Output of this tool is useful for getting register value or debugging GPU hang.

Steps:

1. enable debugfs in kernel:
Kernel hacking --> Debug file system(CONFIG_DEBUG_FS=y).
(it's already enabled by default in some distributions)
Boot to the new kernel if needed.
Note: kernel version >=2.6.30-rc2 is required.

2. mount debugfs as root:
$ mount -t debugfs debugfs /sys/kernel/debug

3. download intel-gpu-tools:
e.g. the release under http://xorg.freedesktop.org/archive/individual/app/ or the latest code at git://anongit.freedesktop.org/git/xorg/app/intel-gpu-tools.
Install it by standard procedure: autogen.sh, configure, make, and make install.

4. reproduce the gpu hangs, then run as root to dump:
$ intel_gpu_dump > intel_gpu_dump.txt

5. file bug report with intel_gpu_dump.txt (or zipped if it's too big) attached.