VT switching (to frecon) doesn't work on Samus.

Steps:
(0) Disable PSR (see note [1] at the end)
(1) emerge-samus --unmerge chromeos-kernel-3_14
(2) USE="-kernel-3_14 kernel-4_4" emerge-samus linux-sources
(3) ./update_kernel ...
(4) Try CTRL+ALT+F2 to get to frecon/VT2

What happens:

We don't switch over to VT2. Kernel/syslong logs this instead:

[   15.656512] frecon: trying /dev/dri/card0
[   15.659987] frecon: Frecon using drm driver i915, version 1.6, date(20151010), desc(Intel Graphics)
[   15.671180] DEBUG: tsm_screen: new screen
[   15.674280] DEBUG: tsm_vte: new vte object
[   15.682998] frecon: drmSetMaster failed: Invalid argument
[   15.687550] frecon: Unable to set crtc: Permission denied
[   15.700617] frecon: drmSetMaster failed: Invalid argument
[   15.705465] frecon: Unable to set crtc: Permission denied
[   15.959840] frecon: drmSetMaster failed: Invalid argument
[   15.964090] frecon: Unable to set crtc: Permission denied


I think I traced down the issue to around this commit:

commit c996fd0b956450563454e7ccc97a82ca31f9d043
Author: Thomas Hellstrom <thellstrom@vmware.com>
Date:   Tue Feb 25 19:57:44 2014 +0100

    drm: Protect the master management with a drm_device::master_mutex v3


I was able to get switch-to-VT2 working by reverting a piece of that (see attached patch), but then I can't get back to VT1 properly.

[1] https://groups.google.com/a/google.com/forum/#!topic/chromeos-kernel-rebase/WC2fUGH8w5s
 

Deleted: 4.4-vt-switch.patch 460 bytes

4.4-vt-switch.patch 460 bytes Download