linux-kernel - Re: [PATCH 3/3] arm64: dts: renesas: rzg2l-smarc: Enable CANFD

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Date:   Fri, 24 Sep 2021 11:15:44 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH 3/3] arm64: dts: renesas: rzg2l-smarc: Enable CANFD

Hi Geert,

Thank you for the review.

On Fri, Sep 24, 2021 at 10:07 AM Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Wed, Sep 22, 2021 at 11:21 PM Lad Prabhakar
> <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> > Enable CANFD on RZ/G2L SMARC platform.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > Reviewed-by: Biju Das <biju.das.jz@...renesas.com>
>
> Thanks for your patch!
>
> > --- a/arch/arm64/boot/dts/renesas/rzg2l-smarc.dtsi
> > +++ b/arch/arm64/boot/dts/renesas/rzg2l-smarc.dtsi
> > @@ -139,6 +153,32 @@
> >         pinctrl-0 = <&sound_clk_pins>;
> >         pinctrl-names = "default";
> >
> > +       can0_pins: can0 {
> > +               pinmux = <RZG2L_PORT_PINMUX(10, 1, 2)>, /* TX */
> > +                        <RZG2L_PORT_PINMUX(11, 0, 2)>; /* RX */
> > +       };
> > +
> > +       /* SW7 should be at position 2->3 so that GPIO8_CAN0_STB line is activated */
> > +       can0-stb {
> > +               gpio-hog;
> > +               gpios = <RZG2L_GPIO(42, 2) GPIO_ACTIVE_LOW>;
> > +               output-high;
>
> While this drives the STB signal correctly, I find it confusing.
> According to the datasheet, the STB signal is active-high, so it has to
> be pulled low to disable standby.
agreed.

> So to reflect the meaning of the STB line, I would write:
>
>         gpios = <RZG2L_GPIO(42, 2) GPIO_ACTIVE_HIGH>;
>         output-low;
>
will re-spin the patch 3/3 as above.

Cheers,
Prabhakar

> > +               line-name = "can0_stb";
> > +       };
> > +
> > +       can1_pins: can1 {
> > +               pinmux = <RZG2L_PORT_PINMUX(12, 1, 2)>, /* TX */
> > +                        <RZG2L_PORT_PINMUX(13, 0, 2)>; /* RX */
> > +       };
> > +
> > +       /* SW8 should be at position 2->3 so that GPIO9_CAN1_STB line is activated */
> > +       can1-stb {
> > +               gpio-hog;
> > +               gpios = <RZG2L_GPIO(42, 3) GPIO_ACTIVE_LOW>;
> > +               output-high;
>
> Likewise.
>
> > +               line-name = "can1_stb";
> > +       };
> > +
>
> The rest looks good to me, so with the above fixed:
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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