Subject: Re: [PATCH] powerpc/85xx: allow CONFIG_PHYS_64BIT to be selectable

From: Tabi Timur-B04825 <[email-masked]>
Date: Fri, 24 Feb 2012 04:11:13 +0000

Li Yang-R58472 wrote:

> It's a good point.  Why can't we decide to use 32-bit/36-bit TLB at runtime even for e500v2?

That's not what PHYS_64BIT does.  PHYS_64BIT determines whether 
phys_addr_t is a u64 or a u32.  This is something that must be determined 
at compilation time.

>> Please remember that the Kconfig for the P1022DS already forced
>> PHYS_64BIT for all mpc85xx platforms.  All we're doing is making it
>> possible to deselect PHYS_64BIT.
>
> I think it's a side-effect introduced by P1022DS support and need to be fixed.

Exactly.  That's what these patches do.  And these patches have been 
applied to the SDK.  I'm just waiting for Kumar to apply them to his 
repository.

> There was no mentioning of enforcing 36-bit for all mpc85xx platforms.

It's not enforcing, it's just the default.  If you build with 
mpc85xx_smp_defconfig, then you'll get a 36-bit kernel.  But now you can 
also use menuconfig to turn off PHYS_64BIT.  Before these fixes, that was 
not possible.

-- 
Timur Tabi
Linux kernel developer at Freescale