Re: [PATCH v3 10/16] gpio: add a reusable generic gpio_chip using regmap

From: Bartosz Golaszewski
Date: Tue May 12 2020 - 08:48:43 EST

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czw., 23 kwi 2020 o 19:46 Michael Walle <michael@xxxxxxxx> napisaÅ(a):
>
> There are quite a lot simple GPIO controller which are using regmap to
> access the hardware. This driver tries to be a base to unify existing
> code into one place. This won't cover everything but it should be a good
> starting point.
>
> It does not implement its own irq_chip because there is already a
> generic one for regmap based devices. Instead, the irq_chip will be
> instantiated in the parent driver and its irq domain will be associate
> to this driver.
>
> For now it consists of the usual registers, like set (and an optional
> clear) data register, an input register and direction registers.
> Out-of-the-box, it supports consecutive register mappings and mappings
> where the registers have gaps between them with a linear mapping between
> GPIO offset and bit position. For weirder mappings the user can register
> its own .xlate().
>
> Signed-off-by: Michael Walle <michael@xxxxxxxx>
> ---

This looks good to me. Please see some nits below.

> drivers/gpio/Kconfig | 4 +
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-regmap.c | 343 ++++++++++++++++++++++++++++++++++++
> include/linux/gpio-regmap.h | 69 ++++++++
> 4 files changed, 417 insertions(+)
> create mode 100644 drivers/gpio/gpio-regmap.c
> create mode 100644 include/linux/gpio-regmap.h
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 8ef2179fb999..ae3a49a2e970 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -73,6 +73,10 @@ config GPIO_GENERIC
> depends on HAS_IOMEM # Only for IOMEM drivers
> tristate
>
> +config GPIO_REGMAP
> + depends on REGMAP
> + tristate
> +
> # put drivers in the right section, in alphabetical order
>
> # This symbol is selected by both I2C and SPI expanders
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index b2cfc21a97f3..93e139fdfa57 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -12,6 +12,7 @@ obj-$(CONFIG_GPIO_SYSFS) += gpiolib-sysfs.o
> obj-$(CONFIG_GPIO_ACPI) += gpiolib-acpi.o
>
> # Device drivers. Generally keep list sorted alphabetically
> +obj-$(CONFIG_GPIO_REGMAP) += gpio-regmap.o
> obj-$(CONFIG_GPIO_GENERIC) += gpio-generic.o
>
> # directly supported by gpio-generic
> diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
> new file mode 100644
> index 000000000000..04939c0a22f9
> --- /dev/null
> +++ b/drivers/gpio/gpio-regmap.c
> @@ -0,0 +1,343 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * regmap based generic GPIO driver
> + *
> + * Copyright 2019 Michael Walle <michael@xxxxxxxx>
> + */
> +
> +#include <linux/gpio/driver.h>
> +#include <linux/gpio-regmap.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +
> +struct gpio_regmap {
> + struct device *parent;
> + struct regmap *regmap;
> + struct gpio_chip gpio_chip;
> +
> + int reg_stride;
> + int ngpio_per_reg;
> + unsigned int reg_dat_base;
> + unsigned int reg_set_base;
> + unsigned int reg_clr_base;
> + unsigned int reg_dir_in_base;
> + unsigned int reg_dir_out_base;
> +
> + int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
> + unsigned int offset, unsigned int *reg,
> + unsigned int *mask);
> +
> + void *driver_data;
> +};
> +
> +static unsigned int gpio_regmap_addr(unsigned int addr)
> +{
> + return (addr == GPIO_REGMAP_ADDR_ZERO) ? 0 : addr;
> +}
> +
> +/**
> + * gpio_regmap_simple_xlate() - translate base/offset to reg/mask
> + *
> + * Use a simple linear mapping to translate the offset to the bitmask.
> + */
> +static int gpio_regmap_simple_xlate(struct gpio_regmap *gpio,
> + unsigned int base, unsigned int offset,
> + unsigned int *reg, unsigned int *mask)
> +{
> + unsigned int line = offset % gpio->ngpio_per_reg;
> + unsigned int stride = offset / gpio->ngpio_per_reg;
> +
> + *reg = base + stride * gpio->reg_stride;
> + *mask = BIT(line);
> +
> + return 0;
> +}
> +
> +static int gpio_regmap_get(struct gpio_chip *chip, unsigned int offset)
> +{
> + struct gpio_regmap *gpio = gpiochip_get_data(chip);
> + unsigned int base, val, reg, mask;
> + int ret;
> +
> + /* we might not have an output register if we are input only */
> + if (gpio->reg_dat_base)
> + base = gpio_regmap_addr(gpio->reg_dat_base);
> + else
> + base = gpio_regmap_addr(gpio->reg_set_base);
> +
> + ret = gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
> + if (ret)
> + return ret;
> +
> + ret = regmap_read(gpio->regmap, reg, &val);
> + if (ret)
> + return ret;
> +
> + return (val & mask) ? 1 : 0;
> +}
> +
> +static void gpio_regmap_set(struct gpio_chip *chip, unsigned int offset,
> + int val)
> +{
> + struct gpio_regmap *gpio = gpiochip_get_data(chip);
> + unsigned int base = gpio_regmap_addr(gpio->reg_set_base);
> + unsigned int reg, mask;
> +
> + gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
> + if (val)
> + regmap_update_bits(gpio->regmap, reg, mask, mask);
> + else
> + regmap_update_bits(gpio->regmap, reg, mask, 0);
> +}
> +
> +static void gpio_regmap_set_with_clear(struct gpio_chip *chip,
> + unsigned int offset, int val)
> +{
> + struct gpio_regmap *gpio = gpiochip_get_data(chip);
> + unsigned int base, reg, mask;
> +
> + if (val)
> + base = gpio_regmap_addr(gpio->reg_set_base);
> + else
> + base = gpio_regmap_addr(gpio->reg_clr_base);
> +
> + gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
> + regmap_write(gpio->regmap, reg, mask);
> +}
> +
> +static int gpio_regmap_get_direction(struct gpio_chip *chip,
> + unsigned int offset)
> +{
> + struct gpio_regmap *gpio = gpiochip_get_data(chip);
> + unsigned int base, val, reg, mask;
> + int invert, ret;
> +
> + if (gpio->reg_dir_out_base) {
> + base = gpio_regmap_addr(gpio->reg_dir_out_base);
> + invert = 0;
> + } else if (gpio->reg_dir_in_base) {
> + base = gpio_regmap_addr(gpio->reg_dir_in_base);
> + invert = 1;
> + } else {
> + return GPIO_LINE_DIRECTION_IN;
> + }
> +
> + ret = gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
> + if (ret)
> + return ret;
> +
> + ret = regmap_read(gpio->regmap, reg, &val);
> + if (ret)
> + return ret;
> +
> + if (!!(val & mask) ^ invert)
> + return GPIO_LINE_DIRECTION_OUT;
> + else
> + return GPIO_LINE_DIRECTION_IN;
> +}
> +
> +static int gpio_regmap_set_direction(struct gpio_chip *chip,
> + unsigned int offset, bool output)
> +{
> + struct gpio_regmap *gpio = gpiochip_get_data(chip);
> + unsigned int base, val, reg, mask;
> + int invert, ret;
> +
> + if (gpio->reg_dir_out_base) {
> + base = gpio_regmap_addr(gpio->reg_dir_out_base);
> + invert = 0;
> + } else if (gpio->reg_dir_in_base) {
> + base = gpio_regmap_addr(gpio->reg_dir_in_base);
> + invert = 1;
> + } else {
> + return 0;
> + }
> +
> + ret = gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
> + if (ret)
> + return ret;
> +
> + if (!invert)
> + val = (output) ? mask : 0;
> + else
> + val = (output) ? 0 : mask;
> +
> + return regmap_update_bits(gpio->regmap, reg, mask, val);
> +}
> +
> +static int gpio_regmap_direction_input(struct gpio_chip *chip,
> + unsigned int offset)
> +{
> + return gpio_regmap_set_direction(chip, offset, false);
> +}
> +
> +static int gpio_regmap_direction_output(struct gpio_chip *chip,
> + unsigned int offset, int value)
> +{
> + gpio_regmap_set(chip, offset, value);
> +
> + return gpio_regmap_set_direction(chip, offset, true);
> +}
> +
> +void gpio_regmap_set_drvdata(struct gpio_regmap *gpio, void *data)
> +{
> + gpio->driver_data = data;
> +}
> +EXPORT_SYMBOL_GPL(gpio_regmap_set_drvdata);
> +
> +void *gpio_regmap_get_drvdata(struct gpio_regmap *gpio)
> +{
> + return gpio->driver_data;
> +}
> +EXPORT_SYMBOL_GPL(gpio_regmap_get_drvdata);
> +
> +/**
> + * gpio_regmap_register() - Register a generic regmap GPIO controller
> + *
> + * @gpio: gpio_regmap device to register
> + *
> + * Returns 0 on success or an errno on failure.
> + */
> +struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config)
> +{
> + struct gpio_regmap *gpio;
> + struct gpio_chip *chip;
> + int ret;
> +
> + if (!config->parent)
> + return ERR_PTR(-EINVAL);
> +
> + if (!config->ngpio)
> + return ERR_PTR(-EINVAL);
> +
> + /* we need at least one */
> + if (!config->reg_dat_base && !config->reg_set_base)
> + return ERR_PTR(-EINVAL);
> +
> + /* we don't support having both registers simulaniously for now */
> + if (config->reg_dir_out_base && config->reg_dir_in_base)
> + return ERR_PTR(-EINVAL);
> +
> + gpio = kzalloc(sizeof(*gpio), GFP_KERNEL);
> + if (!gpio)
> + return ERR_PTR(-ENOMEM);
> +
> + gpio->parent = config->parent;
> + gpio->regmap = config->regmap;
> + gpio->ngpio_per_reg = config->ngpio_per_reg;
> + gpio->reg_stride = config->reg_stride;
> + gpio->reg_mask_xlate = config->reg_mask_xlate;
> + gpio->reg_set_base = config->reg_set_base;
> + gpio->reg_clr_base = config->reg_clr_base;
> + gpio->reg_dir_in_base = config->reg_dir_in_base;
> + gpio->reg_dir_out_base = config->reg_dir_out_base;
> +
> + /* if not set, assume there is only one register */
> + if (!gpio->ngpio_per_reg)
> + gpio->ngpio_per_reg = config->ngpio;
> +
> + /* if not set, assume they are consecutive */
> + if (!gpio->reg_stride)
> + gpio->reg_stride = 1;
> +
> + if (!gpio->reg_mask_xlate)
> + gpio->reg_mask_xlate = gpio_regmap_simple_xlate;
> +
> + chip = &gpio->gpio_chip;
> + chip->parent = config->parent;
> + chip->base = -1;
> + chip->ngpio = config->ngpio;
> + chip->can_sleep = true;
> +
> + if (!chip->label)
> + chip->label = dev_name(config->parent);
> + else
> + chip->label = config->label;
> +
> + chip->get = gpio_regmap_get;
> + if (gpio->reg_set_base && gpio->reg_clr_base)
> + chip->set = gpio_regmap_set_with_clear;
> + else if (gpio->reg_set_base)
> + chip->set = gpio_regmap_set;
> +
> + if (gpio->reg_dir_in_base || gpio->reg_dir_out_base) {
> + chip->get_direction = gpio_regmap_get_direction;
> + chip->direction_input = gpio_regmap_direction_input;
> + chip->direction_output = gpio_regmap_direction_output;
> + }
> +
> + ret = gpiochip_add_data(chip, gpio);
> + if (ret < 0) {
> + kfree(gpio);

Maybe add a second label at the end of the function?

> + return ERR_PTR(ret);
> + }
> +
> + if (config->irq_domain) {
> + ret = gpiochip_irqchip_add_domain(chip, config->irq_domain);
> + if (ret < 0)
> + goto err;
> + }
> +
> + return gpio;
> +
> +err:
> + gpiochip_remove(chip);
> + kfree(gpio);
> + return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(gpio_regmap_register);
> +
> +/**
> + * gpio_regmap_unregister() - Unregister a generic regmap GPIO controller
> + *
> + * @gpio: gpio_regmap device to unregister
> + */
> +void gpio_regmap_unregister(struct gpio_regmap *gpio)
> +{
> + gpiochip_remove(&gpio->gpio_chip);
> + kfree(gpio);
> +}
> +EXPORT_SYMBOL_GPL(gpio_regmap_unregister);
> +
> +static void devm_gpio_regmap_unregister(struct device *dev, void *res)
> +{
> + gpio_regmap_unregister(*(struct gpio_regmap **)res);
> +}
> +
> +/**
> + * devm_gpio_regmap_register() - resource managed gpio_regmap_register()
> + *
> + * @dev: device that is registering this GPIO device
> + * @gpio: gpio_regmap device to register
> + *
> + * Managed gpio_regmap_register(). For generic regmap GPIO device registered by
> + * this function, gpio_regmap_unregister() is automatically called on driver
> + * detach. See gpio_regmap_register() for more information.
> + */
> +struct gpio_regmap *devm_gpio_regmap_register(struct device *dev,
> + const struct gpio_regmap_config *config)
> +{
> + struct gpio_regmap **ptr, *gpio;
> +
> + ptr = devres_alloc(devm_gpio_regmap_unregister, sizeof(*ptr),
> + GFP_KERNEL);
> + if (!ptr)
> + return ERR_PTR(-ENOMEM);
> +
> + gpio = gpio_regmap_register(config);
> +
> + if (!IS_ERR(gpio)) {
> + *ptr = gpio;
> + devres_add(dev, ptr);
> + } else {
> + devres_free(ptr);
> + }
> +
> + return gpio;
> +}
> +EXPORT_SYMBOL_GPL(devm_gpio_regmap_register);
> +
> +MODULE_AUTHOR("Michael Walle <michael@xxxxxxxx>");
> +MODULE_DESCRIPTION("GPIO generic regmap driver core");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/gpio-regmap.h b/include/linux/gpio-regmap.h
> new file mode 100644
> index 000000000000..a868cbcde6e9
> --- /dev/null
> +++ b/include/linux/gpio-regmap.h
> @@ -0,0 +1,69 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef _LINUX_GPIO_REGMAP_H
> +#define _LINUX_GPIO_REGMAP_H
> +
> +struct gpio_regmap;
> +
> +#define GPIO_REGMAP_ADDR_ZERO ((unsigned long)(-1))
> +#define GPIO_REGMAP_ADDR(addr) ((addr) ? : GPIO_REGMAP_ADDR_ZERO)
> +

What if the addr is actually 0? Maybe drop GPIO_REGMAP_ADDR and
require users to set unused registers to GPIO_REGMAP_ADDR_ZERO?

> +/**
> + * struct gpio_regmap_config - Description of a generic regmap gpio_chip.
> + *
> + * @parent: The parent device
> + * @regmap: The regmap used to access the registers
> + * given, the name of the device is used
> + * @label: (Optional) Descriptive name for GPIO controller.
> + * If not given, the name of the device is used.
> + * @ngpio: Number of GPIOs
> + * @reg_dat_base: (Optional) (in) register base address
> + * @reg_set_base: (Optional) set register base address
> + * @reg_clr_base: (Optional) clear register base address
> + * @reg_dir_in_base: (Optional) out setting register base address
> + * @reg_dir_out_base: (Optional) in setting register base address

The two above are inverted I think? Also: why the limitation of only
supporting one at a time?

> + * @reg_stride: (Optional) May be set if the registers (of the
> + * same type, dat, set, etc) are not consecutive.
> + * @ngpio_per_reg: Number of GPIOs per register
> + * @irq_domain: (Optional) IRQ domain if the controller is
> + * interrupt-capable
> + * @reg_mask_xlate: (Optional) Translates base address and GPIO
> + * offset to a register/bitmask pair. If not
> + * given the default gpio_regmap_simple_xlate()
> + * is used.
> + *
> + * The reg_mask_xlate translates a given base address and GPIO offset to
> + * register and mask pair. The base address is one of the given reg_*_base.
> + *
> + * All base addresses may have the special value GPIO_REGMAP_ADDR_ZERO
> + * which forces the address to the value 0.
> + */
> +struct gpio_regmap_config {
> + struct device *parent;
> + struct regmap *regmap;
> +
> + const char *label;
> + int ngpio;
> +
> + unsigned int reg_dat_base;
> + unsigned int reg_set_base;
> + unsigned int reg_clr_base;
> + unsigned int reg_dir_in_base;
> + unsigned int reg_dir_out_base;
> + int reg_stride;
> + int ngpio_per_reg;
> + struct irq_domain *irq_domain;
> +
> + int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
> + unsigned int offset, unsigned int *reg,
> + unsigned int *mask);
> +};
> +
> +struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config);
> +void gpio_regmap_unregister(struct gpio_regmap *gpio);
> +struct gpio_regmap *devm_gpio_regmap_register(struct device *dev,
> + const struct gpio_regmap_config *config);
> +void gpio_regmap_set_drvdata(struct gpio_regmap *gpio, void *data);
> +void *gpio_regmap_get_drvdata(struct gpio_regmap *gpio);
> +
> +#endif /* _LINUX_GPIO_REGMAP_H */
> --
> 2.20.1
>

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