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Old 07-10-07, 07:57 AM   #1
Lelfe
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Default Dual/Single Link TMDS

Hello

I've got a strange error concerning DVI link detection with my Quadro cards.
Here is my configuration :

--Config--
- Some machines (A) with Quadro 3400
- Some machines (B) with Quadro 4500
- a Dell 2001FP for tests
- and a DVI switch MatrixPro from Barco. ( http://www.barco.com/corporate/en/pr...p?element=3012 )
- tests were done with drivers 8762 and 9631 (same behaviour)


--Purpose--
I want to plug the Dell to the DVI switch, and use the machines (A&B) as data input for it, using the MatrixPro for switching.

--
Currently, everything works fine if i plug the Dell directly to the graphic cards with a Single Link DVI-D.

--
The problem is the X server is unable to read the EDID info from the matrix (even if this hardware supports this).
I've got the very strange following behaviour :
- I plug the Dell directly, I start the X server, everything is ok. I unplugged the Dell from the PC, plug it to the DVI switch, and plug the DVI switch to the PC. Everythink is still ok.
- If I restart the X server with the DVI switch used, i've got no image on the screen.

To workaround this, I decided to disable the EDID detection in X config file, and set all the informations using NVidia driver options. Doing this, it still works fine with the Dell directly plug, but doesn't when using the dvi switch.

After analysing, the X server log in verbose mode, i notice that the only difference is :

When it works:
Code:
(--) NVIDIA(0): DFP-0: Internal Dual Link TMDS
(--) NVIDIA(0): DFP-0: Native FlatPanel Scaling is supported
When it does not work:
Code:
(--) NVIDIA(0): DFP-0: Internal Single Link TMDS
(--) NVIDIA(0): DFP-0: Native FlatPanel Scaling is not supported
And I made other verification, every time it works, it is detected as a Dual link, and every time it does not, it is detected as a Single Link, even if all the cables are Single Link only (DVI-D) !

Is it possible to force the dual link mode ?
Do you have a clue why the EDID data are not read ?
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Old 07-10-07, 08:03 AM   #2
Lelfe
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Default Re: Dual/Single Link TMDS

Unfortunately, for security reason, it really difficult for me to provide a nvidia error bug log. Please tell me as much as you can with the provided informations, if a particular info is needed, i'll try to provide it, but it is really a problem for me to provide the full log.
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Old 07-10-07, 10:21 AM   #3
netllama
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Default Re: Dual/Single Link TMDS

No, you cannot force dual link TMDS. Without seeing a detailed bug report, its not really possible to guess why the EDID isn't being seen consistently. It might be a hardware problem, or it might be a driver problem.

Both 1.0-8762 and 1.0-9631 are no longer supported, so I'd suggest updating to 100.14.11 and retesting.
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Old 07-10-07, 10:34 AM   #4
plesch
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Default Re: Dual/Single Link TMDS

Hello,

as a not very elegant workaround, you could save the EDID of the DFP in a file while it is directly connected to the Quadro, using nvidia-settings. Then use the xorg.conf option to load that EDID from the file rather than getting it directly from the connected hardware while the switch is connected. It worked for me but there is a recent forum thread which discusses situations where saved EDIDs in a file were rejected by the driver as well.

I had a somewhat related problem. I first tried to reconstruct a modeline from the working EDID and the verbose log but in the end was only be able to use an analog connection with such a custom modeline.

Hope this helps,

Andreas
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Old 07-10-07, 10:36 AM   #5
plesch
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Default Re: Dual/Single Link TMDS

Quote:
Originally Posted by Lelfe
Unfortunately, for security reason, it really difficult for me to provide a nvidia error bug log. Please tell me as much as you can with the provided informations, if a particular info is needed, i'll try to provide it, but it is really a problem for me to provide the full log.
I used sed 's/critical_info//g' to sanitize bug reports. They contain all sorts of stuff.

Andreas
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Old 07-10-07, 11:12 AM   #6
pe1chl
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Default Re: Dual/Single Link TMDS

Quote:
Originally Posted by plesch
I used sed 's/critical_info//g' to sanitize bug reports. They contain all sorts of stuff.
Yeah, maybe it would be good if nvidia add an option to the bugreport script so that it omits things like a plain dmesg output or an entire hardware inventory.

It could be that some special cases are harder to debug and private exchange of information would be required, but I (like others) hesitate to post a bug report as it is now in a public forum on Internet.
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Old 07-10-07, 11:17 AM   #7
netllama
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Default Re: Dual/Single Link TMDS

I'm not really clear on what the issue is. Can someone explain which bug report contents are considered objectionable and why?
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Old 07-10-07, 11:57 AM   #8
pe1chl
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Default Re: Dual/Single Link TMDS

Especially the dmesg output can contain *lots* of information!!
For example, on my system (which has an ISDN card) it contains a list of all recent phonecalls I made with their source and destination phone number.
There is also a lot of information about the filesystems, disks etc.
Not really things that I want to publish far and wide. Maybe you should do an (e)grep on the dmesg output to get only what is interesting, like on /var/log/messages.
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Old 07-10-07, 12:04 PM   #9
netllama
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Default Re: Dual/Single Link TMDS

The problem is that we do not know what is 'interesting' until we see the entire thing. Since nearly every system is unique (kernel version, hardware, configuration, etc), grepping for only specific information could easily leave out something that is important.

As for your ISDN card leaking information about phone calls into dmesg, that sounds like a problem with the ISDN driver.

I'm not sure that I understand how including information on filesystems & disks is a privacy or security risk.

Regardless, anyone is welcome to manually strip out any information that they deem too sensitive to post publicly.
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Old 07-10-07, 02:37 PM   #10
pe1chl
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Default Re: Dual/Single Link TMDS

Probably many of the information leaks could be classified as bugs or maybe they could be suppressed with some config option, but a local dmesg information leak is IMHO a bit different from posting it on a forum...

The phone number thing is probably the biggest privacy issue, but I also would not like to show everyone how my disk volumes are named, how much data I have on them, and what CD/DVD titles I have mounted recently.

I understand that it could be difficult to filter the correct info from dmesg (largely because of the ad-hoc method of logging in Linux, without clear subsystem ids).
Maybe a possibility would be to add a "terse" option to the bugreport script that only puts things like the installer log, X config, X logfile and the /proc files that belong to the videocard, which are of direct significance to the video subsystem, in the output file.
This would then omit things like the hardware inventory, modules list, dmesg etc or only include those lines from those via egrep -i "nvidia|video|agp|acpi" (for example).
In cases where this is insufficient you could always ask for a complete report via mail.
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Old 07-10-07, 02:41 PM   #11
AaronP
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Default Re: Dual/Single Link TMDS

As an addendum to what Lonni said, if you do feel the need to edit a bug report, please make it obvious where the edits were so nobody gets confused and thinks your system is broken.
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Old 07-10-07, 03:35 PM   #12
netllama
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Default Re: Dual/Single Link TMDS

pe1chl,
Everyone's concept of privacy differs, and it would be impossible to strip out sufficient information from the bug report to everyone's liking and still make it useful to NVIDIA staff.

I'll note that I've had sporadic reports from people who felt that providing an nvidia-bug-report.log at all is a violation of their privacy.

The best solution here is to manually edit a bug report if you feel that its including information that you'd rather not have exposed (or email linux-bugs@nvidia.com if you'd prefer not to post it publicly on the forum). Per Aaron's recommendation, please note if you've manually edited the bug report so that everyone will be aware of the potential for missing information.

thanks,
Lonni
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