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Playbook: display

scope: generic · severity: technique · confidence: proven · subsystem: display

Goal: the panel lights and holds a stable image.

Done when: a frame reaches the panel and survives a suspend/resume cycle.

Order

Section: Order
  1. Panel identification. Get the vendor DSI init sequence: from the downstream kernel’s panel driver, from a dsi-panel-*.dtsi, or from the stock boot image. This is the single highest-value artefact — an init sequence you can transcribe beats any amount of guessing.
  2. DSI host before panel. Confirm the DSI controller and PHY come up before blaming the panel driver.
  3. Compression. If the panel uses DSC, the parameters must match exactly. A DSC mismatch produces a lit-but-garbled panel, which reads as a timing problem and is not.
  4. Then the compositor. Only once a frame is provably reaching the panel.

The traps

Section: The traps
  • Until this playbook is done, never-judge-a-boot-by-the-screen governs every other playbook. Flip PORTHOLE_PANEL_STAYS_DARK=0 in the profile when it is done — that is a real milestone.
  • A panel that lights at the bootloader’s timings and dies at yours means the bootloader left it initialised. Prove your init sequence runs from a cold panel.