Any thoughts on this issue?
Just to be sure, I did some memory testing on the 2GB module, but no issues found.
I still somehow suspected that something else might be wrong with my hardware, so I bought a new RPi4 (this time with 4GB of RAM) but the very same with that:
U-Boot 2020.01 (Aug 23 2020 - 22:02:31 +0000)
DRAM: 3.9 GiB <freeze>
I still think there is something wrong with caching. From what I understand caches are enabled by the RPi (4) firmware. Is it safe to run 32-bit ARM U-Boot with enabled caches?
-- Stefan
On 2020-08-23 19:06, Stefan Agner wrote:
Hi,
I noticed a quite common freeze when running 32-bit U-Boot 2020.01 (rpi_4_32b_defconfig) on a 2GB RPi4 model:
U-Boot 2020.01 (Aug 07 2020 - 13:00:23 +0000)
DRAM: 1.9 GiB <freeze, no more output>
This happens fairly often, I would say 4 out of 5 boot tries. However, if it boots, everything seems to run fine.
The issue seems to go away when using 2020.04 or any newer release, however, when trying to find the actual patch fixing the issue using git bisect I ended up with a MMC merge request which really seems unrelated (36bdcf7f3b). It seems that the problem is quite evasive and disappears if certain structure are aligned differently etc.
Enabling initcall debugging showed that U-Boot crashes right after relocation:
... initcall: 00016f2c
RAM Configuration: Bank #0: 0 948 MiB Bank #1: 40000000 1 GiB Bank #2: 0 0 Bytes Bank #3: 0 0 Bytes
DRAM: 1.9 GiB initcall: 00016bb8 New Stack Pointer is: 3af6d9e0 initcall: 00016da4 initcall: 00016ef0 initcall: 00016ef8 initcall: 00016d38 Relocation Offset is: 3b375000 Relocating to 3b37d000, new gd at 3af78ec0, sp at 3af6d9e0 initcall: 00016ec8 [clear_bss] initcall: 0004465c [display_options?? only appears sometimes]
<freeze>
I realized when using CONFIG_SYS_(I|D)CACHE_OFF=y the problem seems to disappear. But to be 100% certain that it is cache related, I used my original configuration (which is known to "reliably" freeze), and replaced 00016ec8 with 00008688 manually in the binary, essentially swapping out function pointers in "init_sequence_f" [00008688 is cleanup_before_linux, which flushes and disables I-cache/D-cache]. And indeed, that hacked up binary does boot reliably every time:
... initcall: 00016f2c
RAM Configuration: Bank #0: 0 948 MiB Bank #1: 40000000 1 GiB Bank #2: 0 0 Bytes Bank #3: 0 0 Bytes
DRAM: 1.9 GiB initcall: 00016bb8 New Stack Pointer is: 3af6d9e0 initcall: 00016da4 initcall: 00016ef0 initcall: 00016ef8 initcall: 00016d38 Relocation Offset is: 3b375000 Relocating to 3b37d000, new gd at 3af78ec0, sp at 3af6d9e0 initcall: 00008688 initcall: 3b38c10c initcall: 3b38c114 initcall: 000172e0 (relocated to 3b38c2e0) initcall: 0001712c (relocated to 3b38c12c) ...
From what I understand on RPi4 caches are enabled when entering U-Boot. I was wondering if the relocation code really can handle that?
-- Stefan