Re: [PATCH 2/2] iommu/ipmmu-vmsa: Add support for r8a779a0

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Shimoda-san,

On Tue, Sep 7, 2021 at 2:02 AM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@renesas.com> wrote:
> > From: Geert Uytterhoeven, Sent: Tuesday, September 7, 2021 12:34 AM
> > On Wed, Sep 1, 2021 at 12:27 PM Yoshihiro Shimoda
> > <yoshihiro.shimoda.uh@renesas.com> wrote:
> > > Add support for r8a779a0 (R-Car V3U). The IPMMU hardware design
> > > of this SoC differs than others. So, add a new ipmmu_features for it.
> > >
> > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> >
> > > --- a/drivers/iommu/ipmmu-vmsa.c
> > > +++ b/drivers/iommu/ipmmu-vmsa.c
> >
> > > @@ -922,6 +922,20 @@ static const struct ipmmu_features ipmmu_features_rcar_gen3 = {
> > >         .utlb_offset_base = 0,
> > >  };
> > >
> > > +static const struct ipmmu_features ipmmu_features_r8a779a0 = {
> > > +       .use_ns_alias_offset = false,
> > > +       .has_cache_leaf_nodes = true,
> > > +       .number_of_contexts = 8,
> >
> > Shouldn't this be 16?
> > Or do you plan to add support for more than 8 contexts later, as that
> > would require increasing IPMMU_CTX_MAX, and updating ipmmu_ctx_reg()
> > to handle the second bank of 8 contexts?
>
> I would like to add support for more than 8 contexts later because
> I realized that ctx_offset_{base,stride} are not suitable for the second bank
> of 8 contexts...

Wouldn't something like below be sufficient?

 static unsigned int ipmmu_ctx_reg(struct ipmmu_vmsa_device *mmu,
                                  unsigned int context_id, unsigned int reg)
 {
-       return mmu->features->ctx_offset_base +
-              context_id * mmu->features->ctx_offset_stride + reg;
+       unsigned int base = mmu->features->ctx_offset_base;
+
+       if (context_id > 7)
+               base += 0x800 - 8 * 0x1040;
+
+       return base + context_id * mmu->features->ctx_offset_stride + reg;
 }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

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
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