On Mon, Sep 24, 2018 at 09:10:53AM +0000, Fabrizio Castro wrote: > Hello Simon, > > Thank you for the feedback. > > > Subject: Re: [PATCH 1/4] dt-bindings: i2c: rcar: Add r8a77470 support > > > > On Fri, Sep 21, 2018 at 06:36:58PM +0100, Fabrizio Castro wrote: > > > Although the I2C IP found in the RZ/G1C is not exactly the same > > > as the one found in the R-Car Gen2 family or R-Car Gen3 family, > > > it can still be considered as compatible with R-Car Gen2 from > > > a software perpective. > > > This patch therefore documents the SoC specific compatible string, > > > and the compatibility with Gen2 fallback is retained. > > > > > > Signed-off-by: Fabrizio Castro <fabrizio.castro@xxxxxxxxxxxxxx> > > > Reviewed-by: Biju Das <biju.das@xxxxxxxxxxxxxx> > > > --- > > > Documentation/devicetree/bindings/i2c/i2c-rcar.txt | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/Documentation/devicetree/bindings/i2c/i2c-rcar.txt b/Documentation/devicetree/bindings/i2c/i2c-rcar.txt > > > index 39cd21d..671e2a1 100644 > > > --- a/Documentation/devicetree/bindings/i2c/i2c-rcar.txt > > > +++ b/Documentation/devicetree/bindings/i2c/i2c-rcar.txt > > > @@ -4,6 +4,7 @@ Required properties: > > > - compatible: > > > "renesas,i2c-r8a7743" if the device is a part of a R8A7743 SoC. > > > "renesas,i2c-r8a7745" if the device is a part of a R8A7745 SoC. > > > +"renesas,i2c-r8a77470" if the device is a part of a R8A77470 SoC. > > > > It seems to me that the RZ/G1C has some extra registers described for > > I2C when compared with both other RZ/G1 and R-Car Gen2 SoCs. > > Exactly. The extra registers found with the RZ/G1C I2C controller are also found in R-Car Gen3, > but the driver doesn't handle them. R-Car Gen3 has more registers on top of those found > with the RZ/G1C. > > > > > Am I correct in assuming that operation is correct for the RZ/G1C > > when using the fallback compat string for RZ/G1 and R-Car Gen2 SoCs? > > Since the driver is not using ICCCR2, ICMPR, ICHPR, and ICLPR, what's left is compatible > with R-Car Gen2. > I have tested I2C4 on its own and with the HDMI transmitter found on the iwg23s, and > so far so good. > > > > > And that, speculating wildly, in future it may be possible for > > the driver to use these extra resgisters, f.e. by via a match on > > the renesas,i2c-r8a77470 compat string? > > Exactly. If anybody ever looks into supporting the missing functionality the SoC > specific string could be used to pick up better driver support (although Gen2 > support would probably still be alright). > > I hope this clarifies things a little bit better. Thanks, it helps a lot.
