linux-kernel - Re: [PATCH] arm64: dts: renesas: ulcb-kf: add 9-asix sensor device

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Message-ID: <CAMuHMdWWu=be9pxh3QQSy-xnFjOs60JZt9mr-Q=rkQnBKFKMjQ@mail.gmail.com>
Date:   Wed, 26 Jan 2022 16:35:14 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Nikita Yushchenko <nikita.yoush@...entembedded.com>
Cc:     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>
Subject: Re: [PATCH] arm64: dts: renesas: ulcb-kf: add 9-asix sensor device

Hi Nikita,

On Wed, Jan 26, 2022 at 4:28 PM Nikita Yushchenko
<nikita.yoush@...entembedded.com> wrote:
> >> Interrupt definition is not added yet, because the interrupt lines of
> >> lsm9ds0 are pulled to VCC on the board, which implies need for
> >> active-low configuration. But st_sensors drivers currently can't work
> >> with active-low interrupts on this chip.
> >
> > That's unfortunate, as DT describes hardware, not limitations of the
> > software stack.
>
> Unfortunately, if interrupt definition is added, driver does wrong things and causes board hang.

OK.

> >> +                               vdd-supply = <&accel_3v3>;
> >> +                               vddio-supply = <&accel_3v3>;
> >
> > According to the bindings, the supplies are not required, so you can
> > leave them out? Or are the bindings wrong?
>
> If supplies are not defined, warning messages about dummy regulator are logged.

OK.

> > (The bindings also say "interrupts: maxItems 2", while the "interrupts:
> >   description" says up to three interrupts, doh...)
>
> Chip has 3 interrupt outputs. On KF board, all those are ANDed together and result connected to SoC's
> gpio that is expected to be used as a shared active-low interrupt. Driver currently claims that this
> chip does not support active-low interrupts. Per datasheet, this is not true. But driver's way to set up
> interrupt registers does not scale to the case when interrupts have to be configured by different bits
> in several registers, that part of the driver has to be somehow rewritten. I guess nobody has ever tried
> to make these drivers (st_*) to drive a compound device (accel+gyro) with interrupts.
>
> At the same time, the device is perfectly useful without interrupts, and that is how it is enabled in
> the vendor BSP.

OK, will queue in renesas-devel for v5.18, with the low-hanging fruits
(node names, order) fixed.

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