RPi3: serial console

[Heinrich Schuchardt]

On 10/12/20 6:50 PM, Peter Robinson wrote:
> On Mon, Oct 12, 2020 at 3:56 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>
>> Hello Matthias,
>>
>> I have upgraded the Raspberry 3 firmware from raspi3-firmware
>> (1.20190215-1+deb10u4) to raspi-firmware (1.20200601-3)
>> [https://packages.debian.org/bullseye/raspi-firmware].
>>
>> After the upgrade the output of U-Boot on the serial console is complete
>> gibberish as if the baudrate were incorrect. The output from the Linux
>> kernel is fine at 115200 baud.
>
> I've seen similar on all firmware since around mid April up until
> recently, it seems to be fixed with releases in Oct (I'm using one
> from Oct 8th), I'm not sure if it can be fixed in U-Boot but it seems
> to be due to a change in the firmware.

Thanks for confirming the problem.

Using the most current files from
https://github.com/raspberrypi/firmware does not solve the problem for me.

In bcm283x_mu_serial_setbrg() we divide a clock rate by the baudrate.
divider = plat->clock / (baudrate * 8);

If we do not have the correct clock rate, the actual baudrate will be wrong.

Best regards

Heinrich

>
>> I observe this both with rpi_3_defconfig and rpi_arm64_defconfig,
>> v2020.10 and current origin/master.
>>
>> config.txt:
>>
>> arm_control=0x200
>> enable_uart=1
>> upstream_kernel=1
>> kernel=u-boot.bin
>>
>> boot.scr:
>> setenv autoload no
>> dhcp
>> load mmc 0:1 $fdt_addr_r bcm2710-rpi-3-b-plus.dtb
>> load mmc 0:2 $kernel_addr_r EFI/debian/grubaa64.efi
>> bootefi $kernel_addr_r $fdt_addr_r
>>
>> Best regards
>>
>> Heinrich