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, Fab > > > "renesas,i2c-r8a774a1" if the device is a part of a R8A774A1 SoC. > > "renesas,i2c-r8a7778" if the device is a part of a R8A7778 SoC. > > "renesas,i2c-r8a7779" if the device is a part of a R8A7779 SoC. > > -- > > 2.7.4 > > Renesas Electronics Europe Ltd, Dukes Meadow, Millboard Road, Bourne End, Buckinghamshire, SL8 5FH, UK. Registered in England & Wales under Registered No. 04586709.
