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

[Nicholas Piggin <npiggin@gmail.com>]

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

Acked-by: Nicholas Piggin <npiggin@gmail.com>

> ---
>  arch/powerpc/boot/dts/microwatt.dts | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/boot/dts/microwatt.dts b/arch/powerpc/boot/dts/microwatt.dts
> index 65b270a90f94..b69db1d275cd 100644
> --- a/arch/powerpc/boot/dts/microwatt.dts
> +++ b/arch/powerpc/boot/dts/microwatt.dts
> @@ -90,6 +90,8 @@ PowerPC,Microwatt@0 {
>  			64-bit;
>  			d-cache-size = <0x1000>;
>  			ibm,chip-id = <0>;
> +			ibm,mmu-lpid-bits = <12>;
> +			ibm,mmu-pid-bits = <20>;
>  		};
>  	};
>  
> -- 
> 2.35.1
> 
>