Re: [PATCH 3/4] gpio: vf610: add gpiolib/IRQ chip driver for Vybird

Hi Linus,

Thanks for your review!

Am 2014-09-23 11:58, schrieb Linus Walleij:

On Sat, Sep 6, 2014 at 6:25 PM, Stefan Agner [off-list ref] wrote:

quoted

Add a gpiolib and IRQ chip driver for Vybrid ARM SoC using the
Vybrid's GPIO and PORT module. The driver is instanced once per
each GPIO/PORT module pair and handles 32 GPIO's.

Signed-off-by: Stefan Agner <stefan@agner.ch>

(...)

quoted

 obj-$(CONFIG_GPIO_UCB1400)     += gpio-ucb1400.o
+obj-$(CONFIG_GPIO_VF610)       += gpio-vf610.o

Some like to keep GPIOs tightly associated with a pin controller
in a file next to the pin controller.

I.e. in drivers/pinctrl/freescale/gpio-vf610.c

But this works too. Any preference?

The other Freescale GPIO drivers (e.g. gpio-mxs.c/gpio-mxc.c) are
located under drivers/gpio/ hence I would prefer to leave them there,
even we use pinctrl here. Unless someone at Freescale has another
opinion on this?

quoted

+#define GPIO_PER_PORT          32

Very generic define. VF610_GPIOS_PER_PORT?

Agreed

quoted

+struct vf610_gpio_port {
+       struct gpio_chip gc;
+       void __iomem *base;
+       void __iomem *gpio_base;
+       u8 irqc[GPIO_PER_PORT];
+       int irq;

irq? Why do you need to keep this around?

quoted

+static const struct of_device_id vf610_gpio_dt_ids[] = {
+       { .compatible = "fsl,vf610-gpio" },
+       { /* sentinel */ }
+};
+
+static inline void vf610_gpio_writel(u32 val, void __iomem *reg)
+{
+       __raw_writel(val, reg);

Use writel_relaxed() instead unless you can explain why you want this.

(Same for all occurences.)

Agreed, I have don't know why I used the __raw variant here. I think its
because copied this two stubs from gpio-tegra.c.

quoted

+static int vf610_gpio_get(struct gpio_chip *gc, unsigned int gpio)
+{
+       struct vf610_gpio_port *port =
+               container_of(gc, struct vf610_gpio_port, gc);
+
+       return !!(vf610_gpio_readl(port->gpio_base + GPIO_PDIR) & 1 << gpio);

#include <linux/bitops.h>

... & BIT(gpio)

quoted

+static void vf610_gpio_set(struct gpio_chip *gc, unsigned int gpio, int val)
+{
+       struct vf610_gpio_port *port =
+               container_of(gc, struct vf610_gpio_port, gc);
+       unsigned long mask = 1 << gpio;

= BIT(gpio);

quoted

+static void vf610_gpio_irq_handler(u32 irq, struct irq_desc *desc)
+{
+       struct vf610_gpio_port *port = irq_get_handler_data(irq);
+       struct irq_chip *chip = irq_desc_get_chip(desc);
+       int pin;
+       unsigned long irq_isfr;
+
+       chained_irq_enter(chip, desc);
+
+       irq_isfr = vf610_gpio_readl(port->base + PORT_ISFR);
+
+       for_each_set_bit(pin, &irq_isfr, GPIO_PER_PORT) {
+               vf610_gpio_writel(1 << pin, port->base + PORT_ISFR);

BIT(pin)

(etc)

Ok, will replace those bit operations.

quoted

+       port->irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
+       if (port->irq == NO_IRQ)
+               return -ENODEV;

Can't you just use a local int irq; variable for this?

quoted

+static int __init gpio_vf610_init(void)
+{
+       return platform_driver_register(&vf610_gpio_driver);
+}
+postcore_initcall(gpio_vf610_init);

postcore again. I don't like this, can you get rid of it?

I guess we could load this driver easily a bit later. IMHO, since lots
of other driver use GPIO's, we should it load before all the drivers
gets loaded (before device_initcall).

Most GPIO driver do this, some statistic again:
$ grep -h -o ".*_initcall" drivers/gpio/*.c | sort | uniq -c | sort -n
-r
     33 subsys_initcall
     14 postcore_initcall
      2 device_initcall
      2 arch_initcall
      1 late_initcall
      1 core_initcall

My proposal:
Use subsys_initcall (which is called after arch_initcall) in this GPIO
driver and leave the pinctrl driver as arch_initcall. This way we are
absolutely sure that the GPIO driver gets loaded after the pinctrl and
also leave the pinctrl at its current value.

--
Stefan

Overall the driver looks very nice except for these nitty gritty details.

Yours,
Linus Walleij