Re: [PATCH 1/6] MIPS: remove cpu_has_64bit_gp_regs and cpu_has_64bit_addresses

Christoph Hellwig
2020-03-25T09:54:39Z

On Wed, Mar 25, 2020 at 10:24:46AM +0100, Fredrik Noring wrote:
> > > The (slightly outdated) patch series under review
> > > is available here:
> > >
> > > https://lore.kernel.org/linux-mips/cover.1567326213.git.noring@nocrew.org/T/
> >
> > You don't happen to have a git tree available somewhere?
>
> https://github.com/frno7/linux/tree/ps2-v5.4
>
> is stable at v5.4,
>
> https://github.com/frno7/linux/tree/ps2-master
>
> has more experimental stuff (also at v5.4 at the moment). There are some
> (work-in-progress) notes on the R5900 psABI, that may be of interest, here:
>
> https://github.com/frno7/linux/wiki/R5900-processor-specific-ABI-(psABI)

So from what I can tell this uses a 32-bit kernel and 32-bit userspace,
and sets both pu_has_64bit_gp_regs and cpu_has_64bit_addresses to 0.

Now if you ever wanted to make use of the 64-bit registeres it would
require quite some changes, which probably really should have a new
Kconfig option. In fact a lot of the workaround for the 64-bit
registeres that are in the code already should be keyed off such an
option rather than CONFIG_CPU_R5900.