Created attachment 134797 [details]
journalctl of affected kernel

Kernel: kernel-PAE-core-4.13.4-200.fc26.i686
Machine: Acer Aspire One ZG5
Video outputs: one LCD display 1024x600, one VGA port with no monitor attached.

00:02.0 VGA compatible controller: Intel Corporation Mobile 945GSE Express Integrated Graphics Controller (rev 03) (prog-if 00 [VGA controller])
	Subsystem: Acer Incorporated [ALI] Device 015b
	Flags: bus master, fast devsel, latency 0, IRQ 16
	Memory at 58480000 (32-bit, non-prefetchable) [size=512K]
	I/O ports at 60c0 [size=8]
	Memory at 40000000 (32-bit, prefetchable) [size=256M]
	Memory at 58500000 (32-bit, non-prefetchable) [size=256K]
	[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: i915
	Kernel modules: i915

This is the same machine affected in bug https://bugs.freedesktop.org/show_bug.cgi?id=98930 .

After updating to distro kernel 4.13.4 or 4.13.5, and rebooting, boot is normal until KMS takes over, then the display on the LCD gets garbled in a square area (800x800) at the left of the screen. The garbled area persists during the rest of the startup and into the login screen and makes the display unusable.

Previous kernel kernel-PAE-4.12.14-300.fc26.i686 does not garble the display, although it still shows a backtrace as described in #98930, as this is the exact same machine.

Version-Release number of selected component (if applicable):
kernel-PAE-4.13.4-200.fc26.i686

How reproducible:
Always

Steps to Reproduce:
1. Acer Aspire One ZG5 32-bit with Fedora 26 and kernel-PAE-4.13.4-200.fc26.i686
2. Boot with updated kernel
3.

Actual results:
Garbled screen in a square section when KMS takes over.

Expected results:
No screen corruption.

Additional info:
Using journalctl I have captured a dmesg output of the affected kernel. Look for the string "plane B assertion failure, should be off on pipe B but is still active".