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From:   "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Date:   Fri, 4 Sep 2020 18:15:23 +0100
Message-ID: <CA+V-a8uT8d8P8REuXcW9qtCxM84DH+Q4LXZnVTYhT--kswKF=g@mail.gmail.com>
Subject: Re: [PATCH 4/4] ARM: dts: r8a7742-iwg21d-q7: Enable SD2 LED indication
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        Magnus Damm <magnus.damm@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi Geert,

Thank you for the review.

On Thu, Sep 3, 2020 at 1:20 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> On Tue, Aug 25, 2020 at 6:28 PM Lad Prabhakar
> <prabhakar.mahadev-lad.rj@bp.renesas.com> wrote:
> > Add support for LED trigger on SD2 interface.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
>
> > --- a/arch/arm/boot/dts/r8a7742-iwg21d-q7.dts
> > +++ b/arch/arm/boot/dts/r8a7742-iwg21d-q7.dts
> > @@ -63,6 +63,16 @@
> >                 enable-gpios = <&gpio3 11 GPIO_ACTIVE_HIGH>;
> >         };
> >
> > +       leds {
> > +               compatible = "gpio-leds";
> > +
> > +               sdhi2_led {
> > +                       label = "sdio-led";
> > +                       gpios = <&gpio5 22 GPIO_ACTIVE_LOW>;
>
> GPIO_ACTIVE_HIGH?
>
I did try with GPIO_ACTIVE_HIGH and it didn't work as expected. To
make sure I can control the LED through sysfs I deleted the node from
DTS and exported the pin GP5_22 (858) and writing the value "out"
direction and setting the values 0/1 to value did not toggle the SDIO
LED as expected and it stayed OFF all the time.

Looks like there is some information missing in the schematics.

I did some experiments. I completely removed the SDHI, LED and
regulator  nodes and  booted the system and exported GP1_27 (989) and
wrote values 0/1  and this toggled the SDIO_LED.

U-boot sets the below, so in u-boot the SDIO_LED is ON:
    gpio_direction_output(GPIO_GP_1_27, 0); /* power on */
    gpio_set_value(GPIO_GP_1_27, 0);
    gpio_direction_output(GPIO_GP_5_22, 0); /* LED  */
    gpio_set_value(GPIO_GP_5_22, 1);
    gpio_direction_output(GPIO_GP_1_8, 0); /* 1: 3.3V, 0: 1.8V*/
    gpio_set_value(GPIO_GP_1_8, 1);

So in comparison we would need a hog node as below (and with this the
LED triggers correctly as expected),

&gpio5 {
    sdio-led-gpio {
        gpio-hog;
        gpios = <22 GPIO_ACTIVE_HIGH>;
        output-high;
        line-name = "sdio-led-gpio";
    };
};

Let me know if you are OK with the above.

Looks like the SDIO_PWR is tied up with an SDIO_LED pin and the
information is missing from schematics.

Cheers,
Prabhakar

> The LED is driven by an NPN transistor, with the LED between 3.3V and
> the transistor's collector.
>
> > +                       linux,default-trigger = "mmc1";
> > +               };
> > +       };
> > +
> >         lvds-receiver {
> >                 compatible = "ti,ds90cf384a", "lvds-decoder";
> >                 vcc-supply = <&vcc_3v3_tft1>;
>
> With the above fixed:
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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