diff options
Diffstat (limited to 'drivers/gpio/gpio-i2c.c')
| -rw-r--r-- | drivers/gpio/gpio-i2c.c | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/drivers/gpio/gpio-i2c.c b/drivers/gpio/gpio-i2c.c new file mode 100644 index 000000000000..f24b7df4c69d --- /dev/null +++ b/drivers/gpio/gpio-i2c.c @@ -0,0 +1,206 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * simple parameterized no-irq of_driven i2c->gpio expander, + * cut down from gpio-pcf857x.c to be totally device-tree driven. + * + * Suitable for any "memory-like" device, where a 1-byte i2c read yields data + * which can safely be written back, possibly with a bit changed, with the + * effect of changing only the output level of that bit's GPIO pin. + * + * Copyright (C) 2016 Cavium Inc. + * Copyright (C) 2019 Marvell International Ltd. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/gpio.h> +#include <linux/i2c.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/slab.h> +#include <linux/spinlock.h> + +struct gpio_i2c_platform_data { + unsigned int i2c_addr; + unsigned int pins; +}; + + +static const struct of_device_id gpio_i2c_of_table[] = { + { .compatible = "gpio-i2c" }, + { } +}; +MODULE_DEVICE_TABLE(of, gpio_i2c_of_table); + +struct gpio_i2c { + unsigned int i2c_addr; + struct gpio_chip chip; + struct i2c_client *client; + struct mutex lock; /* protect 'out' */ + u8 out[]; /* software latch */ +}; + +/*-------------------------------------------------------------------------*/ + +static int gpio_i2c_get(struct gpio_chip *chip, unsigned int offset) +{ + struct gpio_i2c *gpio = container_of(chip, struct gpio_i2c, chip); + int value; + unsigned int byte = (offset >> 3); + unsigned int bit = (offset & 7); + + mutex_lock(&gpio->lock); + value = i2c_smbus_read_byte_data(gpio->client, byte); + mutex_unlock(&gpio->lock); + return (value < 0) ? 0 : ((value >> bit) & 1); +} + +static int gpio_i2c_output(struct gpio_chip *chip, + unsigned int offset, int value) +{ + struct gpio_i2c *gpio = container_of(chip, struct gpio_i2c, chip); + unsigned int byte = (offset >> 3); + unsigned int bit = (offset & 7); + unsigned int mask = (1 << bit); + int status; + u8 was; + + mutex_lock(&gpio->lock); + was = i2c_smbus_read_byte_data(gpio->client, byte); + if (value) + was |= mask; + else + was &= ~mask; + status = i2c_smbus_write_byte_data(gpio->client, byte, was); + gpio->out[byte] = was; + mutex_unlock(&gpio->lock); + + return status; +} + +static void gpio_i2c_set(struct gpio_chip *chip, unsigned int offset, int value) +{ + gpio_i2c_output(chip, offset, value); +} + +/* for open-drain: set as input by letting output go high */ +static int gpio_i2c_input(struct gpio_chip *chip, unsigned int offset) +{ + return gpio_i2c_output(chip, offset, 1); +} + +/*-------------------------------------------------------------------------*/ + +static int gpio_i2c_probe(struct i2c_client *client, + const struct i2c_device_id *id) +{ + struct gpio_i2c_platform_data *pdata = dev_get_platdata(&client->dev); + struct device_node *np = client->dev.of_node; + struct gpio_i2c *gpio; + u32 pins; + u32 i2c_addr; + int status; + + if (np) { + status = of_property_read_u32(np, "reg", &i2c_addr); + if (status < 0) { + dev_dbg(&client->dev, "missing reg property\n"); + return status; + } + status = of_property_read_u32(np, "ngpios", &pins); + if (status < 0) { + dev_dbg(&client->dev, "missing ngpios property\n"); + return status; + } + } else if (pdata) { + i2c_addr = pdata->i2c_addr; + pins = pdata->pins; + } else { + dev_dbg(&client->dev, "no platform data\n"); + return -EPROBE_DEFER; + } + + /* Allocate, initialize, and register this gpio_chip. */ + gpio = devm_kzalloc(&client->dev, + sizeof(*gpio) + (pins + 7) / 8, GFP_KERNEL); + if (!gpio) + return -ENOMEM; + + mutex_init(&gpio->lock); + + gpio->i2c_addr = i2c_addr; + gpio->chip.base = -1; + gpio->chip.can_sleep = true; + gpio->chip.parent = &client->dev; + gpio->chip.owner = THIS_MODULE; + gpio->chip.get = gpio_i2c_get; + gpio->chip.set = gpio_i2c_set; + gpio->chip.direction_input = gpio_i2c_input; + gpio->chip.direction_output = gpio_i2c_output; + gpio->chip.ngpio = pins; + gpio->chip.label = client->name; + gpio->client = client; + gpio->client->addr = i2c_addr; + i2c_set_clientdata(client, gpio); + + status = gpiochip_add(&gpio->chip); + if (status < 0) + goto fail; + + dev_info(&client->dev, "probed\n"); + + return 0; + +fail: + dev_dbg(&client->dev, "probe error %d for '%s'\n", status, + client->name); + + return status; +} + +static int gpio_i2c_remove(struct i2c_client *client) +{ + struct gpio_i2c *gpio = i2c_get_clientdata(client); + int status = 0; + + gpiochip_remove(&gpio->chip); + return status; +} + +/* this must _exist_ for i2c_device_probe() to call our probe, may be empty */ +static struct i2c_device_id empty_id_table[] = { + { }, +}; +MODULE_DEVICE_TABLE(i2c, empty_id_table); + +static struct i2c_driver gpio_i2c_driver = { + .driver = { + .name = "gpio-i2c", + .of_match_table = of_match_ptr(gpio_i2c_of_table), + }, + .probe = gpio_i2c_probe, + .remove = gpio_i2c_remove, + .id_table = empty_id_table, +}; + +module_i2c_driver(gpio_i2c_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("David Brownell"); +MODULE_AUTHOR("Peter Swain <pswain@cavium.com>"); +/* + * arguably this name defies convention, but correct(?) alias has been + * taken by the inverse function in + * drivers/i2c/busses/i2c-gpio.c:MODULE_ALIAS("platform:i2c-gpio"); + */ +MODULE_ALIAS("platform:gpio-i2c"); |