U-Boot failures on CM4 and Pi4-8Gb

[Matthias Brugger]

Hi Dave,

On 16/12/2020 15:23, Dave Jones wrote:
> Hi,
> 
> We've recently run across some failures with U-Boot on a couple of platforms,
> specifically the relatively new Pi Compute Module 4, and the Pi 4 8GB of RAM. On
> the CM4, U-Boot failed to identify the eMMC storage, and on the Pi 4 8GB, a
> crash and reset occurred when U-Boot tried to read from the boot file-system on
> the SD card, but only when booted with no monitor attached (attaching a monitor
> results in a successful boot, at least under arm64). These were with
> more-or-less stock rpi_4_defconfig and rpi_4_32b_defconfig configurations from
> v2020.10 (our local config changes bump the env-size, enable OF_BOARD, and
> RAW_INITRD, but that's it).
> 
> I've bisected the source and figured out roughly the commits responsible; for
> the CM4 eMMC case it's the enabling of DMA for the SDHCI interface in c6b9fbf756.
> 
> The Pi 4 8GB failure was a little more complex in that the bisection pointed to
> 3113c84ba2 (a merge), however that gave me a few clues to try and after a little
> experimenting I found that disabling CONFIG_PCI_BRCMSTB (effectively disabling
> the PCI driver for the platform) got things working happily again.
> 
> I'm happy to submit the local patches I'm adding to the Ubuntu build to work
> around these, but obviously those fixes are "brute force and ignorance" patches
> that just disable the relevant config; would such patches be wanted, or would
> the community prefer to figure out the root causes in each case? I'm happy to
> test any patches on the relevant hardware if anyone doesn't have access to the
> necessary boards.
> 

Thanks for looking into this. I'm aware of problems booting CM4 and RPi 400 with
PCI. I wasn't aware that RPi4 8GB problem was related to PCI as well. Would you
mind to test this series, if this fixes your problems:
https://patchwork.ozlabs.org/user/todo/uboot/?series=220661

Regards,
Matthias