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Date:   Tue, 12 May 2020 16:41:48 +0200
From:   Michael Walle <michael@walle.cc>
To:     Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-gpio <linux-gpio@vger.kernel.org>,
        linux-devicetree <devicetree@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-hwmon@vger.kernel.org,
        linux-pwm@vger.kernel.org,
        LINUXWATCHDOG <linux-watchdog@vger.kernel.org>,
        arm-soc <linux-arm-kernel@lists.infradead.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Jean Delvare <jdelvare@suse.com>,
        Guenter Roeck <linux@roeck-us.net>,
        Lee Jones <lee.jones@linaro.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        =?UTF-8?Q?Uwe_Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Shawn Guo <shawnguo@kernel.org>, Li Yang <leoyang.li@nxp.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <maz@kernel.org>, Mark Brown <broonie@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v3 10/16] gpio: add a reusable generic gpio_chip using
 regmap
In-Reply-To: <CAMpxmJV3XTOxuoKeV-z2d75qWqHkgvV9419tfe3idDeKwoeoLA@mail.gmail.com>
References: <20200423174543.17161-1-michael@walle.cc>
 <20200423174543.17161-11-michael@walle.cc>
 <CAMpxmJV3XTOxuoKeV-z2d75qWqHkgvV9419tfe3idDeKwoeoLA@mail.gmail.com>
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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
>>