Re: [PATCH] MIPS: lib: prefetch ahead in csum_partial()

[Maciej W. Rozycki]

On Fri, 9 Oct 2026, Rosen Penev wrote:

> diff --git a/arch/mips/lib/csum_partial.S b/arch/mips/lib/csum_partial.S
> index 3d2ff4118d79..f0ec47259ef4 100644
> --- a/arch/mips/lib/csum_partial.S
> +++ b/arch/mips/lib/csum_partial.S
> @@ -190,6 +190,21 @@ EXPORT_SYMBOL(csum_partial)
>  	 andi	t2, a1, 0x40
>  
>  .Lmove_128bytes:
> +#ifdef CONFIG_CPU_HAS_PREFETCH
> +	/*
> +	 * Fetch the block two iterations ahead, but only while it lies
> +	 * inside the buffer: on non-coherent systems a line prefetched
> +	 * past the end could belong to a buffer the device still owns.
> +	 */
> +	sltiu	t5, t8, 3
> +	bnez	t5, 2f
> +	 nop

 I don't like this manual delay slot scheduling, but it seems like a case 
for a larger clean-up of this file, so I'd be inclined to accept it.

> +	pref	0, 0x100(src)
> +	pref	0, 0x120(src)
> +	pref	0, 0x140(src)
> +	pref	0, 0x160(src)

 What about MIPSr6 though, which only has a span of -256..255 for the 
immediate offset in the machine instruction here?

  Maciej