Override DPCD information

skohrs · 10-12-11, 02:35 PM

Greetings,

I'm trying to solve a problem where a Quadro NVS 450 cannot determine the proper DisplayPort link rate, lane count, and pixel clock speed, when the monitors are turned off. Is there a way to override these parameters in the xorg.conf?

Here is a snippet from the Xorg log when the monitors are off:

Code:

(WW) Oct 11 15:39:28 NVIDIA(GPU-0): DFP-2: Failed to read DPCD
(II) Oct 11 15:39:28 NVIDIA(GPU-0):     Maximum link rate:   1.62 Gbps per lane
(II) Oct 11 15:39:28 NVIDIA(GPU-0):     Maximum lane count:  1
(II) Oct 11 15:39:28 NVIDIA(GPU-0):     Maximum pixel clock: 71.287 MHz

Here is a snippet from the Xorg log when the monitors are on:

Code:

(II) Oct 11 15:52:53 NVIDIA(GPU-0): DFP-2: DisplayPort revision 1.1
(II) Oct 11 15:52:53 NVIDIA(GPU-0):     Maximum link rate:   2.70 Gbps per lane
(II) Oct 11 15:52:53 NVIDIA(GPU-0):     Maximum lane count:  4
(II) Oct 11 15:52:53 NVIDIA(GPU-0):     Maximum pixel clock: 475.248 MHz

Thank you.

PS I'm receiving the following error while trying to upload a nvidia-bug-report:

nvidia-bug-report.log.gz:
Your file of 160.5 KB bytes exceeds the forum's limit of 146.9 KB for this filetype.

**AaronP** · 10-12-11, 03:21 PM

I'm afraid not, sorry. Is there any way you can make sure the monitors are on before trying to start X?

**AaronP** · 10-12-11, 04:09 PM

Actually, I take that back: there's a "NoDisplayPortBandwidthCheck" mode validation override. That completely ignores DisplayPort bandwidth constraints, but since your monitors negotiate the maximum bandwidth when they're on anyway, that shouldn't matter.

See ftp://download.nvidia.com/XFree86/Li...ModeValidation

skohrs · 10-12-11, 04:25 PM

Thanks for the information. I am using the "NoDisplayPortBandwidthCheck" mode validation override, but it computes the values way too low. Do you happen to know how those values are calculated or are they hardcoded somewhere?

**AaronP** · 10-17-11, 03:09 PM

I'm not sure what you mean. NoDisplayPortBandwidthCheck prevents the driver from considering the DisplayPort bandwidth when validating modes, so it should let through modes that would be valid otherwise and are only rejected because the DP device isn't responding.

10-12-11, 03:21 PM	#2
AaronP NVIDIA Corporation Join Date: Mar 2005 Posts: 2,487	Re: Override DPCD information I'm afraid not, sorry. Is there any way you can make sure the monitors are on before trying to start X?

10-12-11, 04:09 PM	#3
AaronP NVIDIA Corporation Join Date: Mar 2005 Posts: 2,487	Re: Override DPCD information Actually, I take that back: there's a "NoDisplayPortBandwidthCheck" mode validation override. That completely ignores DisplayPort bandwidth constraints, but since your monitors negotiate the maximum bandwidth when they're on anyway, that shouldn't matter. See ftp://download.nvidia.com/XFree86/Li...ModeValidation

10-12-11, 04:25 PM	#4
skohrs Registered User Join Date: Oct 2011 Posts: 2	Re: Override DPCD information Thanks for the information. I am using the "NoDisplayPortBandwidthCheck" mode validation override, but it computes the values way too low. Do you happen to know how those values are calculated or are they hardcoded somewhere?

10-17-11, 03:09 PM	#5
AaronP NVIDIA Corporation Join Date: Mar 2005 Posts: 2,487	Re: Override DPCD information I'm not sure what you mean. NoDisplayPortBandwidthCheck prevents the driver from considering the DisplayPort bandwidth when validating modes, so it should let through modes that would be valid otherwise and are only rejected because the DP device isn't responding.