Re: Serial UART on RPi3

[Dustin Marquess <dmarquess%gmail.com@localhost>]

On Sat, Dec 22, 2018 at 2:29 PM Jason Thorpe <thorpej%me.com@localhost> wrote:
>
> > 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.

Ah, that helps, thanks.  I was using the images from
http://www.invisible.ca/arm/ .  I just did a refresh rebuild of
current and indeed the .dtb files match now.

-Dustin