[PATCH v4 0/6] Enable gpu switching on the MacBook Pro

[Lukas Wunner]

Changes since v3:
  * Previously when switching the display, the DDC lines were switched
    as well. But actually this is not necessary: If a GPU probes EDID,
    DDC must be switched and locked to the GPU anyway, so why switch
    DDC preemptively? Also, previously the DDC lines were switched back
    to the previous owner on unlock. This is unnecessary for the same
    reason. So I did away with all that and it simplifies the code
    considerably. This works fine as long as anything accessing DDC
    calls vga_switcheroo_lock_ddc() first. If something in the kernel
    or a VM or in user space accesses DDC and omits locking it first,
    things may go awry. (However, if locking is omitted, things could
    go awry with the previous behaviour as well.) I'm curious if this
    new behaviour provokes objections.
  * I now have conclusive evidence that only the pre-retina MacBook Pro
    can switch DDC. The mux in the retina is incapable of that. So the
    ->switch_ddc callback is no longer advertised to vga_switcheroo
    on retinas.


Also available on GitHub for easier reviewing:
https://github.com/l1k/linux/commits/mbp_switcheroo_v4


For those who haven't been following this series so far:

The pre-retina MacBook Pro uses an LVDS panel and a gmux controller
to switch the panel between its two GPUs. The panel mode in VBIOS
is notoriously bogus on these machines and some models have no
VBIOS at all, so the inactive GPU cannot set up its LVDS output.

Extend vga_switcheroo to support switching only the DDC lines.
Introduce a drm_get_edid_switcheroo() helper which uses this feature.
Amend i915, nouveau and radeon to call it for LVDS connectors.

This only enables EDID probing on the pre-retina MBP (2008 - 2013),
and only under the condition that apple-gmux loads before the DRM
drivers. Later patches will address reprobing of the DRM drivers
if apple-gmux loads late.

The retina MBP (2012 - present) uses eDP and is apparently not
capable of switching AUX separately from the main link.
This will also be addressed in later patches.


Previous installments:
v1: http://lists.freedesktop.org/archives/dri-devel/2015-April/081515.html
v2: http://lists.freedesktop.org/archives/dri-devel/2015-August/088156.html
v3: http://lists.freedesktop.org/archives/dri-devel/2015-October/091741.html


Lukas Wunner (6):
  vga_switcheroo: Add support for switching only the DDC
  apple-gmux: Add switch_ddc support
  drm/edid: Switch DDC when reading the EDID
  drm/i915: Switch DDC when reading the EDID
  drm/nouveau: Switch DDC when reading the EDID
  drm/radeon: Switch DDC when reading the EDID

 drivers/gpu/drm/drm_edid.c                  | 26 ++++++++++++
 drivers/gpu/drm/i915/intel_lvds.c           |  3 +-
 drivers/gpu/drm/nouveau/nouveau_connector.c | 13 +++++-
 drivers/gpu/drm/radeon/radeon_connectors.c  |  4 ++
 drivers/gpu/vga/vga_switcheroo.c            | 66 ++++++++++++++++++++++++++++-
 drivers/platform/x86/apple-gmux.c           | 21 ++++++++-
 include/drm/drm_crtc.h                      |  2 +
 include/linux/vga_switcheroo.h              | 15 +++++--
 8 files changed, 141 insertions(+), 9 deletions(-)

-- 
1.8.5.2 (Apple Git-48)