linux-kernel - Re: [PATCH 11/14] arm64: renesas: rzg3s-smarc-som: Invert the logic for SW_SD2

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Date:   Wed, 6 Dec 2023 11:56:48 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Claudiu <claudiu.beznea@...on.dev>
Cc:     s.shtylyov@....ru, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        linux@...linux.org.uk, geert+renesas@...der.be,
        magnus.damm@...il.com, mturquette@...libre.com, sboyd@...nel.org,
        linus.walleij@...aro.org, p.zabel@...gutronix.de, arnd@...db.de,
        m.szyprowski@...sung.com, alexandre.torgue@...s.st.com, afd@...com,
        broonie@...nel.org, alexander.stein@...tq-group.com,
        eugen.hristev@...labora.com, sergei.shtylyov@...il.com,
        prabhakar.mahadev-lad.rj@...renesas.com,
        biju.das.jz@...renesas.com, linux-renesas-soc@...r.kernel.org,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-gpio@...r.kernel.org,
        Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 11/14] arm64: renesas: rzg3s-smarc-som: Invert the logic
 for SW_SD2_EN macro

On Wed, Dec 6, 2023 at 11:33 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Mon, Nov 20, 2023 at 8:03 AM Claudiu <claudiu.beznea@...on.dev> wrote:
> > From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >
> > The intention of SW_SD2_EN macro was to reflect the state of SW_CONFIG3
> > switch available on RZ/G3S Smarc Module. According to documentation SD2
> > is enabled when switch is in OFF state. For this, changed the logic of
> > marco to map value 0 to switch's OFF state and value 1 to switch's ON
> > state. Along with this update the description for each state for better
> > understanding.
> >
> > The value of SW_SD2_EN macro was not changed in file because, according to
> > documentation, the default state for this switch is ON.
> >
> > Fixes: adb4f0c5699c ("arm64: dts: renesas: Add initial support for RZ/G3S SMARC SoM")
> > Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>
> Thanks for your patch!
>
> > --- a/arch/arm64/boot/dts/renesas/rzg3s-smarc-som.dtsi
> > +++ b/arch/arm64/boot/dts/renesas/rzg3s-smarc-som.dtsi
> > @@ -14,8 +14,8 @@
> >   *     0 - SD0 is connected to eMMC
> >   *     1 - SD0 is connected to uSD0 card
> >   * @SW_SD2_EN:
> > - *     0 - SCIF1, SSI0, IRQ0, IRQ1 connected to SoC
> > - *     1 - SD2 is connected to SoC
> > + *     0 - (switch OFF) SD2 is connected to SoC
> > + *     1 - (switch ON)  SCIF1, SSI0, IRQ0, IRQ1 connected to SoC
>
> I think this is still confusing: SW_SD2_EN refers to an active-low signal
> (SW_SD2_EN#) in the schematics.

OMG, while the signal is called "SW_SD2_EN#" in the schematics, it is
_not_ active-low!
SW_D2_EN# drives a STG3692 quad SPDT switch, and SD2 is enabled
if SW_D2_EN# is high...

The RZ/G3S SMARC Module User Manual says:

Signal SW_SD2_EN ON: SD2 is disabled.
Signal SW_SD2_EN OFF: SD2 is enabled.

So whatever we do, something will look odd :-(

> Before, SW_SD2_EN used assertion-logic (1 is enabled), and didn't
> match the physical signal level.
> After your patch, SW_SD2_EN matches the active-low physical level, but
> this is not reflected in the name...
>
> >   */
> >  #define SW_SD0_DEV_SEL 1
> >  #define SW_SD2_EN      1
> > @@ -25,7 +25,7 @@ / {
> >
> >         aliases {
> >                 mmc0 = &sdhi0;
> > -#if SW_SD2_EN
> > +#if !SW_SD2_EN
>
> ... so this condition looks really weird.

Still, I think the original looks nicer here.

So I suggest to keep the original logic, but clarify the position of
the switch.
Does that make sense?


>
> >                 mmc2 = &sdhi2;
> >  #endif
> >         };
> > @@ -116,7 +116,7 @@ &sdhi0 {
> >  };
> >  #endif
> >
> > -#if SW_SD2_EN
> > +#if !SW_SD2_EN
> >  &sdhi2 {
> >         pinctrl-0 = <&sdhi2_pins>;
> >         pinctrl-names = "default";
>
> So I think SW_SD2_EN should be renamed to SW_SD2_EN_N.
>
> Cfr. SW_ET0_EN_N on RZ/G2UL:
>
> arch/arm64/boot/dts/renesas/r9a07g043u11-smarc.dts- * DIP-Switch SW1 setting
> arch/arm64/boot/dts/renesas/r9a07g043u11-smarc.dts- * 1 : High; 0: Low
> arch/arm64/boot/dts/renesas/r9a07g043u11-smarc.dts- * SW1-2 :
> SW_SD0_DEV_SEL    (0: uSD; 1: eMMC)
> arch/arm64/boot/dts/renesas/r9a07g043u11-smarc.dts- * SW1-3 :
> SW_ET0_EN_N               (0: ETHER0; 1: CAN0, CAN1, SSI1, RSPI1)
> arch/arm64/boot/dts/renesas/r9a07g043u11-smarc.dts- * Please change
> below macros according to SW1 setting on the SoM

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