sh: Make PAGE_OFFSET configurable.

nommu needs to be able to shift PAGE_OFFSET, so we switch it to a
non-user-visible CONFIG_PAGE_OFFSET and use that in the few places
where it matters.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/mm/Kconfig

@@ -161,6 +161,37 @@ config MMU
 	  turning this off will boot the kernel on these machines with the
 	  MMU implicitly switched off.
 
+config PAGE_OFFSET
+	hex
+	default "0x80000000" if MMU
+	default "0x00000000"
+
+config MEMORY_START
+	hex "Physical memory start address"
+	default "0x08000000"
+	---help---
+	  Computers built with Hitachi SuperH processors always
+	  map the ROM starting at address zero.  But the processor
+	  does not specify the range that RAM takes.
+
+	  The physical memory (RAM) start address will be automatically
+	  set to 08000000. Other platforms, such as the Solution Engine
+	  boards typically map RAM at 0C000000.
+
+	  Tweak this only when porting to a new machine which does not
+	  already have a defconfig. Changing it from the known correct
+	  value on any of the known systems will only lead to disaster.
+
+config MEMORY_SIZE
+	hex "Physical memory size"
+	default "0x00400000"
+	help
+	  This sets the default memory size assumed by your SH kernel. It can
+	  be overridden as normal by the 'mem=' argument on the kernel command
+	  line. If unsure, consult your board specifications or just leave it
+	  as 0x00400000 which was the default value before this became
+	  configurable.
+
 config 32BIT
 	bool "Support 32-bit physical addressing through PMB"
 	depends on CPU_SH4A