BBB uarts & pps dts definitions

[Tony Hain]

Hi,

First, thanks to all that have worked on getting FreeBSD on ARM. I tried it
on a Rpi B awhile back, and gave up due to lack of time to work it through.
I now have 11 running on a BBB with poudriere/Qemu cross-compiled ports, and
also built NTPsec for it. The problem is figuring out the DTS mess.

I am not getting the PPS signal on P8-7 as per Ian's note about /dev/dmtpps:
https://lists.freebsd.org/pipermail/freebsd-arm/2015-August/012077.html 
I seriously suspect that is due to the default DTS, as gpioctl -lv only
shows pins 0-31, and the scope shows P8-7 is pulling the signal to ground
when I plug into the pin, suggesting it is in output mode. 
While the thread at:
https://forums.freebsd.org/threads/56920/
suggests there is a way to expand to the full set of gpio pins, I couldn't
figure out how from the references there.  I would guess there needs to be
another pinmux@ besides the one @800, but there is nothing I can find that
suggests what that should be.

I tried to use Gonzo's Overlay method referenced at:
https://kernelnomicon.org/?p=498
but the dtc version in /usr/bin doesn't support the -@ option to deal with
unreferenced variables as suggested by Adafruit and Rpi sites for Linux
builds. I don't see dtc in the ports tree, so short of chasing down the
current linux version and trying to port that, I am stuck with embedding
everything in the primary dts.

I figured it would be simpler to start debugging with the serial port first
since there was an example for the working console port. My original intent
was to use uart5 since it was also on P8, but given gpioctl is only listing
the first 32 I switched to uart1  (P9-26). Simply changing the "disabled" to
"okay" for the uart was sufficient to make it show up as /dev/ttyu1, but not
enough to make it work. Taking hints from various dts files for uart1, I
have:
      uart1_pins:  pinmux_uart1_pins {
                pinctrl-single,pins = <0x180 0x020 0x184 0x0>;
                 linux,phandle = <0x1>;
                 phandle = <0x1>;
        };
...
                serial at 48022000 {
                        compatible = "ti,am3352-uart", "ti,omap3-uart";
                        ti,hwmods = "uart2";
                        clock-frequency = <0x2dc6c00>;
                        reg = <0x48022000 0x2000>;
                        interrupts = <0x49>;
//                    status = "disabled";
                        status = "okay";
                        dmas = <0x29 0x1c 0x0 0x29 0x1d 0x0>;
                        dma-names = "tx", "rx";

                        pinctrl-names = "default";
                        pinctrl-0 = <&uart1_pins>;
                };
I am getting a duplication error for the phandle lines. I realize the
existing devices have unique hex values for those, but the only references
search is turning up and downloadable dtb files I can find have the phandle
for that uart as 0x1. Is there a reason that all the uarts are not listed
with the correct values & commented out in the default DTS? In addition,
uart4 & 5 don't have the dma lines that the others have ...  and those lines
don't appear in the reference linux dts files so I can't tell what they are
for. Comments in the dts hinting at where to look for references for other
values would make it easier to clone a working device for another one. 

Is there a plan to have a wiki for the dts/dtb/dtbo mechanism as implemented
for FreeBSD? 

Finally, adding beaglebone-green to my dts will be simple enough when I get
ready to put FreeBSD on that, but that should be part of the stock dts since
the hdmi itself is already marked as disabled in this dts, and removal of
that hardware is the primary difference between black & green as I
understand it. 

Tony