[PATCH] rpi: always set fdt_addr to the correct value

[Marek Szyprowski]

Hi Matthias,

On 15.02.2022 19:19, Matthias Brugger wrote:
>
> On 15/02/2022 15:55, Matthias Brugger wrote:
>>
>> On 18/02/2022 03:44, Jaehoon Chung wrote:
>>> On 22. 2. 14. 20:25, Marek Szyprowski wrote:
>>>> The fdt_addr env have meaning only for the current runtime and it 
>>>> depends
>>>> on the dtb size or firmware version. If one save the environment to 
>>>> disk
>>>> and the loads it on the latter boot, the fdt_addr might change, what
>>>> result in passing incorrect dtb address to the kernel. Fix this by 
>>>> always
>>>> setting the fdt_addr env. This fixes system operation after saving the
>>>> env to disk and updating i.e. dtb files or firmware.
>>>>
>>>> Signed-off-by: Marek Szyprowski <m.szyprowski at samsung.com>
>>>
>>> Reviewed-by: Jaehoon Chung <jh80.chung at samsung.com>
>>>
>>
>> Could we keep the discussion where we left it the last time you 
>> submitted the patch?
>>
>
> I forgot to add the link to the old discussion:
> https://patchwork.ozlabs.org/project/uboot/patch/20210512123945.25649-1-m.salvini@koansoftware.com/

Well, I'm still not convinced that this is a good idea.

I found this issue while debugging something else and I must admit that 
the current behavior is really counterintuitive. I was surprised that 
after setting some really unrelated things in u-boot's envs (like 
additional kernel arguments to increase debug level) and saving such 
config, I got completely broken system. Right, I've also updated DTB in 
meantime because I was bisecting some kernel related issue, but still 
this is something that a typical user might face during system update.

If we want to keep current behavior, the 'saveenv' command should print 
a large banner that one has to first delete the 'fdt_addr' env if he 
wants to have a working system.

I will check if it would be possible to use some flags for the 
'fdt_addr' env to mark it as 'do-not-save-unless-changed-manually'.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland