Re: [PATCH 2/3] gpio: Add GPIO support for Broadcom STB SoCs

Linus Walleij
2015-05-12T10:55:07Z

On Wed, May 6, 2015 at 10:37 AM, Gregory Fong <gregory.0xf0@gmail.com> wrote:

> This adds support for the GPIO IP "UPG GIO" used on Broadcom STB SoCs
> (BCM7XXX and some others). Uses basic_mmio_gpio to instantiate a
> gpio_chip for each bank. The driver assumes that it handles the base
> set of GPIOs on the system and that it can start its numbering sequence
> from 0, so any GPIO expanders used with it must dynamically assign GPIO
> numbers after this driver has finished registering its GPIOs.
>
> Does not implement the interrupt-controller portion yet, will be done in a
> future commit.
>
> List-usage-fixed-by: Brian Norris <computersforpeace@gmail.com>
> Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com>

(...)
> arch/arm/mach-bcm/Kconfig | 1 +
(...)
> --- a/arch/arm/mach-bcm/Kconfig
> +++ b/arch/arm/mach-bcm/Kconfig
> @@ -144,6 +144,7 @@ config ARCH_BRCMSTB
> select BRCMSTB_GISB_ARB
> select BRCMSTB_L2_IRQ
> select BCM7120_L2_IRQ
> + select ARCH_WANT_OPTIONAL_GPIOLIB

Please remove this from this patch. I don't want to patch around
in the platforms from the GPIO tree. Take this oneliner through
ARM SoC.

> +config GPIO_BRCMSTB
> + tristate "BRCMSTB GPIO support"
> + default y if ARCH_BRCMSTB
> + depends on OF_GPIO && (ARCH_BRCMSTB || COMPILE_TEST)
> + select GPIO_GENERIC

Nice.

> +++ b/drivers/gpio/gpio-brcmstb.c
(...)
> +
> +#include <linux/bitops.h>
> +#include <linux/gpio.h>

#include <linux/gpio/driver.h>

should be sufficient.

> +struct brcmstb_gpio_bank {
> + struct list_head node;
> + int id;
> + struct bgpio_chip bgc;
> + u32 imask; /* irq mask shadow register */

Why? Is it a write-only register that can't be read back?

> + struct brcmstb_gpio_priv *parent_priv; /* used in interrupt handler */

...and this patch does not enable IRQs...

> +struct brcmstb_gpio_priv {
> + struct list_head bank_list;
> + void __iomem *reg_base;
> + int num_banks;
> + struct platform_device *pdev;
> + int gpio_base;

Usually we don't like it when you hardcode gpio_base, and this
field should anyway be present inside the bgpio_chip.gc.base
isn't it?

> +#define GPIO_PER_BANK 32
> +#define GPIO_BANK(gpio) ((gpio) >> 5)
> +/* assumes GPIO_PER_BANK is a multiple of 2 */
> +#define GPIO_BIT(gpio) ((gpio) & (GPIO_PER_BANK - 1))

But this macro and GPIO_PER_BANK does not respect the DT binding
stating the number of used lines.

You need to call these MAX_GPIO_PER_BANK or something.

> +static int brcmstb_gpio_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct device_node *np = dev->of_node;
> + void __iomem *reg_base;
> + struct brcmstb_gpio_priv *priv;
> + struct resource *res;
> + struct property *prop;
> + const __be32 *p;
> + u32 bank_width;
> + int err;
> + static int gpio_base;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + reg_base = devm_ioremap_resource(dev, res);
> + if (IS_ERR(reg_base))
> + return PTR_ERR(reg_base);
> +
> + priv->gpio_base = gpio_base;
> + priv->reg_base = reg_base;
> + priv->pdev = pdev;
> +
> + INIT_LIST_HEAD(&priv->bank_list);
> + if (brcmstb_gpio_sanity_check_banks(dev, np, res))
> + return -EINVAL;
> +
> + of_property_for_each_u32(np, "brcm,gpio-bank-widths", prop, p,
> + bank_width) {
> + struct brcmstb_gpio_bank *bank;
> + struct bgpio_chip *bgc;
> + struct gpio_chip *gc;
> +
> + bank = devm_kzalloc(dev, sizeof(*bank), GFP_KERNEL);
> + if (!bank) {
> + err = -ENOMEM;
> + goto fail;
> + }
> +
> + bank->parent_priv = priv;
> + bank->id = priv->num_banks;
> +
> + /*
> + * Regs are 4 bytes wide, have data reg, no set/clear regs,
> + * and direction bits have 0 = output and 1 = input
> + */
> + bgc = &bank->bgc;
> + err = bgpio_init(bgc, dev, 4,
> + reg_base + GIO_DATA(bank->id),
> + NULL, NULL, NULL,
> + reg_base + GIO_IODIR(bank->id), 0);
> + if (err) {
> + dev_err(dev, "bgpio_init() failed\n");
> + goto fail;
> + }
> +
> + gc = &bgc->gc;
> + gc->of_node = np;
> + gc->owner = THIS_MODULE;
> + gc->label = np->full_name;
> + gc->base = gpio_base;

I strongly suggest that you try using -1 as base here instead
for dynamic assignment of GPIO numbers.

> + gc->of_gpio_n_cells = 2;
> + gc->of_xlate = brcmstb_gpio_of_xlate;
> +
> + if (bank_width <= 0 || bank_width > GPIO_PER_BANK) {
> + gc->ngpio = GPIO_PER_BANK;
> + dev_warn(dev, "Invalid bank width %d, assume %d\n",
> + bank_width, gc->ngpio);

I wonder if this should not simply return an error.
If that number is wrong the DTS is completely screwed up.

> + } else {
> + gc->ngpio = bank_width;
> + }
> +
> + bank->imask =
> + bgc->read_reg(reg_base + GIO_MASK(bank->id));

And this mask also mask the unused pins as GIO_MASK()
does not respect bank_width.

> + err = gpiochip_add(gc);
> + if (err) {
> + dev_err(dev, "Could not add gpiochip for bank %d\n",
> + bank->id);
> + goto fail;
> + }
> + gpio_base += gc->ngpio;

This complicates things. Use -1 as base for dynamic assignment
of GPIO numbers.

Yours,
Linus Walleij