linux-kernel - Re: [PATCH] pinctrl: cherryview: Add quirk with custom translation of ACPI GPIO numbers

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Date:   Sat, 8 Feb 2020 19:43:24 +0100
From:   Michał Stanek <mst@...ihalf.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     linux-gpio@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, stanekm@...gle.com,
        stable@...r.kernel.org, Marcin Wojtas <mw@...ihalf.com>,
        levinale@...omium.org, andriy.shevchenko@...ux.intel.com,
        Linus Walleij <linus.walleij@...aro.org>,
        bgolaszewski@...libre.com, rafael.j.wysocki@...el.com,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [PATCH] pinctrl: cherryview: Add quirk with custom translation of
 ACPI GPIO numbers

> >
> > Hi Mika,
> >
> > The previous patches from Dmitry handled IRQ numbering, here we have a
> > similar issue with GPIO to pin translation - hardcoded values in FW
> > which do not agree with the (non-consecutive) numbering in newer
> > kernels.
>
> Hmm, so instead of passing GpioIo/GpioInt resources to devices the
> firmware uses some hard-coded Linux GPIO numbering scheme? Would you
> able to share the exact firmware description where this happens?

Actually it is a GPIO offset in ACPI tables for Braswell that was
hardcoded in the old firmware to match the previous (consecutive)
Linux GPIO numbering.

> > > What GPIO(s) we are talking about and how does it show up to the user?
> >
> > As an example, the issue manifests itself when you run 'crossystem
> > wpsw_cur'. On my Kefka it incorrectly reports the value as 1 instead
> > of 0 when the write protect screw is removed.
>
> Is it poking GPIOs directly through sysfs relying the Linux GPIO
> numbering (which can change and is fragile anyway)?

I believe so, yes.