[Intel-gfx] [PATCH v5 00/12] Enable GPU switching on pre-retina MacBook Pro

Lukas Wunner lukas at wunner.de
Mon Jan 11 11:09:20 PST 2016

Enable GPU switching on the pre-retina MacBook Pro (2008 - 2013), v5.

The main obstacle on these machines is that the panel mode in VBIOS
is bogus. Fortunately gmux can switch DDC independently from the
display, thereby allowing the inactive GPU to probe the panel's EDID.

In short, vga_switcheroo and apple-gmux are amended with hooks to
switch DDC, DRM core is amended with a drm_get_edid_switcheroo() helper,
and relevant drivers are amended to call that for LVDS outputs.

The retina MacBook Pro (2012 - present) uses eDP and cannot switch
AUX independently from the main link. The main obstacle there is link
training, I'm currently working on this, it will be addressed in a
future patch set.

This series is also reviewable on GitHub:


* New patch [01/12]: vga_switcheroo handler flags
  Alex Deucher asked if this series might regress on non-Apple laptops.
  To address this concern, I let handlers declare their capabilities in
  a bitmask. DRM drivers call drm_get_edid_switcheroo() only if the
  handler has set the VGA_SWITCHEROO_CAN_SWITCH_DDC flag.
  Currently just one other flag is defined which is used on retinas.

* Changed patch [02/12]: vga_switcheroo DDC locking
  Rename ddc_lock to mux_hw_lock, suggested by Daniel Vetter.

* New patch [03/12]: track switch state of apple-gmux
  Fixes a bug in previous versions of this series which occurred if
  the system was suspended while DDC was temporarily switched:
  On resume DDC was switched to the wrong GPU.

* New patches [09/12 - 12/12]: deferred probing
  Previously I used connector reprobing if the inactive GPU's driver
  loaded before gmux. I've ditched that in favor of deferred driver
  probing, which is much simpler. Thanks to Daniel Vetter for the

Caution: Patch [09/12] depends on a new acpi_dev_present() API which
will land in 4.5 via Rafael J. Wysocki's tree.

I would particularly be interested in feedback on the handler flags
patch [01/12]. I'm not 100% happy with the number of characters
required to query the flags (e.g.: if (vga_switcheroo_handler_flags() &
VGA_SWITCHEROO_CAN_SWITCH_DDC)), but failed to come up with something
shorter. Thierry Reding used a struct of bools instead of a bitmask
for his recent drm_dp_link_caps patches. Maybe use that instead?



Lukas Wunner (12):
  vga_switcheroo: Add handler flags infrastructure
  vga_switcheroo: Add support for switching only the DDC
  apple-gmux: Track switch state
  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
  apple-gmux: Add helper for presence detect
  drm/i915: Defer probe if gmux is present but its driver isn't
  drm/nouveau: Defer probe if gmux is present but its driver isn't
  drm/radeon: Defer probe if gmux is present but its driver isn't

 Documentation/DocBook/gpu.tmpl                   |   5 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_atpx_handler.c |   3 +-
 drivers/gpu/drm/drm_edid.c                       |  26 +++++
 drivers/gpu/drm/i915/i915_drv.c                  |  12 +++
 drivers/gpu/drm/i915/intel_lvds.c                |   8 +-
 drivers/gpu/drm/nouveau/nouveau_acpi.c           |   2 +-
 drivers/gpu/drm/nouveau/nouveau_connector.c      |  21 +++-
 drivers/gpu/drm/nouveau/nouveau_drm.c            |  11 +++
 drivers/gpu/drm/radeon/radeon_atpx_handler.c     |   3 +-
 drivers/gpu/drm/radeon/radeon_connectors.c       |   6 ++
 drivers/gpu/drm/radeon/radeon_drv.c              |  11 +++
 drivers/gpu/vga/vga_switcheroo.c                 | 119 ++++++++++++++++++++++-
 drivers/platform/x86/apple-gmux.c                | 111 ++++++++++++++++-----
 include/drm/drm_crtc.h                           |   2 +
 include/linux/apple-gmux.h                       |  39 ++++++++
 include/linux/vga_switcheroo.h                   |  36 ++++++-
 16 files changed, 382 insertions(+), 33 deletions(-)
 create mode 100644 include/linux/apple-gmux.h

-- (Apple Git-48)

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