[PATCH v2 0/3] drm/amd: Enable 2x1 tiled display support on Apple 5K iMacs

[Richard Lane <richardlanedev@gmail.com>]

Hi folks,

Apple 27" 5K iMacs (2014-2019, iMac15,1 through Polaris-based iMac19,1)
drive their internal 5120x2880 panel as a 2x1 tiled display using two
2560x2880 streams over an internal eDP root link and a secondary DP
link.

At boot, the Apple EFI firmware initializes only a single 2560x2880 pipe
and leaves the secondary DP tile unlatched with HPD deasserted. Because
the secondary tile reports HPD low and requires a vendor-specific DPCD
handshake before it responds as a DisplayPort sink, amdgpu currently
fails to detect the second tile, leaving Linux limited to single-tile
resolutions.

This series enables full 5120x2880 dual-tile operation on DCE < 12 Apple
5K iMacs so that the internal 5K panel behaves like a standard DisplayID
tiled monitor:

1. Calculate the pre-OS framebuffer reservation in GMC v7 and v8 using
   mmGRPH_PITCH and the mmGRPH_PRIMARY_SURFACE_ADDRESS offset from
   vram_start so the full [3 MiB, 59.25 MiB) Apple EFI scanout surface
   is preserved during boot handover without vendor-specific quirks.
2. Point the secondary DP link to the root eDP link via an EDID quirk on
   DCE < 12 (covering iMac15,1, iMac17,1, iMac18,3, and Polaris-based
   iMac19,1), latch the secondary tile via DPCD 0x4F1 on the root eDP
   link, write the 3-byte Boot Camp source table (0x310) on the
   secondary link, keep the secondary tile out of D3 power-down, and
   unlatch the TCON back to single-pipe mode on suspend/shutdown. Once
   unlocked, DRM's DisplayID parser populates has_tile, tile_group, and
   tile_is_single_monitor on both connectors natively. (DCE >= 12
   support for Vega-equipped iMac19,1, iMacPro1,1, and 2020 iMac20,x is
   noted as TODO.)
3. Report all_displays_in_sync = true to PowerPlay after
   dc_commit_streams() whenever all active streams are synchronized into
   a single timing group by program_timing_sync()
   (timing_sync_info.group_size == params.stream_count), allowing SMU7
   to downclock MCLK at idle without modeset underflows.

Changes in v2:
- Patch 1: Replaced the hardcoded 64 MiB Apple quirk in amdgpu_gmc.c
  with a generic calculation in gmc_v7_0_get_vbios_fb_size() and
  gmc_v8_0_get_vbios_fb_size() using mmGRPH_PITCH and
  mmGRPH_PRIMARY_SURFACE_ADDRESS.
- Patch 2: Dropped the DRM_MODE_CONNECTOR_eDP override in
  amdgpu_dm_connector.c in favor of DRM's native DisplayID tile
  properties (has_tile, tile_group, tile_is_single_monitor).
  Renamed tiled_peer to apple_5k_peer and set it only on the secondary
  DP link, removing dm_helpers_wire_tiled_peer(),
  dc_link_is_apple_5k_secondary(), and inline explanatory comments.
- Patch 3: Made the PowerPlay sync check generic for any combination of
  synchronized displays by checking timing_sync_info.group_size ==
  params.stream_count instead of tiled_peer.

Regards,
Richard

Richard Lane (3):
  drm/amdgpu: use pitch and surface offset for GMC v7/v8 fb size
  drm/amd/display: unlock secondary tile on Apple 5K iMac panels
  drm/amd/display: report synced displays to PowerPlay for MCLK switch

 drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c         |  8 +++--
 drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c         |  8 +++--
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 29 +++++++++++++++++++
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 22 ++++++++++++++
 drivers/gpu/drm/amd/display/dc/dc.h           |  1 +
 .../drm/amd/display/dc/link/link_detection.c  |  7 ++++-
 .../dc/link/protocols/link_dp_capability.c    |  4 +++
 .../display/dc/link/protocols/link_dp_phy.c   |  3 ++
 8 files changed, 75 insertions(+), 7 deletions(-)

-- 
2.55.0