Bug 14754 - no VGA load detection on 3870 X2
Summary: no VGA load detection on 3870 X2
Status: RESOLVED FIXED
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/radeonhd (show other bugs)
Version: unspecified
Hardware: Other All
: medium normal
Assignee: Luc Verhaegen
QA Contact: Xorg Project Team
URL:
Whiteboard:
Keywords:
Depends on:
Blocks:
 
Reported: 2008-02-29 11:42 UTC by Joachim Deguara
Modified: 2008-03-04 13:18 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

Attachments
Xorg.0.log (129.48 KB, text/plain)
2008-02-29 11:42 UTC, Joachim Deguara 		no flags Details
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Description Joachim Deguara 2008-02-29 11:42:30 UTC 
Created attachment 14721 [details]
Xorg.0.log

Although the console works just fine with my DVI->VGA adapter (so it is not a physical problem), there seams to be a load detection problem with my 3870 X2.  DVI works just fine.

rhd_conntest says:
rhd_conntest: v1.1.0, git branch master, commit 294cf1f6 + changes
Checking connectors on 0x950F, 0x1002, 0x2542  (@05:00:00):
  Load Detection: RHD_OUTPUT_NONE
  HotPlug: RHD_HPD_1
getDDCSpeed: Clock: 825000 Prescale: 0x80e8
I2CStatus: 24
getDDCSpeed: Clock: 825000 Prescale: 0x80e8
I2CStatus: 1124
getDDCSpeed: Clock: 825000 Prescale: 0x80e8
I2CStatus: 1124
getDDCSpeed: Clock: 825000 Prescale: 0x80e8
I2CStatus: 1124
  DDC: RHD_DDC_0

and xrandr says:

DVI-I_1/digital disconnected
DVI-I_1/analog disconnected
TV_7PIN_DIN disconnected
DVI-I_2/digital connected 1280x1024+0+0 376mm x 301mm
   1280x1024      60.0*+   75.0     59.9
   1152x864       75.0     74.9
   1024x768       75.1     70.1     60.0
   832x624        74.6
   800x600        72.2     75.0     60.3
   640x480        75.0     72.8     60.0
   720x400        70.1
DVI-I_2/analog disconnected

But nothing appears on the screen and xrandr should show analog is connected and not digital, right?
Comment 1 Luc Verhaegen 2008-02-29 16:41:22 UTC 
Seems like this was just a KVM playing tricks...
Comment 2 Egbert Eich 2008-03-01 05:28:06 UTC 
Joachim, do you have a ohm-meter? maybe you can check the resistors that terminate the lines.
http://en.wikipedia.org/wiki/VGA_connector gives you the pinout.
We'd be interested in the resistance between pin 1 and 6, 2 and 7, 3 and 8.
Comment 3 Egbert Eich 2008-03-01 05:32:59 UTC 
Joachim, I meant at the inputs of the kvm switch of course.
Comment 4 Joachim Deguara 2008-03-04 13:18:41 UTC 
If I measure straight from my monitor over a VGA cable then I get 75-80 Ohms but it does fluctuate a lot.  Over the KVM (so multimeter->VGA cable->KVM->VGA cable->monitor) then I get 20-30 when I have that link selected with the KVM and without it selected I get really flucating values most in the 170 but all over the board include an open circuit load.

Mentioned this to John B and he says it is smartest to test for DDC first and then use Load as a fallback.  I see we only look at DDC when there is not HDP.

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