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

[Geert Uytterhoeven]

Hi Maciej,

On Mon, 19 Oct 2026 at 16:47, Maciej W. Rozycki <macro@xxxxxxxxxxx> wrote:
> > >  So oddly enough we're missing Tx49 support in the toolchain and we've
> > > only managed to survive with CPU_HAS_PREFETCH enabled for CPU_TX49XX
> > > because it also implies DMA_NONCOHERENT via MACH_TX49XX -> MACH_TXX9,
> > > which in turn disables stuff in arch/mips/lib/memcpy.S.
> > >
> > >  Quite straighforward to fix in binutils since docs are available (as in:
> > > I have a copy), but do we have any users?  Geert?
> >
> > Yes, I still boot test rbtx4927 regularly.
>
>  Thanks for confirming.
>
> > I never touched binutils sources, though...
>
>  No worries, this seems straightforward: just PREF, MADD/U plus [D]MULT/U
> extensions, and DERET/SDBBP debug stuff, much of which shared with the
> Tx39 we already support, so just a matter of sticking another flag onto
> the existing opcode table entries.
>
>  I'd estimate it as one day worth of engineering effort plus maybe another
> one for machines to work through verification, for the binutils side and
> the associated changes needed for GCC, i.e. a `-march=' option update plus
> maybe enabling a couple of existing machine description patterns for the
> Tx49 too.  Would you be able to run GCC verification with your system?

The rbtx4927 is about the slowest system I still do regular testing on.
It uses a Debian 8 nfsroot (over 10 Mbps Ethernet), which is the latest
Debian release still supporting the instruction subset suppported
by TX49XX.
So as long as no native compilation of large packages is required,
it can be done.  I can also give you remote access?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds