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

Michael Walle
2020-05-12T14:42:05Z

Am 2020-05-12 14:48, schrieb Bartosz Golaszewski:
> czw., 23 kwi 2020 o 19:46 Michael Walle <michael@walle.cc> napisał(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@walle.cc>
>> ---
>
> 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@walle.cc>
>> + */
>> +
>> +#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?
sure

>> + 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@walle.cc>");
>> +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?

Then the driver has to set GPIO_REGMAP_ADDR_ZERO or use the convenience
macro GPIO_REGMAP_ADDR.

So you can have

struct gpio_regmap_config config = { 0 };
config.reg_dat_base = 0x10;
config.reg_dir_out_base = 0x20;

or

config.reg_dat_base = GPIO_REGMAP_ADDR_ZERO;

or if you can't be sure if the RHS value might be zero:

config.reg_dat_base = GPIO_REGMAP_ADDR(reg);

> Maybe drop GPIO_REGMAP_ADDR and require users to set unused registers
> to GPIO_REGMAP_ADDR_ZERO?

Thats bad because:
* you'd have to set plenty of unused base registers for a simple driver
* if there will be additional properties in the future, you have to
touch
all other drivers, because they are initialized as 0 (ie. valid reg
0).

>> +/**
>> + * 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?
good catch.

> Also: why the limitation of only supporting one at a time?

they should be exclusive, either you have a register where you set the
output bits to one, or the input bits. Maybe this need a bit more
context
above. in gpio-mmio.c you can set both and both are used in
set_direction(), but only one is read in get_direction().

That being said, I have no strong opinion wether they should be
exclusive
or not, besides the symmetry of set_/get_direction().

-michael

>
>> + * @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
>>