gpio: add a reusable generic gpio_chip using regmap

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>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200528145845.31436-3-michael@walle.cc
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 86 insertions, 0 deletions

diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
new file mode 100644
index 000000000000..4c1e6b34e824
--- /dev/null
+++ b/include/linux/gpio/regmap.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_GPIO_REGMAP_H
+#define _LINUX_GPIO_REGMAP_H
+
+struct device;
+struct gpio_regmap;
+struct irq_domain;
+struct regmap;
+
+#define GPIO_REGMAP_ADDR_ZERO ((unsigned long)(-1))
+#define GPIO_REGMAP_ADDR(addr) ((addr) ? : 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
+ * @names:		(Optional) Array of names for 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) in setting register base address
+ * @reg_dir_out_base:	(Optional) out 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.
+ *
+ * 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 register
+ * base addresses in this structure.
+ *
+ * Although all register base addresses are marked as optional, there are
+ * several rules:
+ *     1. if you only have @reg_dat_base set, then it is input-only
+ *     2. if you only have @reg_set_base set, then it is output-only
+ *     3. if you have either @reg_dir_in_base or @reg_dir_out_base set, then
+ *        you have to set both @reg_dat_base and @reg_set_base
+ *     4. if you have @reg_set_base set, you may also set @reg_clr_base to have
+ *        two different registers for setting and clearing the output. This is
+ *        also valid for the output-only case.
+ *     5. @reg_dir_in_base and @reg_dir_out_base are exclusive; is there really
+ *        hardware which has redundant registers?
+ *
+ * Note: 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;
+	const char *const *names;
+
+	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 */