linux-kernel - Re: [PATCH V2 2/3] gpio: xilinx: Add interrupt support

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Message-ID: <CAHp75Vd7BU5DYqyQFGfBtKrb6jWFEQjMCu2MOa_7M8XYkt6BFA@mail.gmail.com>
Date:   Thu, 23 Jul 2020 21:03:14 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Srinivas Neeli <srinivas.neeli@...inx.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Michal Simek <michal.simek@...inx.com>,
        shubhrajyoti.datta@...inx.com, sgoud@...inx.com,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        git@...inx.com
Subject: Re: [PATCH V2 2/3] gpio: xilinx: Add interrupt support

On Thu, Jul 23, 2020 at 5:08 PM Srinivas Neeli
<srinivas.neeli@...inx.com> wrote:
>
> Adds interrupt support to the Xilinx GPIO driver so that rising and
> falling edge line events can be supported. Since interrupt support is
> an optional feature in the Xilinx IP, the driver continues to support
> devices which have no interrupt provided.

...

> +#include <linux/irqchip/chained_irq.h>

Not sure I see a user of it.

...

> +/**
> + * xgpio_xlate - Translate gpio_spec to the GPIO number and flags
> + * @gc: Pointer to gpio_chip device structure.
> + * @gpiospec:  gpio specifier as found in the device tree
> + * @flags: A flags pointer based on binding
> + *
> + * Return:
> + * irq number otherwise -EINVAL
> + */
> +static int xgpio_xlate(struct gpio_chip *gc,
> +                      const struct of_phandle_args *gpiospec, u32 *flags)
> +{
> +       if (gc->of_gpio_n_cells < 2) {
> +               WARN_ON(1);
> +               return -EINVAL;
> +       }
> +
> +       if (WARN_ON(gpiospec->args_count < gc->of_gpio_n_cells))
> +               return -EINVAL;
> +
> +       if (gpiospec->args[0] >= gc->ngpio)
> +               return -EINVAL;
> +
> +       if (flags)
> +               *flags = gpiospec->args[1];
> +
> +       return gpiospec->args[0];
> +}

This looks like a very standart xlate function for GPIO. Why do you
need to open-code it?

...

> +/**
> + * xgpio_irq_ack - Acknowledge a child GPIO interrupt.

> + * This currently does nothing, but irq_ack is unconditionally called by
> + * handle_edge_irq and therefore must be defined.

This should go after parameter description(s).

> + * @irq_data: per irq and chip data passed down to chip functions
> + */

...

>  /**
> + * xgpio_irq_mask - Write the specified signal of the GPIO device.
> + * @irq_data: per irq and chip data passed down to chip functions

In all comments irq -> IRQ.

> + */
> +static void xgpio_irq_mask(struct irq_data *irq_data)
> +{
> +       unsigned long flags;
> +       struct xgpio_instance *chip = irq_data_get_irq_chip_data(irq_data);
> +       int irq_offset = irqd_to_hwirq(irq_data);
> +       int index = xgpio_index(chip, irq_offset);
> +       int offset = xgpio_offset(chip, irq_offset);
> +
> +       spin_lock_irqsave(&chip->gpio_lock, flags);
> +

> +       chip->irq_enable[index] &= ~BIT(offset);

If you convert your data structure to use bitmaps (and respective API) like

#define XILINX_NGPIOS  64
...
  DECLARE_BITMAP(irq_enable, XILINX_NGPIOS);
...

it will make code better to read and understand. For example, here it
will be just
__clear_bit(offset, chip->irq_enable);

> +       dev_dbg(chip->gc.parent, "Disable %d irq, irq_enable_mask 0x%x\n",
> +               irq_offset, chip->irq_enable[index]);

Under spin lock?! Hmm...

> +       if (!chip->irq_enable[index]) {
> +               /* Disable per channel interrupt */
> +               u32 temp = xgpio_readreg(chip->regs + XGPIO_IPIER_OFFSET);
> +
> +               temp &= ~BIT(index);
> +               xgpio_writereg(chip->regs + XGPIO_IPIER_OFFSET, temp);
> +       }
> +       spin_unlock_irqrestore(&chip->gpio_lock, flags);
> +}

...

> +       for (index = 0; index < num_channels; index++) {
> +               if ((status & BIT(index))) {

If gpio_width is the same among banks, you can use for_each_set_bit()
here as well.

...

> +                       for_each_set_bit(bit, &all_events, 32) {
> +                               generic_handle_irq(irq_find_mapping
> +                                       (chip->gc.irq.domain, offset + bit));

Strange indentation. Maybe a temporary variable helps?

...

> +       chip->irq = platform_get_irq_optional(pdev, 0);
> +       if (chip->irq <= 0) {
> +               dev_info(&pdev->dev, "GPIO IRQ not set\n");

Why do you need an optional variant if you print an error anyway?

> +       } else {


...

> +               chip->gc.irq.parents = (unsigned int *)&chip->irq;
> +               chip->gc.irq.num_parents = 1;

Current pattern is to use devm_kcalloc() for it (Linus has plans to
simplify this in the future and this will help him to find what
patterns are being used)

-- 
With Best Regards,
Andy Shevchenko