There are two email threads between Chris Wilson and me:

https://www.mail-archive.com/xorg-devel@lists.x.org/msg43152.html

This lead to the 3 patches:

commit 9f7c1a4c4f2a6352263c36e75a984ed4095adbc0
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Sep 25 16:29:14 2014 +0100

    sna: Check for scanout pitch restrictions on linear GPU bo

commit e9087f50bf6dafff87c566d3bdbe6cef29d71fde
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Sep 25 16:41:11 2014 +0100

    sna: Check scanout Pixmaps are the correct pitch and convert if necessary

commit f785035d5bd42a778d4be0bf3ff8678bd7a7e503
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Sep 26 21:01:43 2014 +0100

    sna: Allow move-to-gpu to fail during ScreenCreateResources

Backport these patches to 13.2.