Re: [PATCH] powerpc/microwatt: Add mmu bits to device tree

[Michael Neuling <mikey@neuling.org>]

On Fri, 2022-05-20 at 10:06 +1000, Nicholas Piggin wrote:
> Excerpts from Joel Stanley's message of May 19, 2022 10:57 pm:
> > In commit 5402e239d09f ("powerpc/64s: Get LPID bit width from device
> > tree") the kernel tried to determine the pid and lpid bits from the
> > device tree. If they are not found, there is a fallback, but Microwatt
> > wasn't covered as has the unusual configuration of being both !HV and bare
> > metal.
> > 
> > Set the values in the device tree to avoid having to add a special case.
> > The lpid value is the only one required, but add both for completeness.
> > 
> > Fixes: 5402e239d09f ("powerpc/64s: Get LPID bit width from device tree")
> > Signed-off-by: Joel Stanley <joel@jms.id.au>
> 
> LGTM... does Microwatt actually need 12 lpid bits, or does it just need 
> the LPID 0 partition table entry? 

Microwatt just assumes LPID=0 as it doesn't actually have an LPID SPR. It just
uses the first entry in the partition table.

There are some details here:

   https://github.com/antonblanchard/microwatt/commit/18120f153d138f733fa7e8a89c3456bb93683f96

> I wonder if you set it to 1. That's a minor nit though.

.. or even set it to 0.

Mikey