linux-kernel - Re: [PATCH v2 3/5] gpio: msc313: MStar MSC313 GPIO driver

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Date:   Thu, 5 Nov 2020 10:40:21 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Daniel Palmer <daniel@...f.com>, Marc Zyngier <maz@...nel.org>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, arm-kernel@...ts.infradead.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] gpio: msc313: MStar MSC313 GPIO driver

On Mon, Oct 19, 2020 at 4:10 PM Daniel Palmer <daniel@...f.com> wrote:

> This adds a driver that supports the GPIO block found in
> MStar/SigmaStar ARMv7 SoCs.
>
> The controller seems to support 128 lines but where they
> are wired up differs between chips and no currently known
> chip uses anywhere near 128 lines so there needs to be some
> per-chip data to collect together what lines actually have
> physical pins attached and map the right names to them.
>
> The core peripherals seem to use the same lines on the
> currently known chips but the lines used for the sensor
> interface, lcd controller etc pins seem to be totally
> different between the infinity and mercury chips
>
> The code tries to collect all of the re-usable names,
> offsets etc together so that it's easy to build the extra
> per-chip data for other chips in the future.
>
> So far this only supports the MSC313 and MSC313E chips.
>
> Support for the SSC8336N (mercury5) is trivial to add once
> all of the lines have been mapped out.
>
> Signed-off-by: Daniel Palmer <daniel@...f.com>

This looks really nice, the generic hierarchical IRQchip does
its job very well here.

I saw you would send another version but this already looks
like merge material.

Certainly any remaining issues can be ironed out in-tree.

> +config GPIO_MSC313
> +       bool "MStar MSC313 GPIO support"
> +       default y if ARCH_MSTARV7
> +       depends on ARCH_MSTARV7
> +       select GPIOLIB_IRQCHIP

select IRQ_DOMAIN_HIERARCHY

since you are dependent on this.

(Else people will soon report problems with randconfig...)

> +/* The parent interrupt controller needs the GIC interrupt type set to GIC_SPI
> + * so we need to provide the fwspec. Essentially gpiochip_populate_parent_fwspec_twocell
> + * that puts GIC_SPI into the first cell.
> + */
> +static void *msc313_gpio_populate_parent_fwspec(struct gpio_chip *gc,
> +                                            unsigned int parent_hwirq,
> +                                            unsigned int parent_type)
> +{
> +       struct irq_fwspec *fwspec;
> +
> +       fwspec = kmalloc(sizeof(*fwspec), GFP_KERNEL);
> +       if (!fwspec)
> +               return NULL;
> +
> +       fwspec->fwnode = gc->irq.parent_domain->fwnode;
> +       fwspec->param_count = 3;
> +       fwspec->param[0] = GIC_SPI;
> +       fwspec->param[1] = parent_hwirq;
> +       fwspec->param[2] = parent_type;
> +
> +       return fwspec;
> +}

Clever. Looping in Marc Z so he can say if this looks allright to him.

> +static int msc313e_gpio_child_to_parent_hwirq(struct gpio_chip *chip,
> +                                            unsigned int child,
> +                                            unsigned int child_type,
> +                                            unsigned int *parent,
> +                                            unsigned int *parent_type)
> +{
> +       struct msc313_gpio *priv = gpiochip_get_data(chip);
> +       unsigned int offset = priv->gpio_data->offsets[child];
> +       int ret = -EINVAL;
> +
> +       /* only the spi0 pins have interrupts on the parent
> +        * on all of the known chips and so far they are all
> +        * mapped to the same place
> +        */
> +       if (offset >= OFF_SPI0_CZ && offset <= OFF_SPI0_DO) {
> +               *parent_type = child_type;
> +               *parent = ((offset - OFF_SPI0_CZ) >> 2) + 28;
> +               ret = 0;
> +       }
> +
> +       return ret;
> +}

Neat!

> +static int msc313_gpio_probe(struct platform_device *pdev)
> +{
> +       const struct msc313_gpio_data *match_data;
> +       struct msc313_gpio *gpio;
> +       struct gpio_chip *gpiochip;
> +       struct gpio_irq_chip *gpioirqchip;
> +       struct resource *res;
> +       struct irq_domain *parent_domain;
> +       struct device_node *parent_node;
> +       int ret;
> +
> +       match_data = of_device_get_match_data(&pdev->dev);

There is a lot of referencing &pdev->dev.

I would add a local variable like this:

struct device *dev = &pdev->dev

and replace all &pdev->dev with that. It will make the code more
compact and easier to read.

Yours,
Linus Walleij