Hi Shimoda-san,
On Fri, Jan 28, 2022 at 1:09 AM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > From: Geert Uytterhoeven, Sent: Thursday, January 27, 2022 8:06 PM
>
> > On Tue, Jan 25, 2022 at 6:33 PM Yoshihiro Shimoda
> > <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > > Document the compatible values for the IPMMU-VMSA blocks in
> > > the Renesas R-Car S4-8 (R8A779F0) SoC and R-Car Gen4.
> > >
> > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > > --- a/Documentation/devicetree/bindings/iommu/renesas,ipmmu-vmsa.yaml
> > > +++ b/Documentation/devicetree/bindings/iommu/renesas,ipmmu-vmsa.yaml
> > > @@ -44,6 +44,10 @@ properties:
> > > - renesas,ipmmu-r8a77990 # R-Car E3
> > > - renesas,ipmmu-r8a77995 # R-Car D3
> > > - renesas,ipmmu-r8a779a0 # R-Car V3U
> > > + - items:
> > > + - enum:
> > > + - renesas,ipmmu-r8a779f0 # R-Car S4-8
> > > + - const: renesas,rcar-gen4-ipmmu-vmsa # R-Car Gen4
> > >
> >
> > I'm wondering if we need the family-specific fallback.
> > For R-Car Gen3, we don't have it, and match on (all) the SoC-specific
> > compatible values instead.
> > Do you remember why we decided to do it that way?
> >
> > At least R-Car V3M/V3H/D3 have slight differences in the register bits,
> > but I don't think that was the reason.
>
> I don't remember why... Maybe, we had never discussed this topic?
> I searched this topic a little on the ML archive, but I could not find it...
Indeed. I also couldn't find a discussion, and most IPMMUs on R-Car
Gen3 SoCs are identical (although there are differences in parts we
don't use in the driver). The IPMMUs in early R-Car Gen3 SoCs also had
issues, so that's probably why we never went with a family-specific
compatible value. And adding it now wouldn't gain us much.
> Since upcoming R-Car Gen4 SoC's IPMMU is the same specification with r8a779f0,
> I believe renesas,rcar-gen4-ipmmu-vmsa is helpful to support it.
Agreed.
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
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
