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From: Tabi Timur-B04825 <B04825@freescale.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [RFC PATCH 02/17] powerpc: Split up PHYS_64BIT config option to
 fix "select" issues
Date: Fri, 11 Nov 2011 13:12:31 +0000
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Cc: Wood Scott-B07421 <B07421@freescale.com>, Baruch Siach <baruch@tkos.co.il>,
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Benjamin Herrenschmidt wrote:

> For PHYS_64BIT, I'm not 100% certain at this point what the best
> approach it. It should clearly be fixed and hidden for real 64-bit. As
> for the rest, should it be user selectable ?

I have been unable to convince our BSP teams that the minor performance=20
improvement of a 32-bit kernel vs 36-bit is not worth the hassle.  We ship=
=20
a lot of lower-end e500 systems that will never have more than 2GB of memor=
y.

The P1022DS is an example.  We ship 32-bit and 36-bit versions of U-Boot,=20
the kernel, and the device tree.  I recently added code to U-boot to=20
detect if you have a mismatched U-Boot and device tree, because it is so=20
easy to mess that up.  I would like nothing more than to abandon 32-bit=20
for all e500, but I don't see Freescale allowing that any time soon.

--=20
Timur Tabi
Linux kernel developer at Freescale=