[PATCH] of/fdt: Remove PPC32 longtrail hack in memory scan

[Michael Ellerman]

Rob Herring <robh+dt at kernel.org> writes:
> On Thu, Jul 26, 2018 at 11:36 PM Michael Ellerman <mpe at ellerman.id.au> wrote:
>> When the OF code was originally made common by Grant in commit
>> 51975db0b733 ("of/flattree: merge early_init_dt_scan_memory() common
>> code") (Feb 2010), the common code inherited a hack to handle
>> PPC "longtrail" machines, which had a "memory at 0" node with no
>> device_type.
>>
>> That check was then made to only apply to PPC32 in b44aa25d20e2 ("of:
>> Handle memory at 0 node on PPC32 only") (May 2014).
>>
>> But according to Paul Mackerras the "longtrail" machines are long
>> dead, if they were ever seen in the wild at all. If someone does still
>> have one, we can handle this firmware wart in powerpc platform code.
>>
>> So remove the hack once and for all.
>
> Yay. I guess Power Macs and other quirks will never die...

Not soon.

In base.c I see:
 - the hack in arch_find_n_match_cpu_physical_id()
   - we should just move that into arch code, it's a __weak arch hook
     after all.
 - a PPC hack in of_alias_scan(), I guess we need to retain that
   behaviour, but it's pretty minor anyway.

In address.c there's the powermac empty ranges hack. Seems like we could
fix that just by creating empty `ranges` properties in fixup_device_tree().
I don't think we support booting powermacs other than via prom_init(). (Ben?)

> I'll queue this up.

cheers