[1/2] dt-bindings: iommu: renesas,ipmmu-vmsa: add r8a779f0 support

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@renesas.com>
---
 .../devicetree/bindings/iommu/renesas,ipmmu-vmsa.yaml         | 4 ++++
 1 file changed, 4 insertions(+)

Hi Shimoda-san,

CC Laurent, Magnus.

On Tue, Jan 25, 2022 at 6:33 PM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@renesas.com> 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@renesas.com>

Thanks for your patch!

> --- 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.

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

Hi Geert,

On Thu, Jan 27, 2022 at 12:05:31PM +0100, Geert Uytterhoeven wrote:
> On Tue, Jan 25, 2022 at 6:33 PM Yoshihiro Shimoda 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@renesas.com>
> 
> Thanks for your patch!
> 
> > --- 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?

I'm afraid I don't. You know my usual opinion of SoC-specific compatible
strings :-)

> At least R-Car V3M/V3H/D3 have slight differences in the register bits,
> but I don't think that was the reason.

Hi Geert-san,

Thank you for your review!

> From: Geert Uytterhoeven, Sent: Thursday, January 27, 2022 8:06 PM
> 
> Hi Shimoda-san,
> 
> CC Laurent, Magnus.
> 
> On Tue, Jan 25, 2022 at 6:33 PM Yoshihiro Shimoda
> <yoshihiro.shimoda.uh@renesas.com> 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@renesas.com>
> 
> Thanks for your patch!
> 
> > --- 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...

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.

Best regards,
Yoshihiro Shimoda

> 
> 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