Re: [RFC PATCH 02/17] powerpc: Split up PHYS_64BIT config option to fix "select" issues

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=