Dear all,

I am trying to understand how to change the default pin of the u-boot (2020.01) console for the Raspberry pi CM3+ board.

I am using yocto with meta-raspberrypi on the dunfell branch and how everything works between the first stage bootloader, u-boot, u-boot internal device tree and the kernel device tree is not really clear to me.

Here is what I would like to achieve:

1. Get UART0 or UART1 as the standard console for u-boot and the linux kernel on pins 32 and 33 2. Make u-boot pass my device tree (stored in the boot partition) to the kernel and not the device tree generated by the first stage bootloader

Regarding the first point, I already created a new device tree within u-boot and set it as the default bootloader in my default config (see attached files). Here is the different things I tried:

* Use UART0 on pins 32 and 33 * In the u-boot device tree:

chosen { stdout-path = "serial0:115200n8"; } ... &uart0 { pinctrl-names= "default"; pinctrl-0 = <&uart0_gpio32>; status = "okay"; }

* In the config.txt:

enable_uart=1 dtoverlay=uart0,txd0_pin=32,rxd0_pin=33,pin_func=7

* This works but only for the kernel, I don't get any output from u-boot and can't stop the boot process.

* Use UART1 on pins 32 and 33: more or less the same modification but with different values

I would like to know if there is an other file I should modify to get this working. When I use the uart0 or uart1 on pin 14 and 15 everything works properly.

The second point seems pretty clear to me. I will change the bootscript and load the file with the fatload command and pass it to the kernel. However I wonder if it might create some problems if the first stage bootloader has already reserved the pins.

Finally when u-boot is starting correctly I have the following warning and I was not able to find any explanation on it:

U-Boot 2020.01 (Jan 06 2020 - 20:56:31 +0000)

DRAM: 948 MiB RPI Compute Module 3+ (0xa02100) MMC: mmc@7e202000: 0 Loading Environment from FAT... WARNING at drivers/mmc/bcm2835_sdhost.c:410/bcm2835_send_command()! WARNING at drivers/mmc/bcm2835_sdhost.c:410/bcm2835_send_command()! *** Warning - bad CRC, using default environment

In: serial Out: vidconsole Err: vidconsole Net: No ethernet found. starting USB... Bus usb@7e980000: scanning bus usb@7e980000 for devices... 1 USB Device(s) found scanning usb for storage devices... 0 Storage Device(s) found Hit any key to stop autoboot: 0 WARNING at drivers/mmc/bcm2835_sdhost.c:410/bcm2835_send_command()! WARNING at drivers/mmc/bcm2835_sdhost.c:410/bcm2835_send_command()! switch to partitions #0, OK mmc0(part 0) is current device Scanning mmc 0:1... Found U-Boot script /boot.scr Should I simply ignore it ?

Thank you in advance for your time.

Best regards Romain ________________________________ Romain Crausaz

Development

DIGI SENS Switzerland AG Freiburgstr. 65 CH-3280 Murten

Telefon: +41 26 672 9876 Email: romain.crausaz@digisens.chmailto:romain.crausaz@digisens.ch

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