[GeForce 9400M] External monitor blanks when reaching lowest power state

[bardo]

Hi all,
I'm experiencing a blanking problem which I didn't find referenced anywhere, looking for help

Hardware

• laptop: MacBook 5,1 (late 2008, aluminium, non-Pro, no audio support over DisplayPort)
• video card: GeForce 9400M using the DisplayPort output
• cabling: DisplayPort→HDMI adapter
• external monitor: Samsung SyncMaster P2370HD

Software

• distro: Arch Linux x86_64 (fully updated to [testing] repo)
• kernel: Linux 3.1.4 (distro-packaged)
• driver version: 290.10
• xorg server version: 1.11.2
• desktop environment: Gnome 3

Kernel

[bardo@antani ~]$ uname -a
Linux antani 3.1.4-1-ARCH #1 SMP PREEMPT Tue Nov 29 08:55:45 CET 2011 x86_64 Intel(R) Core(TM)2 Duo CPU P8600 @ 2.40GHz GenuineIntel GNU/Linux

Xorg configuration

Section "Device"
	Identifier "Nvidia 9400M"
	Driver "nvidia"
	VendorName "NVIDIA Corporation"
	Option "NoLogo" "1"
	#Option "ConnectedMonitor" "DFP"
	Option "TripleBuffer" "1"
	Option "DPMS" "1"
	Option "RegistryDwords" "PerfLevelSrc=0x3333"
	Option "Coolbits" "1"
	Option "OnDemandVBlankInterrupts" "1"
	Option "RandRRotation" "true"
	Option "RegistryDwords" "EnableBrightnessControl=1"
EndSection

Using the nvidia-settings application, with powermizer set to adaptive mode, I noticed that every time the frequency drops to the minimum (100MHz) the external monitor loses signal. There are several workarounds (switching tty7→tty1→tty7, blindly launching an opengl app like glxgears, blindly launching nvidia-bug-report.sh...), but all do the same thing: raise the graphics clock frequency.

When running in maximum performance mode the problem doesn't (obviously) happen, but this is less than ideal on a laptop, especially one with not-so-great cooling like the MacBook.

Each time the external monitor "cycles" three lines get spit out in Xorg.0.log:

[288268.284] (II) Open ACPI successful (/var/run/acpid.socket)
[288268.288] (II) NVIDIA(0): Setting mode "DFP-1:nvidia-auto-select@1920x1080+0+0"
[288268.375] (--) synaptics: bcm5974: touchpad found

(The first one can be suppressed by stopping the acpid daemon, the second one seems to be the relevant one.)

The problem didn't show up when I used Xfce, so it's probably related to Gnome 3.

When I'm on the external monitor I disable the internal one.

It's hard to do some good debugging because I'm hit by the "invisible console" bug (as soon as the nvidia driver is loaded I can't see ttys anymore since the backlight turns off when switching to a real console).

Attached is the bug report log, which I ran while the screen was blank, but running it raised the clock frequency middle-way, so I don't know how much it can be trusted.

Right now I'd be happy to find any good workaround which doesn't involve the maximum performance mode. If there was a way to just disable the lowest frequency while keeping the adaptive mode it would be great while waiting for a real solution!


Thanks for getting to here