[PATCH v3 2/2] gpio: fxl6408: add I2C GPIO expander driver

From: Francesco Dolcini
Date: Mon Mar 13 2023 - 13:11:53 EST

From: Emanuele Ghidoli <emanuele.ghidoli@xxxxxxxxxxx>

Add minimal driver for Fairchild FXL6408 8-bit I2C-controlled GPIO expander
using the generic regmap based GPIO driver (GPIO_REGMAP).

The driver implements setting the GPIO direction, reading inputs
and writing outputs.

In addition to that the FXL6408 has the following functionalities:
- allows to monitor input ports for data transitions with an interrupt pin
- all inputs can be configured with pull-up or pull-down resistors

Datasheet: https://www.onsemi.com/download/data-sheet/pdf/fxl6408-d.pdf
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@xxxxxxxxxxx>
Co-developed-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
Signed-off-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
---
v3:
* add include files: kernel.h and err.h
* refactor of fxl6408_identify and used dev_err_probe instead of dev_err
* use FXL6408_REG_INT_STS instead of FXL6408_MAX_REGISTER

v2:
* remove includes: <linux/gpio.h> and <linux/of_platform.h>
* add missing and required select REGMAP_I2C in KConfig
* use dev_err_probe()
* add "Datasheet:" tag in commit message
* improve KConfig help section
* fix newlines, multi-line comments and trailing commas
---
drivers/gpio/Kconfig | 10 +++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-fxl6408.c | 158 ++++++++++++++++++++++++++++++++++++
3 files changed, 169 insertions(+)
create mode 100644 drivers/gpio/gpio-fxl6408.c

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 13be729710f2..56a73007ebcb 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -1000,6 +1000,16 @@ config GPIO_ADNP
enough to represent all pins, but the driver will assume a
register layout for 64 pins (8 registers).

+config GPIO_FXL6408
+ tristate "FXL6408 I2C GPIO expander"
+ select GPIO_REGMAP
+ select REGMAP_I2C
+ help
+ GPIO driver for Fairchild Semiconductor FXL6408 GPIO expander.
+
+ To compile this driver as a module, choose M here: the module will
+ be called gpio-fxl6408.
+
config GPIO_GW_PLD
tristate "Gateworks PLD GPIO Expander"
depends on OF_GPIO
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index c048ba003367..12027f4c3bee 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -60,6 +60,7 @@ obj-$(CONFIG_GPIO_EP93XX) += gpio-ep93xx.o
obj-$(CONFIG_GPIO_EXAR) += gpio-exar.o
obj-$(CONFIG_GPIO_F7188X) += gpio-f7188x.o
obj-$(CONFIG_GPIO_FTGPIO010) += gpio-ftgpio010.o
+obj-$(CONFIG_GPIO_FXL6408) += gpio-fxl6408.o
obj-$(CONFIG_GPIO_GE_FPGA) += gpio-ge.o
obj-$(CONFIG_GPIO_GPIO_MM) += gpio-gpio-mm.o
obj-$(CONFIG_GPIO_GRGPIO) += gpio-grgpio.o
diff --git a/drivers/gpio/gpio-fxl6408.c b/drivers/gpio/gpio-fxl6408.c
new file mode 100644
index 000000000000..d7387c0101e2
--- /dev/null
+++ b/drivers/gpio/gpio-fxl6408.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * FXL6408 GPIO driver
+ *
+ * Copyright 2023 Toradex
+ *
+ * Author: Emanuele Ghidoli <emanuele.ghidoli@xxxxxxxxxxx>
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/regmap.h>
+#include <linux/kernel.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define FXL6408_REG_DEVICE_ID 0x01
+#define FXL6408_MF_FAIRCHILD 0b101
+#define FXL6408_MF_SHIFT 5
+
+/* Bits set here indicate that the GPIO is an output. */
+#define FXL6408_REG_IO_DIR 0x03
+
+/*
+ * Bits set here, when the corresponding bit of IO_DIR is set, drive
+ * the output high instead of low.
+ */
+#define FXL6408_REG_OUTPUT 0x05
+
+/* Bits here make the output High-Z, instead of the OUTPUT value. */
+#define FXL6408_REG_OUTPUT_HIGH_Z 0x07
+
+/* Returns the current status (1 = HIGH) of the input pins. */
+#define FXL6408_REG_INPUT_STATUS 0x0f
+
+/*
+ * Return the current interrupt status
+ * This bit is HIGH if input GPIO != default state (register 09h).
+ * The flag is cleared after being read (bit returns to 0).
+ * The input must go back to default state and change again before this flag is raised again.
+ */
+#define FXL6408_REG_INT_STS 0x13
+
+#define FXL6408_NGPIO 8
+
+static const struct regmap_range rd_range[] = {
+ { FXL6408_REG_DEVICE_ID, FXL6408_REG_DEVICE_ID },
+ { FXL6408_REG_IO_DIR, FXL6408_REG_OUTPUT },
+ { FXL6408_REG_INPUT_STATUS, FXL6408_REG_INPUT_STATUS },
+};
+
+static const struct regmap_range wr_range[] = {
+ { FXL6408_REG_DEVICE_ID, FXL6408_REG_DEVICE_ID },
+ { FXL6408_REG_IO_DIR, FXL6408_REG_OUTPUT },
+ { FXL6408_REG_OUTPUT_HIGH_Z, FXL6408_REG_OUTPUT_HIGH_Z },
+};
+
+static const struct regmap_range volatile_range[] = {
+ { FXL6408_REG_DEVICE_ID, FXL6408_REG_DEVICE_ID },
+ { FXL6408_REG_INPUT_STATUS, FXL6408_REG_INPUT_STATUS },
+};
+
+static const struct regmap_access_table rd_table = {
+ .yes_ranges = rd_range,
+ .n_yes_ranges = ARRAY_SIZE(rd_range),
+};
+
+static const struct regmap_access_table wr_table = {
+ .yes_ranges = wr_range,
+ .n_yes_ranges = ARRAY_SIZE(wr_range),
+};
+
+static const struct regmap_access_table volatile_table = {
+ .yes_ranges = volatile_range,
+ .n_yes_ranges = ARRAY_SIZE(volatile_range),
+};
+
+static const struct regmap_config regmap = {
+ .reg_bits = 8,
+ .val_bits = 8,
+
+ .max_register = FXL6408_REG_INT_STS,
+ .wr_table = &wr_table,
+ .rd_table = &rd_table,
+ .volatile_table = &volatile_table,
+
+ .cache_type = REGCACHE_RBTREE,
+ .num_reg_defaults_raw = FXL6408_REG_INT_STS + 1,
+};
+
+static int fxl6408_identify(struct device *dev, struct regmap *regmap)
+{
+ int val, ret;
+
+ ret = regmap_read(regmap, FXL6408_REG_DEVICE_ID, &val);
+ if (ret)
+ return dev_err_probe(dev, ret, "error reading DEVICE_ID\n");
+ if (val >> FXL6408_MF_SHIFT != FXL6408_MF_FAIRCHILD)
+ return dev_err_probe(dev, -ENODEV, "invalid device id 0x%02x\n", val);
+
+ return 0;
+}
+
+static int fxl6408_probe(struct i2c_client *client)
+{
+ struct device *dev = &client->dev;
+ int ret;
+ struct gpio_regmap_config gpio_config = {
+ .parent = dev,
+ .ngpio = FXL6408_NGPIO,
+ .reg_dat_base = GPIO_REGMAP_ADDR(FXL6408_REG_INPUT_STATUS),
+ .reg_set_base = GPIO_REGMAP_ADDR(FXL6408_REG_OUTPUT),
+ .reg_dir_out_base = GPIO_REGMAP_ADDR(FXL6408_REG_IO_DIR),
+ .ngpio_per_reg = FXL6408_NGPIO,
+ };
+
+ gpio_config.regmap = devm_regmap_init_i2c(client, &regmap);
+ if (IS_ERR(gpio_config.regmap))
+ return dev_err_probe(dev, PTR_ERR(gpio_config.regmap),
+ "failed to allocate register map\n");
+
+ ret = fxl6408_identify(dev, gpio_config.regmap);
+ if (ret)
+ return ret;
+
+ /* Disable High-Z of outputs, so that our OUTPUT updates actually take effect. */
+ ret = regmap_write(gpio_config.regmap, FXL6408_REG_OUTPUT_HIGH_Z, 0);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to write 'output high Z' register\n");
+
+ return PTR_ERR_OR_ZERO(devm_gpio_regmap_register(dev, &gpio_config));
+}
+
+static const __maybe_unused struct of_device_id fxl6408_dt_ids[] = {
+ { .compatible = "fcs,fxl6408" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, fxl6408_dt_ids);
+
+static const struct i2c_device_id fxl6408_id[] = {
+ { "fxl6408", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, fxl6408_id);
+
+static struct i2c_driver fxl6408_driver = {
+ .driver = {
+ .name = "fxl6408",
+ .of_match_table = fxl6408_dt_ids,
+ },
+ .probe_new = fxl6408_probe,
+ .id_table = fxl6408_id,
+};
+module_i2c_driver(fxl6408_driver);
+
+MODULE_AUTHOR("Emanuele Ghidoli <emanuele.ghidoli@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("FXL6408 GPIO driver");
+MODULE_LICENSE("GPL");
--
2.25.1