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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 18 Mar 2021 14:15:50 +0200
Message-ID: <CAHp75VdYeVOHu5T37EBEjL5xfgjevzb-ErZb2QMy7defXDS5fg@mail.gmail.com>
Subject: Re: [PATCH v3 3/3] pinctrl: pinctrl-single: fix pcs_pin_dbg_show()
 when bits_per_mux is not zero
To:     Hanna Hawa <hhhawa@amazon.com>
Cc:     Tony Lindgren <tony@atomide.com>,
        Haojian Zhuang <haojian.zhuang@linaro.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        David Woodhouse <dwmw@amazon.co.uk>, benh@amazon.com,
        ronenk@amazon.com, talel@amazon.com, jonnyc@amazon.com,
        hanochu@amazon.com, tgershi@amazon.com,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        Linux OMAP Mailing List <linux-omap@vger.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Precedence: bulk

On Wed, Mar 17, 2021 at 11:42 PM Hanna Hawa <hhhawa@amazon.com> wrote:
>

> An SError was detected when trying to print the supported pins in a

What is SError? Yes, I have read a discussion, but here is the hint:
if a person sees this as a first text due to, for example, bisecting
an issue, what she/he can get from this cryptic name?

> pinctrl device which supports multiple pins per register. This change
> fixes the pcs_pin_dbg_show() in pinctrl-single driver when bits_per_mux
> is not zero. In addition move offset calculation and pin offset in
> register to common function.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> Fixes: 4e7e8017a80e ("pinctrl: pinctrl-single: enhance to configure multiple pins of different modules")
> Signed-off-by: Hanna Hawa <hhhawa@amazon.com>
> ---
>  drivers/pinctrl/pinctrl-single.c | 57 +++++++++++++++++++++-----------
>  1 file changed, 37 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
> index f3394517cb2e..4595acf6545e 100644
> --- a/drivers/pinctrl/pinctrl-single.c
> +++ b/drivers/pinctrl/pinctrl-single.c
> @@ -270,20 +270,46 @@ static void __maybe_unused pcs_writel(unsigned val, void __iomem *reg)
>         writel(val, reg);
>  }
>
> +static unsigned int pcs_pin_reg_offset_get(struct pcs_device *pcs,
> +                                          unsigned int pin)
> +{

> +       unsigned int mux_bytes;
> +
> +       mux_bytes = pcs->width / BITS_PER_BYTE;

Can be folded to one line.

> +       if (pcs->bits_per_mux) {
> +               unsigned int pin_offset_bytes;
> +
> +               pin_offset_bytes = (pcs->bits_per_pin * pin) / BITS_PER_BYTE;
> +               return (pin_offset_bytes / mux_bytes) * mux_bytes;

Side note for the further improvements (in a separate change, because
I see that you just copied an original code, and after all this is
just a fix patch): this can be replaced by round down APIs (one which
works for arbitrary divisors).

> +       }
> +
> +       return pin * mux_bytes;
> +}
> +
> +static unsigned int pcs_pin_shift_reg_get(struct pcs_device *pcs,
> +                                         unsigned int pin)
> +{
> +       return (pin % (pcs->width / pcs->bits_per_pin)) * pcs->bits_per_pin;

Also a side note: I'm wondering if this can be optimized to have less divisions.

> +}
> +
>  static void pcs_pin_dbg_show(struct pinctrl_dev *pctldev,
>                                         struct seq_file *s,
>                                         unsigned pin)
>  {
>         struct pcs_device *pcs;
> -       unsigned val, mux_bytes;
> +       unsigned int val;
>         unsigned long offset;
>         size_t pa;
>
>         pcs = pinctrl_dev_get_drvdata(pctldev);
>
> -       mux_bytes = pcs->width / BITS_PER_BYTE;
> -       offset = pin * mux_bytes;
> +       offset = pcs_pin_reg_offset_get(pcs, pin);
>         val = pcs->read(pcs->base + offset);
> +
> +       if (pcs->bits_per_mux)
> +               val &= pcs->fmask << pcs_pin_shift_reg_get(pcs, pin);
> +
>         pa = pcs->res->start + offset;
>
>         seq_printf(s, "%zx %08x %s ", pa, val, DRIVER_NAME);
> @@ -384,7 +410,6 @@ static int pcs_request_gpio(struct pinctrl_dev *pctldev,
>         struct pcs_device *pcs = pinctrl_dev_get_drvdata(pctldev);
>         struct pcs_gpiofunc_range *frange = NULL;
>         struct list_head *pos, *tmp;
> -       int mux_bytes = 0;
>         unsigned data;
>
>         /* If function mask is null, return directly. */
> @@ -392,29 +417,27 @@ static int pcs_request_gpio(struct pinctrl_dev *pctldev,
>                 return -ENOTSUPP;
>
>         list_for_each_safe(pos, tmp, &pcs->gpiofuncs) {
> +               u32 offset;
> +
>                 frange = list_entry(pos, struct pcs_gpiofunc_range, node);
>                 if (pin >= frange->offset + frange->npins
>                         || pin < frange->offset)
>                         continue;
> -               mux_bytes = pcs->width / BITS_PER_BYTE;
>
> -               if (pcs->bits_per_mux) {
> -                       int byte_num, offset, pin_shift;
> +               offset = pcs_pin_reg_offset_get(pcs, pin);
>
> -                       byte_num = (pcs->bits_per_pin * pin) / BITS_PER_BYTE;
> -                       offset = (byte_num / mux_bytes) * mux_bytes;
> -                       pin_shift = pin % (pcs->width / pcs->bits_per_pin) *
> -                                   pcs->bits_per_pin;
> +               if (pcs->bits_per_mux) {
> +                       int pin_shift = pcs_pin_shift_reg_get(pcs, pin);
>
>                         data = pcs->read(pcs->base + offset);
>                         data &= ~(pcs->fmask << pin_shift);
>                         data |= frange->gpiofunc << pin_shift;
>                         pcs->write(data, pcs->base + offset);
>                 } else {
> -                       data = pcs->read(pcs->base + pin * mux_bytes);
> +                       data = pcs->read(pcs->base + offset);
>                         data &= ~pcs->fmask;
>                         data |= frange->gpiofunc;
> -                       pcs->write(data, pcs->base + pin * mux_bytes);
> +                       pcs->write(data, pcs->base + offset);
>                 }
>                 break;
>         }
> @@ -724,14 +747,8 @@ static int pcs_allocate_pin_table(struct pcs_device *pcs)
>         for (i = 0; i < pcs->desc.npins; i++) {
>                 unsigned offset;
>                 int res;
> -               int byte_num;
>
> -               if (pcs->bits_per_mux) {
> -                       byte_num = (pcs->bits_per_pin * i) / BITS_PER_BYTE;
> -                       offset = (byte_num / mux_bytes) * mux_bytes;
> -               } else {
> -                       offset = i * mux_bytes;
> -               }
> +               offset = pcs_pin_reg_offset_get(pcs, i);
>                 res = pcs_add_pin(pcs, offset);
>                 if (res < 0) {
>                         dev_err(pcs->dev, "error adding pins: %i\n", res);
> --
> 2.17.1
>


-- 
With Best Regards,
Andy Shevchenko