[U-Boot] [PATCH v2 8/9] efi_loader: do not use magic address for fdt

Alexander Graf agraf at suse.de
Tue Nov 13 22:22:08 UTC 2018



On 13.11.18 22:31, Heinrich Schuchardt wrote:
> On 11/13/18 10:21 PM, Alexander Graf wrote:
>>
>>
>> On 12.11.18 18:55, Heinrich Schuchardt wrote:
>>> We currently place the flattened device tree 127 MiB from the start of the
>>> first memory bank. This may be in a reserved memory area.
>>>
>>> So let's change the sequence: first create memory reservations and then
>>> copy the device tree.
>>>
>>> Do not use any magic address.
>>>
>>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>>
>> This would be a regression over commit
>> ad0c1a3d2cea03011091b07e9e066bf261d1556e no?
> 
> From your commit in ad0c1a3d2cea03011091b07e9e066bf261d1556e message I
> cannot infer which address would pose a problem and why.

Yeah, I was pretty disappointed with my commit message too :(.

It does mention Andreas. Maybe he remembers something?

> 
> You only mentioned it should be a place where the fdt can stay. Isn't
> this any address in a reserved memory area?
> 
> You did not provide any reference to a document recommending that an
> address around 128 MB should be favorable. Was the memory reservation
> missing at that time?

I really don't remember the details. It was something pretty dumb,
that's as far as my memory goes.

My point is that this is an explicit workaround for a real world problem
that existed. I see little reason to remove the workaround at this point
without proper validation that it's no longer needed. Unfortunately at
least for us ARMv7 is completely busted right now, because our kernel
binary became too big. So I don't have a good playground to do any
verification on.


Alex


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