The backlight is almost always powered external, not by the display controller. Generally the connections are "anode" and "cathode", ie directly on to the LED chains.
Unfortunately debugging displays is generally a lot of looking at black screens and guessing what might be wrong. Information from vendors is frequently incorrect.
In one case we resorted to taking the HDMI to MIPI bridge board that the vendor also sold, and decoding the MIPI signals that it used to initialise the display. That only vaguely matched the data we'd been given, but replicate that in the kernel driver and it worked fine. Decoding MIPI LP comms is relatively simple (it only uses data lane 0 and at a few 10's MHz), and if you're lucky your scope may have an option for decoding it.
Unfortunately debugging displays is generally a lot of looking at black screens and guessing what might be wrong. Information from vendors is frequently incorrect.
In one case we resorted to taking the HDMI to MIPI bridge board that the vendor also sold, and decoding the MIPI signals that it used to initialise the display. That only vaguely matched the data we'd been given, but replicate that in the kernel driver and it worked fine. Decoding MIPI LP comms is relatively simple (it only uses data lane 0 and at a few 10's MHz), and if you're lucky your scope may have an option for decoding it.
Statistics: Posted by 6by9 — Mon Jul 22, 2024 1:45 pm