linux-kernel - Re: [PATCH] dt-bindings: can: rcar

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Message-ID: <20180824082643.7eapxf72iuvkdw3j@verge.net.au>
Date:   Fri, 24 Aug 2018 10:26:44 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Chris Paterson <Chris.Paterson2@...esas.com>
Cc:     Fabrizio Castro <fabrizio.castro@...renesas.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Biju Das <biju.das@...renesas.com>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dt-bindings: can: rcar_can: Add r8a774a1 support

On Wed, Aug 22, 2018 at 03:12:26PM +0000, Chris Paterson wrote:
> Hello Simon,
> 
> > From: Simon Horman <horms@...ge.net.au>
> > Sent: 22 August 2018 11:49
> > 
> > On Fri, Aug 17, 2018 at 03:38:23PM +0100, Fabrizio Castro wrote:
> > > Document RZ/G2M (r8a774a1) SoC bindings.
> > >
> > > Signed-off-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
> > > Reviewed-by: Biju Das <biju.das@...renesas.com>
> > 
> > Reviewed-by: Simon Horman <horms+renesas@...ge.net.au>
> 
> Thank you.
> 
> > 
> > > ---
> > > This patch applies on top of next-20180817
> > >
> > >  Documentation/devicetree/bindings/net/can/rcar_can.txt | 8 ++++++--
> > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/Documentation/devicetree/bindings/net/can/rcar_can.txt
> > > b/Documentation/devicetree/bindings/net/can/rcar_can.txt
> > > index 94a7f33..84afc78 100644
> > > --- a/Documentation/devicetree/bindings/net/can/rcar_can.txt
> > > +++ b/Documentation/devicetree/bindings/net/can/rcar_can.txt
> > > @@ -4,6 +4,7 @@ Renesas R-Car CAN controller Device Tree Bindings
> > > Required properties:
> > >  - compatible: "renesas,can-r8a7743" if CAN controller is a part of R8A7743
> > SoC.
> > >  	      "renesas,can-r8a7745" if CAN controller is a part of R8A7745 SoC.
> > > +	      "renesas,can-r8a774a1" if CAN controller is a part of R8A774A1 SoC.
> > >  	      "renesas,can-r8a7778" if CAN controller is a part of R8A7778 SoC.
> > >  	      "renesas,can-r8a7779" if CAN controller is a part of R8A7779 SoC.
> > >  	      "renesas,can-r8a7790" if CAN controller is a part of R8A7790 SoC.
> > > @@ -16,7 +17,8 @@ Required properties:
> > >  	      "renesas,rcar-gen1-can" for a generic R-Car Gen1 compatible device.
> > >  	      "renesas,rcar-gen2-can" for a generic R-Car Gen2 or RZ/G1
> > >  	      compatible device.
> > > -	      "renesas,rcar-gen3-can" for a generic R-Car Gen3 compatible device.
> > > +	      "renesas,rcar-gen3-can" for a generic R-Car Gen3 or RZ/G2
> > > +	      compatible device.
> > >  	      When compatible with the generic version, nodes must list the
> > >  	      SoC-specific version corresponding to the platform first
> > >  	      followed by the generic version.
> > > @@ -24,7 +26,9 @@ Required properties:
> > >  - reg: physical base address and size of the R-Car CAN register map.
> > >  - interrupts: interrupt specifier for the sole interrupt.
> > >  - clocks: phandles and clock specifiers for 3 CAN clock inputs.
> > > -- clock-names: 3 clock input name strings: "clkp1", "clkp2", "can_clk".
> > > +- clock-names: 2 clock input name strings for RZ/G2: "clkp1",
> > > +"can_clk", and
> > 
> > Minor comment: Personally I would start a new sentence at "and".
> > 
> > Question: Is a driver update required so support 2-clock SoCs?
> 
> The driver will work okay as-is.
> 
> In theory CAN could be broken if renesas,can-clock-select is set to 0x1
> (clkp2) in the DT, as this value will be written to the CAN Clock Select
> Register. However if the documentation is followed there will be no
> problems.
> 
> We should probably update the driver to fix this though, which will be a
> change specific to all RZ/G2 devices, so perhaps we should also be adding
> a "renesas,rzg-gen2-can" family compatible string as well? (to driver and
> documentation)

Yes, I think that sounds reasonable.

But in that case we should pre-emptively not use renesas,rcar-gen3-can for
RZ/G2.