linux-kernel - Re: [PATCH v6 7/9] gpio: Add gpio driver for Actions OWL S900 SoC

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Date:   Sat, 31 Mar 2018 00:04:11 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        刘炜 <liuwei@...ions-semi.com>,
        mp-cs@...ions-semi.com, 96boards@...obotics.com,
        devicetree <devicetree@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        amit.kucheria@...aro.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        hzhang@...obotics.com, bdong@...obotics.com,
        Mani Sadhasivam <manivannanece23@...il.com>
Subject: Re: [PATCH v6 7/9] gpio: Add gpio driver for Actions OWL S900 SoC

On Wed, Mar 28, 2018 at 8:47 PM, Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> Add gpio driver for Actions Semi OWL family S900 SoC. Set of registers
> controlling the gpio shares the same register range with pinctrl block.
>
> GPIO registers are organized as 6 banks and each bank controls the
> maximum of 32 gpios.
>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> +static void owl_gpio_update_reg(void __iomem *base, unsigned int pin, int flag)
> +{
> +       u32 val;
> +
> +       val = readl_relaxed(base);
> +
> +       if (flag)
> +               val |= BIT(pin);
> +       else
> +               val &= ~BIT(pin);
> +
> +       writel_relaxed(val, base);
> +}

Hmm... Just realized that this driver misses locking.

Something like
owl_gpio_update_reg_locked()
{
 spin_lock();
 owl_gpio_update_reg();
 spin_unlock();
}

> +
> +static int owl_gpio_request(struct gpio_chip *chip, unsigned int offset)
> +{
> +       struct owl_gpio *gpio = gpiochip_get_data(chip);
> +
> +       /*
> +        * GPIOs have higher priority over other modules, so either setting
> +        * them as OUT or IN is sufficient
> +        */
> +       owl_gpio_update_reg(gpio->base + GPIO_OUTEN, offset, true);

...to use in such cases.

> +
> +       return 0;
> +}
> +
> +static void owl_gpio_free(struct gpio_chip *chip, unsigned int offset)
> +{
> +       struct owl_gpio *gpio = gpiochip_get_data(chip);
> +
> +       /* disable gpio output */
> +       owl_gpio_update_reg(gpio->base + GPIO_OUTEN, offset, false);
> +
> +       /* disable gpio input */
> +       owl_gpio_update_reg(gpio->base + GPIO_INEN, offset, false);

...or

spin_lock();
owl_gpio_update_reg();
owl_gpio_update_reg();
spin_unlock();

...in this and similar cases.

> +}


-- 
With Best Regards,
Andy Shevchenko