Le 21/02/2018 à 15:42, Jonathan Neuschäfer a écrit :

Hi,

On Wed, Feb 21, 2018 at 08:06:10AM +0100, Christophe LEROY wrote:

quoted

Le 20/02/2018 à 17:14, Jonathan Neuschäfer a écrit :

quoted

This patchset adds support for DISCONTIGMEM on 32-bit PowerPC. This is
required to properly support the Nintendo Wii's memory layout, in which
there are two blocks of RAM and MMIO in the middle.

Previously, this memory layout was handled by code that joins the two
RAM blocks into one, reserves the MMIO hole, and permits allocations of
reserved memory in ioremap. This hack didn't work with resource-based
allocation (as used for example in the GPIO driver for Wii[1]), however.

After this patchset, users of the Wii can either select CONFIG_FLATMEM
to get the old behaviour, or CONFIG_DISCONTIGMEM to get the new
behaviour.

My question might me stupid, as I don't know PCC64 in deep, but when looking
at page_is_ram() in arch/powerpc/mm/mem.c, I have the feeling the PPC64
implements ram by blocks. Isn't it what you are trying to achieve ? Wouldn't
it be feasible to map to what's done in PPC64 for PPC32 ?

Using page_is_ram in __ioremap_caller and the same memblock-based
approach that's used on PPC64 on PPC32 *should* work, but I think due to
the following line in initmem_init, it won't:

	memblock_set_node(0, (phys_addr_t)ULLONG_MAX, &memblock.memory, 0);

Can't we just fix that ?

Christophe

Thanks,
Jonathan Neuschäfer