[U-Boot] One u-boot.bin for Raspberry PI 3 and 4 - possible?

Matthias Brugger matthias.bgg at gmail.com
Mon Sep 30 09:03:32 UTC 2019

On 29/09/2019 07:13, Geoff Williams wrote:
> Hi Matthias,
>>> 1. On the PI 4 with mainline u-boot the screen turns yellow and wraps around on
>>> itself a second or so into the linux boot (grub screen is fine). With the patch
>>> applied I get the same behaviour on the PI3. Everything still works
>>> the screen is
>>> just messed up.
>> Ok, the problem on the RPi3 honestly surprising. I'll have to check myself
>> what's happening there. BTW when you talk about linux, do you use the downstream
>> kernel for that?
> I've been using a self-compiled kernel using sources from
> https://github.com/raspberrypi/linux and tag raspberrypi-kernel_1.20190819-1.
> I re-tested this by swapping to downstream kernel 4.19.75 from
> https://github.com/raspberrypi/firmware commit
> f5c626c64874d6e1482edf4a76aa22e5e54be63d (latest). Tried hdmi_safe=1 and
> same problem. I have copied all of the DTB files and overlays from upstream to
> the root of the memory card FAT partition and the kernel modules from firmware
> modules directory to /lib/modules - same result
>>> If I instead use rpi_3_defconfig, I get a rainbow screen on the PI4 and the
>>> screen goes switches off instead of just turning yellow on the PI3.
>> It's exepcted that RPi4 won't boot with rpi_3_defconfig. Background is, that
>> RPi3 defconfig uses still embedded device tree which does not boot on RPi4.
> That makes sense, this problem will probably go away once a combined defconfig
> is available.
>> On the other hand RPi4 defconfig uses the devicetree provided by the FW, that's
>> why it also (somehow) works on RPi3. It's on my todo-list to create one single
>> config for both RPi3 and RPi4, that wasn't done until now.
> This would be perfect, at the moment I'm just using the RPi4 version for both
> systems and this works fine apart from the screen and keyboard issues.
>> I'm not sure if you mean that the screen getting switched off on the RPi3 with
>> rpi_3_defconfig is a regression or if this is the behaviour you expect.
> I would expect the screen to stay on ;-). rpi_3_defconfig causes the screen to
> switch off right after the bcm2835-codec kernel module loads whereas
> rpi_4_defconfig causes a yellow screen on both boards almost instantly.

And with a U-Boot based on f5c626c64874d6e1482edf4a76aa22e5e54be63d without my
patches you see correct behavior?


>>> 2. USB wireless keyboard doesn't work until Linux loads on both systems if
>>> built with rpi_4_defconfig. I tried copying settings from rpi_3_defconfig[1] but
>>> then keyboard didn't work on either system.
>> Try to add CONFIG_USE_PREBOOT=y
>> but that should only give you USB on the type-c connector. USB on the type-b
>> connector isn't expect to work.
> My wireless keyboard has a type-a dongle so that's why it won't work yet.
> Thanks,
> Geoff
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