[U-Boot] Raspberry Pi Compute Module 1 mini-UART

edrose edrose at outramresearch.co.uk
Fri Nov 29 16:34:56 UTC 2019


I've done some more digging, and have made a bit of progress (I think).

After fiddling with the device-tree, I've managed to get the serial port to
show up when running `dm tree`. I appended this block to the end of
bcm2835-rpi-b.dts:

&uart1 {
	pinctrl-names = "default";
	pinctrl-0 = <&uart1_gpio40>;
	status = "okay";
};

And the relevant output of `dm tree is:

Class    index  Probed  Driver      Name                                       
-----------------------------------------    
                          ...
pinconfig   32  [ + ]   pinconfig   |   |   |-- uart0_gpio14
                          ...
pinconfig   42  [   ]   pinconfig   |   |   |-- uart1_gpio40
                          ...
serial      0  [ + ]   bcm283x_pl  |   |-- serial at 7e201000                     
serial      1  [   ]   serial_bcm  |   |-- serial at 7e215040                     

So that indicates that it sees the serial port, knows which driver to use,
and has the correct address. However it has not probed the device, nor has
it probed the pinconfig that MUXes it to the pin I've set in the dts file.

It also appears to have an index , however specifying CONFIG_CONS_INDEX
doesn't change the port that is used, nor does it change the output of
`dm-tree`.

So I'm still a bit stuck. How do I force uboot to use a different (already
known) serial port for the console? The drivers are there, it sees the port,
it just doesn't want to use it...



--
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