linux-kernel - Re: [PATCH 5/8] iio/counter: add FlexTimer Module Quadrature decoder counter driver

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Message-ID: <CAKKE0ZFs_N+StJ4MQ0peaTy=ADufSVW_tp5zSHsyua2myvMiHQ@mail.gmail.com>
Date:   Mon, 4 Mar 2019 13:36:34 +0100
From:   Patrick Havelange <patrick.havelange@...ensium.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        Esben Haabendal <esben@...bendal.dk>,
        William Breathitt Gray <vilhelm.gray@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pwm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 5/8] iio/counter: add FlexTimer Module Quadrature decoder
 counter driver

On Wed, Feb 20, 2019 at 5:42 PM Jonathan Cameron <jic23@...nel.org> wrote:
[skipped]
> > +
> > +struct ftm_quaddec {
> > +     struct platform_device *pdev;
> > +     void __iomem *ftm_base;
> > +     bool big_endian;
>
> I'm curious. What is the benefit of running in big endian mode?

It is based on the same behaviour as in drivers/clocksource/timer-fsl-ftm.c
The FlexTimer itself on the board I'm testing it with is working in
big endian mode, so this mode is required.

> > +static ssize_t ftm_write_reset(struct iio_dev *indio_dev,
> > +                             uintptr_t private,
> > +                             struct iio_chan_spec const *chan,
> > +                             const char *buf, size_t len)
> > +{
> > +     struct ftm_quaddec *ftm = iio_priv(indio_dev);
> > +
> > +     /* Only "counter reset" is supported for now */
> > +     if (!sysfs_streq(buf, "0")) {
> > +             dev_warn(&ftm->pdev->dev, "Reset only accepts '0'\n");
> > +             return -EINVAL;
>
> Why not just make the channel attribute itself writeable given we are
> setting it to 0?

Good idea, I'll see if this can be applied in the new subsystem.

[skipped]

All other comments are Acked.