On Friday 19 February 2016 14:29:00 Chris Brandt wrote:

On 19 Feb 2016, Arnd Bergmann wrote:

quoted

On Thursday 18 February 2016 11:02:33 Nicolas Pitre wrote:

quoted

Acked-by: Nicolas Pitre <redacted>

Is there a way to provide a default for defaults?

We could have something like

config PHYS_OFFSET_0
	bool

config PHYS_OFFSET_1
	bool

config PHYS_OFFSET_2
	bool

... (we need 8 of the 16 possible addresses)


config PHYS_OFFSET
	hex "Physical address of main memory" if MMU
	default DRAM_BASE if !MMU
	default 0x00000000 if PHYS_OFFSET_0
	default 0x10000000 if PHYS_OFFSET_1
	default 0x20000000 if PHYS_OFFSET_2
	default 0x30000000 if PHYS_OFFSET_3
	default 0x70000000 if PHYS_OFFSET_7
	default 0x80000000 if PHYS_OFFSET_8
	default 0xa0000000 if PHYS_OFFSET_A
	default 0xc0000000 if PHYS_OFFSET_C


and then select one of the bool symbols from each platform.
Would that address your question?

Here's a question:

Can we just get rid of PHYS_OFFSET???

If it's only used at boot for XIP systems, we could:

A) pass it in via an unused register like atags and DT
 or
B) just assume that atags or DT is in RAM, so round down to the nearest section and assume that is the start of your RAM

If it is needed after initial boot, then on first boot we save what was passed in from the boot loader for later use.

Hmm, you mean making phys_offset a runtime variable instead
of patching it at early boot time in the instructions?

I have no idea if that works, how much effort it would be,
or how much it would enlarge the kernel image size, but
you can definitely try.

Of course we must not break existing platforms using XIP_KERNEL
already, but the installed base among systems that are upgrading
to modern kernels is very small now, given how all modern platforms
don't support XIP_KERNEL today, or have no MMU to start with.

	Arnd