The other side of the moon

I've been using a GeForce MX 2 for well over a year. It worked quite well with RH8, FC1 and Knoppix. I needed to use the proprietary drivers provided by Nvidia to get hardware acceleration though.

Motherboard: ASUS A7N266

A couple of months ago, upgraded to FC2, and the nvidia driver wouldn't work anymore. I had to run back to Bangalore, and since no one at home really needed hardware acceleration, I switched back to the free nv driver from X (well, I was using x.org now).

This December... well, yesterday actually, I decided to try out 3ddesktop, but of course, this requires hardware acceleration. So I started. Went through a lot to get it to work, and the details are boring. However, what I learnt could help others, so I'll document that.

The problem:

When starting X with the nvidia driver, the screen blanked out and the system froze. Pushing the reset button is the only thing that worked.

Solutions and Caveats:

Get the latest NVIDIA drivers and try.

At the time of writing, the latest drivers from the nvidia site are in the 1.0-6629 package. This doesn't work with the GeForce MX 2, and many other older chips, so if you try to use it, you'll spend too much time breaking your head for nothing. Instead, go for the 1.0-6111 driver, which does work well...

On kernels below 2.6.5 that is. FC2 ships with a modified 2.6.5 kernel that has a forced 4K stack and CONFIG_REGPARM turned on. The NVIDIA drivers are (or were) compiled with 8K stacks and do not work with CONFIG_REGPARM turned on. I'd faced similar problems when I first used the nvidia driver, and recompiling my kernel with 8K stacks fixed the problem.

Searching the net, I came across dozens of articles that spoke about 4K stacks v/s 8K stacks in the 2.6 kernel, but also said that from 5xxx onwards, the nvidia driver supported 4K stacks and CONFIG_REGPARM.

I tried getting prebuilt kernels (smaller download) with 16K stacks, but it didn't help, so finally decided to downlad the entire 32MB kernel source for 2.6.10.

While compiling, I came across this thread on NV News (pretty much the best resource for nvidia issues on linux). In short, the 6111 driver wouldn't work with kernels above 2.6.5 or something like that. I needed to patch the kernel source.

The patch was tiny enough: in arch/i386/mm/init.c, add a single line:
EXPORT_SYMBOL(__VMALLOC_RESERVE);
after the __VMALLOC_RESERVE definition.

Stopped compilation, made the change and restarted compilation.

Also had to rebuild the NVIDIA driver package, again as documented in that thread:

- extract the sources with the command : ./NVIDIA-Linux-x86-1.0-6111-pkg1.run --extract-only
- in the file "./NVIDIA-Linux-x86-1.0-611-pkg1/usr/src/nv/nv.c" replace the 4 occurences of
'pci_find_class' by 'pci_get_class'
- repack the nvidia installer with the following command:

sh ./NVIDIA-Linux-x86-1.0-6111-pkg1/usr/bin/makeself.sh --target-os Linux --target-arch x86 NVIDIA-Linux-x86-1.0-6111-pkg1 NVIDIA-Linux-x86-1.0-6111-pkg2.run "NVIDIA Acclerated Graphics Driver for Linux-x86 1.0-6111" ./nvidia-installer

The new installer is called "NVIDIA-Linux-x86-1.0-6111-pkg2.run"

With these changes, the driver compiled successfully and I was able to insert it.

I had a minor problem when rebooting. usbdevfs has become usbfs, so a change has to be made in /etc/rc.sysinit. Change all occurences of "usbdevfs usbdevfs" to "usbfs none".

Once you've done this, X should start with acceleration on.

3ddesktop is slow, but it starts up. Tux racer works well.

What I think is really cool about this solution, is that I did not have to make a single post to a single mailing list or forum. All the information I needed was already on the net. It was just a matter of reading it, understanding what it said, and following those instructions. For example, there were many threads on screen blanking with the 6629 driver, and somewhere in there was mentioned that the new driver didn't support older hardware, but that the 6111 did. That was the key that brought me the solution. I knew the 6111 didn't work out of the box, because I'd already tried it, but now I could concentrate on threads about the 6111 exclusively, only looking for anything that sounded familiar.