Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using regmap

From: Michael Walle
Date: Mon Apr 06 2020 - 06:10:43 EST

Next message: Alexander Filippov: "[PATCH] ARM: DTS: Aspeed: Add YADRO Nicole BMC"
Previous message: Johan Jonker: "Re: [PATCH] arm64: dts: rockchip: remove disable-wp from rk3308-roc-cc emmc node"
In reply to: Bartosz Golaszewski: "Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using regmap"
Next in thread: Michael Walle: "[PATCH v2 05/16] dt-bindings: mfd: Add bindings for sl28cpld"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Hi Bartosz, Hi Mark Brown,

Am 2020-04-06 09:47, schrieb Bartosz Golaszewski:

czw., 2 kwi 2020 o 22:37 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
instanciated 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>

Hi Michael,

Thanks for doing this! When looking at other generic drivers:
gpio-mmio and gpio-reg I can see there are some corner-cases and more
specific configuration options we could add

I didn't want to copy every bit without being able to test it.

but it's not a blocker,
we'll probably be extending this one as we convert more drivers to
using it.

correct, that was also my plan.

Personally I'd love to see gpio-mmio and gpio-reg removed
and replaced by a single, generic regmap interface eventually.

agreed.

---
drivers/gpio/Kconfig | 4 +
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-regmap.c | 320 ++++++++++++++++++++++++++++++++++++
include/linux/gpio-regmap.h | 88 ++++++++++
4 files changed, 413 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 1b96169d84f7..a8e148f4b2e0 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..cc4437dc0521
--- /dev/null
+++ b/drivers/gpio/gpio-regmap.c
@@ -0,0 +1,320 @@
+// 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_data {
+ struct gpio_chip gpio_chip;
+ struct gpio_regmap *gpio;
+};
+
+/**
+ * gpio_regmap_simple_xlate() - translate base/offset to reg/mask
+ *
+ * Use a simple linear mapping to translate the offset to the bitmask.
+ */
+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;
+}
+EXPORT_SYMBOL_GPL(gpio_regmap_simple_xlate);

Why does this need to be exported?

Mh, the idea was that a user could also set this xlate() by himself (for
whatever reason). But since it is the default, it is not really necessary.
That being said, I don't care if its only local to this module.

+
+static int gpio_regmap_get(struct gpio_chip *chip, unsigned int offset)
+{
+ struct gpio_regmap_data *data = gpiochip_get_data(chip);
+ struct gpio_regmap *gpio = data->gpio;
+ unsigned int base;
+ unsigned int val, reg, mask;

This can fit on a single line with base. Same elsewhere.

+ int ret;
+
+ /* we might not have an output register if we are input only */
+ if (gpio->reg_dat_base.valid)
+ base = gpio->reg_dat_base.addr;
+ else
+ base = gpio->reg_set_base.addr;
+
+ 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_data *data = gpiochip_get_data(chip);
+ struct gpio_regmap *gpio = data->gpio;
+ unsigned int base = gpio->reg_set_base.addr;
+ 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_data *data = gpiochip_get_data(chip);
+ struct gpio_regmap *gpio = data->gpio;
+ unsigned int base;
+ unsigned int reg, mask;
+
+ if (val)
+ base = gpio->reg_set_base.addr;
+ else
+ base = gpio->reg_clr_base.addr;
+
+ 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_data *data = gpiochip_get_data(chip);
+ struct gpio_regmap *gpio = data->gpio;
+ unsigned int val, reg, mask;
+ unsigned int base;
+ int invert;
+ int ret;
+
+ if (gpio->reg_dir_out_base.valid) {
+ base = gpio->reg_dir_out_base.addr;
+ invert = 0;
+ } else if (gpio->reg_dir_in_base.valid) {
+ base = gpio->reg_dir_in_base.addr;
+ 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_data *data = gpiochip_get_data(chip);
+ struct gpio_regmap *gpio = data->gpio;
+ unsigned int val, reg, mask;
+ unsigned int base;
+ int invert;
+ int ret;
+
+ if (gpio->reg_dir_out_base.valid) {
+ base = gpio->reg_dir_out_base.addr;
+ invert = 0;
+ } else if (gpio->reg_dir_in_base.valid) {
+ base = gpio->reg_dir_in_base.addr;
+ 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);
+}
+
+static int gpio_regmap_to_irq(struct gpio_chip *chip, unsigned int offset)
+{
+ struct gpio_regmap_data *data = gpiochip_get_data(chip);
+ struct gpio_regmap *gpio = data->gpio;
+
+ /* the user might have its own .to_irq callback */
+ if (gpio->to_irq)
+ return gpio->to_irq(gpio, offset);
+
+ return irq_create_mapping(gpio->irq_domain, offset);
+}
+
+/**
+ * gpio_regmap_register() - Register a generic regmap GPIO controller
+ *
+ * @gpio: gpio_regmap device to register
+ *
+ * Returns 0 on success or an errno on failure.
+ */
+int gpio_regmap_register(struct gpio_regmap *gpio)
+{
+ struct gpio_regmap_data *d;
+ struct gpio_chip *chip;
+ int ret;
+
+ if (!gpio->parent)
+ return -EINVAL;
+
+ if (!gpio->ngpio)
+ return -EINVAL;
+
+ /* we need at least one */
+ if (!gpio->reg_dat_base.valid && !gpio->reg_set_base.valid)
+ return -EINVAL;
+
+ /* we don't support having both registers simulaniously for now */
+ if (gpio->reg_dir_out_base.valid && gpio->reg_dir_in_base.valid)
+ return -EINVAL;
+
+ /* if not set, assume they are consecutive */
+ if (!gpio->reg_stride)
+ gpio->reg_stride = 1;
+
+ /* if not set, assume there is only one register */
+ if (!gpio->ngpio_per_reg)
+ gpio->ngpio_per_reg = gpio->ngpio;
+
+ if (!gpio->reg_mask_xlate)
+ gpio->reg_mask_xlate = gpio_regmap_simple_xlate;
+
+ d = kzalloc(sizeof(*d), GFP_KERNEL);
+ if (!d)
+ return -ENOMEM;
+
+ gpio->data = d;
+ d->gpio = gpio;
+
+ chip = &d->gpio_chip;
+ chip->parent = gpio->parent;
+ chip->label = gpio->label;
+ chip->base = -1;
+ chip->ngpio = gpio->ngpio;
+ chip->can_sleep = true;
+ chip->get = gpio_regmap_get;
+
+ if (!chip->label)
+ chip->label = dev_name(gpio->parent);
+
+ if (gpio->reg_set_base.valid && gpio->reg_clr_base.valid)
+ chip->set = gpio_regmap_set_with_clear;
+ else if (gpio->reg_set_base.valid)
+ chip->set = gpio_regmap_set;
+
+ if (gpio->reg_dir_in_base.valid || gpio->reg_dir_out_base.valid) {
+ chip->get_direction = gpio_regmap_get_direction;
+ chip->direction_input = gpio_regmap_direction_input;
+ chip->direction_output = gpio_regmap_direction_output;
+ }
+
+ if (gpio->irq_domain)
+ chip->to_irq = gpio_regmap_to_irq;
+
+ ret = gpiochip_add_data(chip, d);
+ if (ret < 0)
+ goto err_alloc;
+
+ return 0;
+
+err_alloc:
+ kfree(d);
+ return 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->data->gpio_chip);
+ kfree(gpio->data);
+}
+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.
+ */
+int devm_gpio_regmap_register(struct device *dev, struct gpio_regmap *gpio)
+{
+ struct gpio_regmap **ptr;
+ int ret;
+
+ ptr = devres_alloc(devm_gpio_regmap_unregister, sizeof(*ptr),
+ GFP_KERNEL);
+ if (!ptr)
+ return -ENOMEM;
+
+ ret = gpio_regmap_register(gpio);
+ if (ret) {
+ devres_free(ptr);
+ return ret;
+ }
+
+ *ptr = gpio;
+ devres_add(dev, ptr);
+
+ return 0;
+}
+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..ad63955e0e43
--- /dev/null
+++ b/include/linux/gpio-regmap.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_GPIO_REGMAP_H
+#define _LINUX_GPIO_REGMAP_H
+
+struct gpio_regmap_addr {
+ unsigned int addr;
+ bool valid;
+};

I'm not quite sure what the meaning behind the valid field here is.
When would we potentially set it to false?

Some base addresses are optional, but on the other hand, a base address
of 0 could also be valid. So I cannot use 0 as an indicator whether a
base address is set or not. The generic mmio driver has some special
case for the ack base, where there is a use_ack flag which forces to
use the ack register even if its zero. So I've had a look at the kernel
if there is a better idiom for that, but I haven't found anything.

So the best from a user perspective I've could come up with was:

->base_reg = GPIO_REGMAP_ADDR(addr);

I'm open for suggestions.

+#define GPIO_REGMAP_ADDR(_addr) \
+ ((struct gpio_regmap_addr) { .addr = _addr, .valid = true })
+
+/**
+ * struct gpio_regmap - Description of a generic regmap gpio_chip.
+ *
+ * @parent: The parent device
+ * @regmap: The regmap use to access the registers

s/use/used/

+ * 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
+ * @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.
+ * @to_irq: (Optional) Maps GPIO offset to a irq number.
+ * By default assumes a linear mapping of the
+ * given irq_domain.
+ * @driver_data: Pointer to the drivers private data. Not used by
+ * gpio-regmap.
+ *
+ * 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.
+ */
+struct gpio_regmap {

I'd prefer to follow a pattern seen in other such APIs of calling this
structure gpio_regmap_config and creating another private structure
called gpio_regmap used in callbacks that would only contain necessary
fields.

something like the following?

struct gpio_regmap *gpio_regmap_register(struct gpio_regmap_config *)

but if that structure is private, how can a callback access individual
elements? Or do you mean private in "local to the gpio drivers"?

Also I was unsure about the naming, eg. some use
stuff_register()/stuff_unregister() and some stuff_add()/stuff_remove().

+ struct device *parent;
+ struct regmap *regmap;
+ struct gpio_regmap_data *data;
+
+ const char *label;
+ int ngpio;
+
+ struct gpio_regmap_addr reg_dat_base;
+ struct gpio_regmap_addr reg_set_base;
+ struct gpio_regmap_addr reg_clr_base;
+ struct gpio_regmap_addr reg_dir_in_base;
+ struct gpio_regmap_addr 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);
+ int (*to_irq)(struct gpio_regmap *gpio, unsigned int offset);
+
+ void *driver_data;
+};
+
+static inline void gpio_regmap_set_drvdata(struct gpio_regmap *gpio,
+ void *data)
+{
+ gpio->driver_data = data;
+}
+
+static inline void *gpio_regmap_get_drvdata(struct gpio_regmap *gpio)
+{
+ return gpio->driver_data;
+}
+
+int gpio_regmap_register(struct gpio_regmap *gpio);
+void gpio_regmap_unregister(struct gpio_regmap *gpio);
+int devm_gpio_regmap_register(struct device *dev, struct gpio_regmap *gpio);
+int gpio_regmap_simple_xlate(struct gpio_regmap *gpio, unsigned int base,
+ unsigned int offset,
+ unsigned int *reg, unsigned int *mask);
+
+#endif /* _LINUX_GPIO_REGMAP_H */
--
2.20.1

Overall looks really nice. I'm happy we'll have it in v5.8.

Thanks, one thing I'm uncertain about is the regmap_irq change and if that
is acceptable. So Mark would need to comment on that.

-michael

Next message: Alexander Filippov: "[PATCH] ARM: DTS: Aspeed: Add YADRO Nicole BMC"
Previous message: Johan Jonker: "Re: [PATCH] arm64: dts: rockchip: remove disable-wp from rk3308-roc-cc emmc node"
In reply to: Bartosz Golaszewski: "Re: [PATCH v2 10/16] gpio: add a reusable generic gpio_chip using regmap"
Next in thread: Michael Walle: "[PATCH v2 05/16] dt-bindings: mfd: Add bindings for sl28cpld"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]