linux-kernel - Re: [PATCH 1/4] arm64: dts: beacon-renesom: Fix gpio expander reference

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Date:   Fri, 13 Jan 2023 15:25:45 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Adam Ford <aford173@...il.com>
Cc:     linux-renesas-soc@...r.kernel.org, aford@...conembedded.com,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] arm64: dts: beacon-renesom: Fix gpio expander reference

Hi Adam,

On Fri, Jan 13, 2023 at 2:17 PM Adam Ford <aford173@...il.com> wrote:
> On Wed, Jan 11, 2023 at 11:05 AM Adam Ford <aford173@...il.com> wrote:
> > On Wed, Jan 11, 2023 at 10:29 AM Geert Uytterhoeven
> > <geert@...ux-m68k.org> wrote:
> > > On Wed, Jan 4, 2023 at 3:12 PM Adam Ford <aford173@...il.com> wrote:
> > > > The board used to originally introduce the Beacon Embedded
> > > > RZ/G2[M/N/H] boards had a GPIO expander with address 20, but
> > > > this was change when the final board went to production.
> > > >
> > > > The production boards changed both the part itself and
> > > > the address.  With the incorrect address, the LCD cannot
> > > > come up.  If the LCD fails, the rcar-du driver fails to come up,
> > > > and that also breaks HDMI.
> > > >
> > > > Pre-release board were not shipped to the general public, so it
> > > > should be safe to push this as a fix.  Anyone with a production
> > > > board would have video fail due to this GPIO expander change.
> > > >
> > > > Fixes: a1d8a344f1ca ("arm64: dts: renesas: Introduce r8a774a1-beacon-rzg2m-kit")
> > > > Signed-off-by: Adam Ford <aford173@...il.com>

> > > > --- a/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi
> > > > +++ b/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi
> > > > @@ -437,20 +437,6 @@ wm8962_endpoint: endpoint {
> > > >                 };
> > > >         };
> > > >
> > > > -       /* 0 - lcd_reset */
> > > > -       /* 1 - lcd_pwr */
> > > > -       /* 2 - lcd_select */
> > > > -       /* 3 - backlight-enable */
> > > > -       /* 4 - Touch_shdwn */
> > > > -       /* 5 - LCD_H_pol */
> > > > -       /* 6 - lcd_V_pol */
> > > > -       gpio_exp1: gpio@20 {
> > > > -               compatible = "onnn,pca9654";
> > > > -               reg = <0x20>;
> > > > -               gpio-controller;
> > > > -               #gpio-cells = <2>;
> > > > -       };
> > > > -
> > > >         touchscreen@26 {
> > > >                 compatible = "ilitek,ili2117";
> > > >                 reg = <0x26>;
> > > > @@ -482,6 +468,21 @@ hd3ss3220_out_ep: endpoint {
> > > >                         };
> > > >                 };
> > > >         };
> > > > +
> > > > +       gpio_exp1: gpio@70 {
> > > > +               compatible = "onnn,pca9654";
> > >
> > > According to the patch description, the actual part was changed, too?
>
> After a bit of some investigation, the part was changed to
> nxp,pca9538.  It appears to be the same driver and the same ".data"
> structure is used.  This probably explains why I didn't see any issues
> when I was testing this.  Unfortunately, the hardware engineer who
> made this hardware change is not around to ask why the change was
> made.

Yeah, there are lots of compatible parts.

> I'll do a V2 since, I don't see this in renesas-devel.

Correct, I was waiting for clarification.
Looking forward to v2...

Thanks!

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