Android boot animation not showing on primary display

[dennis3]

When I upgraded from Android 11 2.2.0 to 2.6.0, Our primary display no longer shows the Android boot animation during startup (the display is left blank).  We have a Vendor evaluation board with an LVDS display and that works fine.  Our device uses a MIPI DSI display.

I know the boot animation is starting and playing as before.  You can see the status of the boot animation in logcat and it looks normal.  In addition, if I connect to the device during boot over adb, I can use a service like Vysor or scrcpy to see the screen and the boot animation is playing there fine.  As soon as the boot sequence is complete, and Android starts, our primary display begins to show the expected content.

Any ideas why our display fails to show anything during the boot animation?  I'm unsure why this would work fine for the LVDS display but not for our custom mipi display (all else being pretty much the same except for the DTS file for different boards).  Ideas for debugging appreciated, thanks.

[dennis3 · Accepted solution]

The problem turned out to be a missing kernel config option.
CONFIG_ION_UNMAPPED_HEAP=y
was requried to show the boot animation and for some reason was not being set in our config.

[Rita_Wang]

Which board are you using? For your customer mipi display have you finished porting software to it? Can it work well alone?

[dennis3]

Thank you @Rita_Wang ,

We our using our own custom daughter board but we use the Variscite imx8m plus main board. Yes, the display driver is ported fully (as far as I know maybe I'm missing something). 

You can see during boot, the messages that display is starting, e.g., panel_prepare, panel_enable etc.  This is the same for both 11 2.2.0 and 11 2.6.0, however on 2.6.0, after the enable the screen stays blank. After the boot animation when the device says "<device> is starting", the display finally enables and works normally.