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

[Robert Hancock]

On 2020-07-23 12:03 p.m., Andy Shevchenko wrote:
> > +/**
> > + * 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?

Indeed, this seems the same as the of_gpio_simple_xlate callback which 
is used if no xlate callback is specified, so I'm not sure why this is 
necessary?

> ...
>
> > +/**
> > + * 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)

--
Robert Hancock
Senior Hardware Designer
SED Systems, a division of Calian Ltd.
Email: hancock@xxxxxxxxxxxxx