Subject: Re: [PATCH 1/2] powerpc/85xx: fix problem that prevents PHYS_64BIT from configurable

From: Scott Wood <[email-masked]>
Date: Mon, 20 Feb 2012 14:30:27 -0600

On 02/17/2012 08:19 PM, Benjamin Herrenschmidt wrote:
> On Fri, 2012-02-17 at 18:56 -0600, Scott Wood wrote:
>> Yes, or maybe make it "default y", and/or require an "I know what I'm
>> doing" option to be set for it to be unset if a board otherwise wants it.
>>
>> The ability to turn it off is potentially useful for any board, since
>> the address map is determined by boot software which can be changed, but
>> we shouldn't make it too easy to fail to select it for boards that
>> normally require it.
> 
> Don't we have CONFIG_EMBEDDED to make that sort of option visible ?

OK, so:

config WANT_PHYS_64BIT
select PHYS_64BIT if !EMBEDDED

config PHYS_64BIT
default y if WANT_PHYS_64BIT

...and "select WANT_PHYS_64BIT" on boards that normally have 36-bit
address maps?

What about 86xx?  It looks like PHYS_64BIT can't be enabled if it's
sharing a kernel image with 82xx or 83xx (why these specific SoCs but
not 603 in general?).

-Scott