[PATCH 0/3] drm/bridge: Add Lontium LT8711UXD DP-to-HDMI transparent bridge

[Dennis Gilmore]

The Lontium LT8711UXD supports two modes of operation: autonomous mode,
where it configures itself via strapping resistors, and I2C-controlled
mode. Review of the earlier Orange Pi 5 Pro series raised the question
of how a future board requiring I2C control should be handled, a second
compatible with a driver or we make both work with a single compatible

This patch set covers autonomous mode only. On the Orange Pi 5 Pro,
resistors R9, R17, and R27 are unpopulated, which straps MODE_SEL low
leaving the device invisible on the I2C bus; I2C control is not enabled
on this board.

The earlier review thread is at:
https://lore.kernel.org/linux-devicetree/20260425031011.2529364-4-dennis@ausil.us/

One non-obvious detail in the DTS patch: vcc3v3_dp carries
regulator-always-on because simple-bridge only fires pre_enable once a
modeset starts, but no modeset will start until the connector reports
connected, and the connector won't report connected until HPD asserts,
and HPD won't assert until the bridge is powered. Holding the enable
line high from boot breaks this deadlock.

Tested on Orange Pi 5 Pro with Linux 7.0: HPD asserts, EDID reads,
link trains, and scanout reaches the display.

Please take a look.

Thank you,

Dennis Gilmore

Dennis Gilmore (3):
  dt-bindings: display: bridge: simple: document the Lontium LT8711UXD
    DP-to-HDMI bridge
  drm/bridge: simple: Add the Lontium LT8711UXD DP-to-HDMI bridge
  arm64: dts: rockchip: orangepi-5-pro: Add LT8711UXD DP-to-HDMI bridge

 .../display/bridge/simple-bridge.yaml         |  1 +
 .../dts/rockchip/rk3588s-orangepi-5-pro.dts   | 88 ++++++++++++++++++-
 drivers/gpu/drm/bridge/simple-bridge.c        |  5 ++
 3 files changed, 91 insertions(+), 3 deletions(-)

-- 
2.54.0