[Letux-kernel] [PATCH 00/20] A bunch of JZ4730 fixups for letux-kernel

[H. Nikolaus Schaller]

> Am 11.01.2021 um 16:27 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> A problem seems to be that ingenic_drm_encoder_atomic_check() has no formats.
> 
> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/ingenic/ingenic-drm-drv.c#L535
> 
> I think I remember this from the CI20 HDMI work but do not know the solution.

Just found something. In our case it should come from the panel_simple driver.
There is code to setup display_info.num_bus_formats:

https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/panel/panel-simple.c#L222

But it is set only if there is hard-coded, i.e. panel table indexed by compatible
string. But not if it is initialized purely from device tree.

So it looks as if some mechanism is missing to define the connector (type, bus formats)
in device tree... Or I am missing where and how it can be defined by DT.

BTW: hacking some desc->bus_format=MEDIA_BUS_FMT_RGB565_1X16; into this function
makes the jz4730 LCDC start up and enable backlight... But image is wrong and
leads to "vblank wait timed out". So there is now some initialization of the LCDC,
but it is wrong.

BR,
Nikolaus