Re: [PATCH 10/16] gpio: add driver for Atheros AR2315 SoC GPIO controller

[Linus Walleij <linus.walleij@xxxxxxxxxx>]

On Sun, Sep 28, 2014 at 8:33 PM, Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx> wrote:

> Atheros AR2315 SoC have a builtin GPIO controller, which could be
> accessed via memory mapped registers. This patch adds new driver
> for them.
>
> Signed-off-by: Sergey Ryazanov <ryazanov.s.a@xxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Alexandre Courbot <gnurou@xxxxxxxxx>
> Cc: linux-gpio@xxxxxxxxxxxxxxx

> +config GPIO_AR2315
> +       bool "AR2315 SoC GPIO support"
> +       default y if SOC_AR2315
> +       depends on SOC_AR2315
> +       help
> +         Say yes here to enable GPIO support for Atheros AR2315+ SoCs.

select GPIOLIB_IRQCHIP

As far as I can see this driver should use the gpiolib irqchip helpers
and create a cascading irqchip. The code uses some copy/pasting
from earlier drivers which is not a good idea. Look at one of the drivers
using GPIOLIB_IRQCHIP and be inspired, check e.g. gpio-pl061.c
or gpio-zynq.c

> +static u32 ar2315_gpio_intmask;
> +static u32 ar2315_gpio_intval;
> +static unsigned ar2315_gpio_irq_base;
> +static void __iomem *ar2315_mem;

No static locals. Allocate and use a state container, see
Documentation/driver-model/design-patterns.txt

> +static inline u32 ar2315_gpio_reg_read(unsigned reg)
> +{
> +       return __raw_readl(ar2315_mem + reg);
> +}

Use readl_relaxed() instead.

> +static inline void ar2315_gpio_reg_write(unsigned reg, u32 val)
> +{
> +       __raw_writel(val, ar2315_mem + reg);
> +}

Use writel_relaxed() instead.

When you use the state container, you need to do a
state dereference like that:

mystate->base + reg

So I don't think these inlines buy you anything. Just use
readl/writel_relaxed directly in the code.

> +static inline void ar2315_gpio_reg_mask(unsigned reg, u32 mask, u32 val)
> +{
> +       ar2315_gpio_reg_write(reg, (ar2315_gpio_reg_read(reg) & ~mask) | val);
> +}

Too simple helper IMO, if you wanna do this in some organized fashion,
use regmap.

> +static void ar2315_gpio_int_setup(unsigned gpio, int trig)
> +{
> +       u32 reg = ar2315_gpio_reg_read(AR2315_GPIO_INT);
> +
> +       reg &= ~(AR2315_GPIO_INT_NUM_M | AR2315_GPIO_INT_TRIG_M);
> +       reg |= gpio | AR2315_GPIO_INT_TRIG(trig);
> +       ar2315_gpio_reg_write(AR2315_GPIO_INT, reg);
> +}

Trig? Isn't this supposed to be done in the .set_type()
callback?

> +static void ar2315_gpio_irq_unmask(struct irq_data *d)
> +{
> +       unsigned gpio = d->irq - ar2315_gpio_irq_base;

This kind of weird calculations go away with irqdomain and that
is in turn used by GPIOLIB_IRQCHIP.

After that you will just use d->hwirq. And name the variable
"offset" while you're at it.

> +       u32 dir = ar2315_gpio_reg_read(AR2315_GPIO_DIR);
> +
> +       /* Enable interrupt with edge detection */
> +       if ((dir & AR2315_GPIO_DIR_M(gpio)) != AR2315_GPIO_DIR_I(gpio))
> +               return;
> +
> +       ar2315_gpio_intmask |= (1 << gpio);

#include <linux/bitops.h>

ar2315_gpio_intmask |= BIT(gpio);

> +       ar2315_gpio_int_setup(gpio, AR2315_GPIO_INT_TRIG_EDGE);
> +}

> +static struct irq_chip ar2315_gpio_irq_chip = {
> +       .name           = DRIVER_NAME,
> +       .irq_unmask     = ar2315_gpio_irq_unmask,
> +       .irq_mask       = ar2315_gpio_irq_mask,
> +};

So why is .set_type() not implemented and instead hard-coded into
the unmask function? Please fix this. It will be called by the
core eventually no matter what.

> +static void ar2315_gpio_irq_init(unsigned irq)
> +{
> +       unsigned i;
> +
> +       ar2315_gpio_intval = ar2315_gpio_reg_read(AR2315_GPIO_DI);
> +       for (i = 0; i < AR2315_GPIO_NUM; i++) {
> +               unsigned _irq = ar2315_gpio_irq_base + i;
> +
> +               irq_set_chip_and_handler(_irq, &ar2315_gpio_irq_chip,
> +                                        handle_level_irq);
> +       }
> +       irq_set_chained_handler(irq, ar2315_gpio_irq_handler);
> +}

No, use the gpiolib irqchip helpers.

> +static int ar2315_gpio_get_val(struct gpio_chip *chip, unsigned gpio)
> +{
> +       return (ar2315_gpio_reg_read(AR2315_GPIO_DI) >> gpio) & 1;
> +}

Do this instead:

return !!(ar2315_gpio_reg_read(AR2315_GPIO_DI) & BIT(offset));

> +static int ar2315_gpio_to_irq(struct gpio_chip *chip, unsigned gpio)
> +{
> +       return ar2315_gpio_irq_base + gpio;
> +}

You do not implement this at all when using the gpiolib irqchip helpers.

> +static int ar2315_gpio_probe(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct resource *res;
> +       unsigned irq;
> +       int ret;
> +
> +       if (ar2315_mem)
> +               return -EBUSY;
> +
> +       res = platform_get_resource_byname(pdev, IORESOURCE_IRQ, DRIVER_NAME);
> +       if (!res) {
> +               dev_err(dev, "not found IRQ number\n");
> +               return -ENXIO;
> +       }
> +       irq = res->start;

Use

irq = platform_get_irq_byname(pdev, DRIVER_NAME);
if (irq < 0)...

> +       ret = irq_alloc_descs(-1, 0, AR2315_GPIO_NUM, 0);
> +       if (ret < 0) {
> +               dev_err(dev, "failed to allocate IRQ numbers\n");
> +               return ret;
> +       }
> +       ar2315_gpio_irq_base = ret;
> +
> +       ar2315_gpio_irq_init(irq);

No, let GPIOLIB_IRQCHIP handle this.

> +static int __init ar2315_gpio_init(void)
> +{
> +       return platform_driver_register(&ar2315_gpio_driver);
> +}
> +subsys_initcall(ar2315_gpio_init);

Why are you using subsys_initcall()?

This should not be necessary.

Yours,
Linus Walleij
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