Re: Serial UART on RPi3

[Jason Thorpe <thorpej%me.com@localhost>]

> On Dec 22, 2018, at 11:14 AM, Dustin Marquess <dmarquess%gmail.com@localhost> wrote:
> 
> 2) I have a feeling that the system is using the default of mapping
> GPIO 14/15 to the BCM AUX UART instead of the ARM PL011 UART.  Since
> overlays don't seem to work, do I need to modify
> /boot/bcm2837-rpi-3-b.dtb to accomplish this? I'm assuming so.  If so,
> that part I've done before.

You are having the same overlay problem I was having.  It's likely the .dtb files on your image were not built correctly.  At least in -current, the ones build when you compile a kernel are built with -@ option passed to dtc, which provides the necessary symbol table in the .dtb file or the Broadcom loader to process the overlay.

You can confirm this by running "dtc -O dts /boot/bcm2837-rpi-3-b.dtb" and looking for the symbol table (I guess it should be near the end of the output).

Try copying the .dtb files from the kernel compile directory when you built your kernel into /boot.

-- thorpej