drivers/gpio/gpio-gw-pld.c

0001 // SPDX-License-Identifier: GPL-2.0+
0002 //
0003 // Gateworks I2C PLD GPIO expander
0004 //
0005 // Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
0006 //
0007 // Based on code and know-how from the OpenWrt driver:
0008 // Copyright (C) 2009 Gateworks Corporation
0009 // Authors: Chris Lang, Imre Kaloz
0010
0011 #include <linux/bits.h>
0012 #include <linux/kernel.h>
0013 #include <linux/slab.h>
0014 #include <linux/gpio/driver.h>
0015 #include <linux/i2c.h>
0016 #include <linux/module.h>
0017
0018 /**
0019  * struct gw_pld - State container for Gateworks PLD
0020  * @chip: GPIO chip instance
0021  * @client: I2C client
0022  * @out: shadow register for the output bute
0023  */
0024 struct gw_pld {
0025     struct gpio_chip chip;
0026     struct i2c_client *client;
0027     u8 out;
0028 };
0029
0030 /*
0031  * The Gateworks I2C PLD chip only expose one read and one write register.
0032  * Writing a "one" bit (to match the reset state) lets that pin be used as an
0033  * input. It is an open-drain model.
0034  */
0035 static int gw_pld_input8(struct gpio_chip *gc, unsigned offset)
0036 {
0037     struct gw_pld *gw = gpiochip_get_data(gc);
0038
0039     gw->out |= BIT(offset);
0040     return i2c_smbus_write_byte(gw->client, gw->out);
0041 }
0042
0043 static int gw_pld_get8(struct gpio_chip *gc, unsigned offset)
0044 {
0045     struct gw_pld *gw = gpiochip_get_data(gc);
0046     s32 val;
0047
0048     val = i2c_smbus_read_byte(gw->client);
0049
0050     return (val < 0) ? 0 : !!(val & BIT(offset));
0051 }
0052
0053 static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value)
0054 {
0055     struct gw_pld *gw = gpiochip_get_data(gc);
0056
0057     if (value)
0058         gw->out |= BIT(offset);
0059     else
0060         gw->out &= ~BIT(offset);
0061
0062     return i2c_smbus_write_byte(gw->client, gw->out);
0063 }
0064
0065 static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value)
0066 {
0067     gw_pld_output8(gc, offset, value);
0068 }
0069
0070 static int gw_pld_probe(struct i2c_client *client,
0071             const struct i2c_device_id *id)
0072 {
0073     struct device *dev = &client->dev;
0074     struct gw_pld *gw;
0075     int ret;
0076
0077     gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL);
0078     if (!gw)
0079         return -ENOMEM;
0080
0081     gw->chip.base = -1;
0082     gw->chip.can_sleep = true;
0083     gw->chip.parent = dev;
0084     gw->chip.owner = THIS_MODULE;
0085     gw->chip.label = dev_name(dev);
0086     gw->chip.ngpio = 8;
0087     gw->chip.direction_input = gw_pld_input8;
0088     gw->chip.get = gw_pld_get8;
0089     gw->chip.direction_output = gw_pld_output8;
0090     gw->chip.set = gw_pld_set8;
0091     gw->client = client;
0092
0093     /*
0094      * The Gateworks I2C PLD chip does not properly send the acknowledge
0095      * bit at all times, but we can still use the standard i2c_smbus
0096      * functions by simply ignoring this bit.
0097      */
0098     client->flags |= I2C_M_IGNORE_NAK;
0099     gw->out = 0xFF;
0100
0101     i2c_set_clientdata(client, gw);
0102
0103     ret = devm_gpiochip_add_data(dev, &gw->chip, gw);
0104     if (ret)
0105         return ret;
0106
0107     dev_info(dev, "registered Gateworks PLD GPIO device\n");
0108
0109     return 0;
0110 }
0111
0112 static const struct i2c_device_id gw_pld_id[] = {
0113     { "gw-pld", },
0114     { }
0115 };
0116 MODULE_DEVICE_TABLE(i2c, gw_pld_id);
0117
0118 static const struct of_device_id gw_pld_dt_ids[] = {
0119     { .compatible = "gateworks,pld-gpio", },
0120     { },
0121 };
0122 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids);
0123
0124 static struct i2c_driver gw_pld_driver = {
0125     .driver = {
0126         .name = "gw_pld",
0127         .of_match_table = gw_pld_dt_ids,
0128     },
0129     .probe = gw_pld_probe,
0130     .id_table = gw_pld_id,
0131 };
0132 module_i2c_driver(gw_pld_driver);
0133
0134 MODULE_LICENSE("GPL");
0135 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");