I was overly confident that the problem 
could not be a port problem as the hardware is so ancient and the port 
exists for quite a long while and it's currently on the Linux 5.10 level.

But, yes, it is a port problem after all.  I tested Debian with 5.10 
kernel and the problem does not exist there.

Here are some log messages from Linux:
[  397.379974] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:46:DVI-I-1]
[  397.395520] [drm:radeon_atom_dac_detect [radeon]] Bios 0 scratch 
20000 00000014
[  397.395534] [drm:radeon_atombios_connected_scratch_regs [radeon]] 
DFP1 disconnected
[  397.395546] [drm:radeon_atombios_connected_scratch_regs [radeon]] 
CRT2 disconnected
[  397.395550] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:46:DVI-I-1] status updated from unknown to 
disconnected
[  397.395553] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:46:DVI-I-1] disconnected
[  397.395557] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:48:DIN-1]
[  397.411838] [drm:radeon_atom_dac_detect [radeon]] Bios 0 scratch 
20000 00000014
[  397.411856] [drm:radeon_atombios_connected_scratch_regs [radeon]] TV1 
disconnected
[  397.411864] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:48:DIN-1] status updated from unknown to 
disconnected
[  397.411867] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:48:DIN-1] disconnected
[  397.411873] [drm:drm_helper_probe_single_connector_modes 
[drm_kms_helper]] [CONNECTOR:50:DVI-I-2]
[  397.446829] [drm:drm_add_display_info [drm]] Supported Monitor 
Refresh rate range is 0 Hz - 0 Hz
[  397.446833] [drm:drm_add_display_info [drm]] non_desktop set to 0
[  397.446845] [drm:radeon_atombios_connected_scratch_regs [radeon]] 
CRT1 disconnected
[  397.446855] [drm:radeon_atombios_connected_scratch_regs [radeon]] 
DFP2 connected

I guess that this tells us that the monitor (DVI-I-2 + DFP2) is detected 
using some other method, so the detection does need to invoke 
radeon_atom_dac_detect for it.

I guess that radeon_dvi_detect() is what is responsible for detecting 
DVI monitor connections.  So, it looks like the difference could be in 
DDC / EDID probing.


> Am 16.08.22 um 10:48 schrieb 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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