RPi4 U-Boot freeze

[Matthias Brugger]

On 10/09/2020 23:12, Stefan Agner wrote:
> On 2020-09-07 16:36, Peter Robinson wrote:
>>> Any thoughts on this issue?
>>
>> Any reason why you're using 2020.01 and not at least 2020.07, or at
>> least seeing if it's reproducible on 2020.10-rc3? The RPi4 support has
>> changed quite a bit since then I suspect.
>>
> 
> Hi Peter,
> 
> It's a stable release and we support a couple of devices with the same
> U-Boot version. I'd rather prefer to stay with 2020.01 for RPi4 as well.
> 
> We are on 2020.07 on development branch, and it does work fine there. So
> I thought it can't be that hard, just bisect and backport whatever fixes
> it... Unfortunately, it seems that there is no particular commit which
> fixes it (the bisect ended up in a random unrelated commit, and it seems
> that the issue appears/disappears depending on alignment/size...).
> 
> I also did applied pretty much every RPi4 related commit made after
> 2020.01 up until master back to 2020.01, no success either.
> 

Which version of the Raspberry Pi firmware did you use?
Unfortunately changes in the FW breaks stuff on U-Boot from time to time.

Regards,
Mathias

> I fear that the problem in fact is still in master, but only appears if
> certain things align a certain way... That is why I thought I bring it
> up, to see if anybody else has noticed something along this lines. We do
> have a rather trimmed down configuration, which might make the problem
> appear more (fit in a D cache...).
> 
> I probably will just disable cached around relocation for 2020.01 and
> see if it resurfaces on development branch.
> 
> --
> Stefan
> 
> 
>>> 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
>