Unexpected RPi5 Behavior with Saved U-Boot Environment

[Mauro Salvini]

On 27/03/25 16:54, Richard Weinberger wrote:
> Hi!
> 
> We recently started using U-Boot on various Raspberry Pi 5 boards
> with different hardware configurations.
> 
> While testing, Simon noticed unusual boot failures, such as the kernel
> failing to boot with no output or U-Boot reporting:
> "ERROR: Did not find a cmdline Flattened Device Tree."
> 
> Today, I spent time investigating these issues. It appears that U-Boot
> retrieves several variables from the Raspberry Pi firmware, with fdt_addr
> being particularly important.
> If the environment is saved, fdt_addr gets stored and takes precedence
> over what the firmware provides to U-Boot.
> 
> Interestingly, the RPi firmware seems to modify fdt_addr based on connected
> hardware.  Our experiments showed that even attaching an RPi camera module
> changes the computed fdt_addr and U-Boot reads from the wrong memory location.
> 
> As a result, saving the environment, whether via the saveenv command in U-Boot
> or fw_setenv in Linux, can lead to boot failures if the hardware configuration changes.
> 
> Do you have any suggestions for mitigating this issue?
> In my opinion, U-Boot should not override such critical variables.
> 
> Thanks,
> //richard
> 

Hi Richard,

could be related tho this [1]?

I sent this patch some years ago but was never accepted in u-boot tree.
But meta-rpi uses it in u-boot recipe [2].

Regards

[1] https://lists.denx.de/pipermail/u-boot/2021-May/449609.html
[2] 
https://github.com/agherzan/meta-raspberrypi/blob/master/recipes-bsp/u-boot/files/0001-rpi-always-set-fdt_addr-with-firmware-provided-FDT-address.patch

-- 
Mauro