Add a display driver for the MT8183 kukui family of ChromeOS devices
(e.g. the Lenovo IdeaPad Duet, google,krane), where the display
pipeline is already initialized and running when the payload is
handed off by depthcharge. depthcharge's display_cleanup() stops the
overlay engines and turns the backlight off before the jump, so the
driver only revives the pipeline: it re-enables the OVL0 engines
(OVL_EN @ +0x000c and OVL0_2L_EN @ +0x100c, offsets from depthcharge's
device-era mtk_ddp.c), drives the backlight GPIOs high (DISP_PWM,
pin 43, and EN_LCD_BL, pin 176, through the GPIO controller dout block
at 0x10005000+0x100), and renders the console into the live scanout
surface.
The geometry comes from the coreboot table framebuffer record, which
sits at the fixed kukui address 0xffed9000; when its physical_address
is 0 (what upstream coreboot 4.14 publishes on kukui), the live
scanout address is taken from the OVL layer 0 address register
(+0x0f40), which the firmware leaves in place across the handoff.
The driver binds to the existing ovl0 device tree node
(mediatek,mt8183-disp-ovl) and requires no display initialization.
vhaudiquet
f0470c9be5