linux-kernel - Re: [PATCH 2/2] pinctrl: sprd: Add Spreadtrum pin control driver

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Message-ID: <20170531080012.GB31518@spreadtrum.com>
Date:   Wed, 31 May 2017 16:00:12 +0800
From:   Baolin Wang <baolin.wang@...eadtrum.com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Baolin Wang <baolin.wang@...aro.org>
Subject: Re: [PATCH 2/2] pinctrl: sprd: Add Spreadtrum pin control driver

Hi Linus,

On 一,  5月 29, 2017 at 06:28:49下午 +0200, Linus Walleij wrote:
> On Sat, May 27, 2017 at 7:56 AM, Baolin Wang <baolin.wang@...eadtrum.com> wrote:
> 
> > This patch adds the pin control driver for Spreadtrum SC9860 platform.
> >
> > Signed-off-by: Baolin Wang <baolin.wang@...eadtrum.com>
> 
> Overall I see that you want to store functions and groups in the device tree
> using the current helpers from Tony. That is OK if you want to take that
> approach, though I prefer the pins/groups/function encoding in plaintext.
> 
> But when it comes to pin config:
> 
> > +static int sprd_pinconf_get(struct pinctrl_dev *pctldev, unsigned int pin_id,
> > +                           unsigned long *config)
> > +{
> > +       struct sprd_pinctrl *pctl = pinctrl_dev_get_drvdata(pctldev);
> > +       struct sprd_pin *pin = sprd_pinctrl_get_pin_by_id(pctl, pin_id);
> > +
> > +       if (!pin)
> > +               return -EINVAL;
> > +
> > +       if (pin->type == GLOBAL_CTRL_PIN) {
> > +               *config = (readl((void __iomem *)pin->reg) >>
> > +                          pin->bit_offset) & PINCTRL_BIT_MASK(pin->bit_width);
> > +       } else {
> > +               *config = readl((void __iomem *)pin->reg);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> > +static int sprd_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin_id,
> > +                           unsigned long *configs, unsigned int num_configs)
> > +{
> > +       struct sprd_pinctrl *pctl = pinctrl_dev_get_drvdata(pctldev);
> > +       struct sprd_pin *pin = sprd_pinctrl_get_pin_by_id(pctl, pin_id);
> > +       unsigned long reg;
> > +       int i;
> > +
> > +       if (!pin)
> > +               return -EINVAL;
> > +
> > +       for (i = 0; i < num_configs; i++) {
> > +               if (pin->type == GLOBAL_CTRL_PIN) {
> > +                       reg = readl((void __iomem *)pin->reg);
> > +                       reg &= ~(PINCTRL_BIT_MASK(pin->bit_width)
> > +                               << pin->bit_offset);
> > +                       reg |= (configs[i] & PINCTRL_BIT_MASK(pin->bit_width))
> > +                               << pin->bit_offset;
> > +                       writel(reg, (void __iomem *)pin->reg);
> > +               } else {
> > +                       writel(configs[i], (void __iomem *)pin->reg);
> > +               }
> > +               pin->config = configs[i];
> > +       }
> > +
> > +       return 0;
> > +}
> 
> This is just hammering the register values, you have effectively defined your
> register layout as your device tree ABI.
> 
> Please don't do this, please use genric pin config and use the approach
> other drivers take with explicit strings encoding the pin configuration.

Make sense. I will try to use genric pin config instead of the magic number.
Thanks for your comments.

> 
> Even pinctrl-single that maintain quite a bit of muxing data in the device
> tree still use the generic pin config API, see:
> drivers/pinctrl/pinctrl-single.c
> pcs_pinconf_get(), pcs_pinconf_set()
> 
> Same for group config.
> 
> Yours,
> Linus Walleij