Re: [PATCH 0/6] DISCONTIGMEM support for PPC32

[Christophe LEROY]

Le 21/02/2018 Ã 15:42, Jonathan NeuschÃfer a ÃcritÂ:
> Hi,
>
> On Wed, Feb 21, 2018 at 08:06:10AM +0100, Christophe LEROY wrote:
> > Le 20/02/2018 Ã 17:14, Jonathan NeuschÃfer a ÃcritÂ:
> > > 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 NeuschÃfer