linux-kernel - Re: [RESEND PATCH v3 2/3] pinctrl: pinctrl-mchp-sgpio: Add pinctrl driver for Microsemi Serial GPIO

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Message-ID: <CACRpkdYqKqqM8D0vrBWbo0=7OFthU2kcK2tjd45dD7DxEkaYWg@mail.gmail.com>
Date:   Fri, 9 Oct 2020 11:38:32 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Lars Povlsen <lars.povlsen@...rochip.com>
Cc:     Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Subject: Re: [RESEND PATCH v3 2/3] pinctrl: pinctrl-mchp-sgpio: Add pinctrl
 driver for Microsemi Serial GPIO

Hi Lars,

I'm overall mostly happy with the latest posting (not the one I respond to here)

On Thu, Oct 8, 2020 at 12:57 PM Lars Povlsen <lars.povlsen@...rochip.com> wrote:
> > On Tue, Oct 6, 2020 at 4:25 PM Lars Povlsen <lars.povlsen@...rochip.com> wrote:

> >> +       gc->of_xlate            = microchip_sgpio_of_xlate;
> >> +       gc->of_gpio_n_cells     = 3;
> >
> > So I'm sceptical to this.
> >
> > Why can't you just use the pin index in cell 0 directly
> > and avoid cell 1?
> >
>
> You scepticism has surfaced before :-). The (now) 2 indices relates to
> how the hardware address signals.
>
> Each signal/pin is addressed by port, bit number and direction. We now
> have the direction encoded in the bank/phandle.

I'm sorry but I just don't get it, I suppose. To me it is pretty
straight-forward
that the cells indicate the pin and then the flags. I do understand you
need the port at all, since this is implicit from the reg property
of the DT node. Are these two different things?

Yours,
Linus Walleij