[Bug 79038] [Regression][[i945] Crashes and bad performance on Lenovo X60 with coreboot and native graphics init

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=79038

--- Comment #2 from info at gluglug.org.uk ---
Created attachment 99547
  --> https://bugs.freedesktop.org/attachment.cgi?id=99547&action=edit
debugging results

Note, this bug report as listed in the main description is about a regression
in linux since 3.12 and beyond which causes graphical instability
(glitches/crashes)
on the ThinnkPad X60 and ThinkPad T60 when running "native graphics
initialization"
in coreboot, instead of Intel's proprietary Video BIOS or VBIOS ROM.

Before linux 3.12, no issues existed, the code worked (3D worked, no
instability).

Here I have some debugging results:
 - dmesg output
 - xorg log
 - kernel log
 - uname output

Distro: Trisquel 6 
http://trisquel.info/
--

linux-image-gnu-3.14.4-gnuowen_1_i386.deb
has 17fec8a (kernel git) as-is

linux-image-gnu-3e14-gnu-stolenmem-owen_1_i386.deb
has 17fec8a (kernel git) reverted

When booting with the one that has 17fec8a, gdm won't start desktop.
Restarting gdm makes desktop appear.

now see the debugging output in both directories below this one.

As per the bug report, these issues were not seen until regression
after kernel 3.12. As per above, there are two sets of debugging results:
 * with 17fec8a in kernel (as-is)
 * without (17fec8a reverted)

These kernels were shared with me, compiled for Trisquel 6.0 (distribution).
Link:
 * http://samnoble.org/thinkpad/kernel/linux-image-3.14.4-gnuowen_1_i386.deb
 *
http://samnoble.org/thinkpad/kernel/linux-image-3.14.4-gnu-stolenmem-owen_1_i386.deb
(the 2nd one reverts 17fec8a, which removes the issues introduced in 3.12+)

--

For both kernels, I am booting with "drm.debug=0x06" kernel parameter in GRUB.

I am using coreboot as per http://libreboot.org/howto.html#x60_native_notes

How to find the code to see how coreboot is initializing the GPU:

You can see the i915 init code at http://review.coreboot.org/#/c/5320
under (using that patch):
 * src/northbridge/intel/i945/gma.c
 * src/mainboard/lenovo/x60/devicetreee.cb

Those are modified in the patch. New files are added:
 * src/northbridge/intel/i945/chip.h

To get the full source, git clone coreboot with:
$ git clone http://review.coreboot.org/coreboot
$ git fetch http://review.coreboot.org/coreboot refs/changes/20/5320/6 && git
checkout FETCH_HEAD

And look at those files (patched) listed in the source, as per list at
http://review.coreboot.org/#/c/5320

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