1 // SPDX-License-Identifier: GPL-2.0+ 2 // 3 // Gateworks I2C PLD GPIO expander 4 // 5 // Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org> 6 // 7 // Based on code and know-how from the OpenWrt driver: 8 // Copyright (C) 2009 Gateworks Corporation 9 // Authors: Chris Lang, Imre Kaloz 10 11 #include <linux/bits.h> 12 #include <linux/kernel.h> 13 #include <linux/slab.h> 14 #include <linux/gpio/driver.h> 15 #include <linux/i2c.h> 16 #include <linux/module.h> 17 18 /** 19 * struct gw_pld - State container for Gateworks PLD 20 * @chip: GPIO chip instance 21 * @client: I2C client 22 * @out: shadow register for the output bute 23 */ 24 struct gw_pld { 25 struct gpio_chip chip; 26 struct i2c_client *client; 27 u8 out; 28 }; 29 30 /* 31 * The Gateworks I2C PLD chip only expose one read and one write register. 32 * Writing a "one" bit (to match the reset state) lets that pin be used as an 33 * input. It is an open-drain model. 34 */ 35 static int gw_pld_input8(struct gpio_chip *gc, unsigned offset) 36 { 37 struct gw_pld *gw = gpiochip_get_data(gc); 38 39 gw->out |= BIT(offset); 40 return i2c_smbus_write_byte(gw->client, gw->out); 41 } 42 43 static int gw_pld_get8(struct gpio_chip *gc, unsigned offset) 44 { 45 struct gw_pld *gw = gpiochip_get_data(gc); 46 s32 val; 47 48 val = i2c_smbus_read_byte(gw->client); 49 50 return (val < 0) ? 0 : !!(val & BIT(offset)); 51 } 52 53 static int gw_pld_output8(struct gpio_chip *gc, unsigned offset, int value) 54 { 55 struct gw_pld *gw = gpiochip_get_data(gc); 56 57 if (value) 58 gw->out |= BIT(offset); 59 else 60 gw->out &= ~BIT(offset); 61 62 return i2c_smbus_write_byte(gw->client, gw->out); 63 } 64 65 static void gw_pld_set8(struct gpio_chip *gc, unsigned offset, int value) 66 { 67 gw_pld_output8(gc, offset, value); 68 } 69 70 static int gw_pld_probe(struct i2c_client *client, 71 const struct i2c_device_id *id) 72 { 73 struct device *dev = &client->dev; 74 struct gw_pld *gw; 75 int ret; 76 77 gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL); 78 if (!gw) 79 return -ENOMEM; 80 81 gw->chip.base = -1; 82 gw->chip.can_sleep = true; 83 gw->chip.parent = dev; 84 gw->chip.owner = THIS_MODULE; 85 gw->chip.label = dev_name(dev); 86 gw->chip.ngpio = 8; 87 gw->chip.direction_input = gw_pld_input8; 88 gw->chip.get = gw_pld_get8; 89 gw->chip.direction_output = gw_pld_output8; 90 gw->chip.set = gw_pld_set8; 91 gw->client = client; 92 93 /* 94 * The Gateworks I2C PLD chip does not properly send the acknowledge 95 * bit at all times, but we can still use the standard i2c_smbus 96 * functions by simply ignoring this bit. 97 */ 98 client->flags |= I2C_M_IGNORE_NAK; 99 gw->out = 0xFF; 100 101 i2c_set_clientdata(client, gw); 102 103 ret = devm_gpiochip_add_data(dev, &gw->chip, gw); 104 if (ret) 105 return ret; 106 107 dev_info(dev, "registered Gateworks PLD GPIO device\n"); 108 109 return 0; 110 } 111 112 static const struct i2c_device_id gw_pld_id[] = { 113 { "gw-pld", }, 114 { } 115 }; 116 MODULE_DEVICE_TABLE(i2c, gw_pld_id); 117 118 static const struct of_device_id gw_pld_dt_ids[] = { 119 { .compatible = "gateworks,pld-gpio", }, 120 { }, 121 }; 122 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids); 123 124 static struct i2c_driver gw_pld_driver = { 125 .driver = { 126 .name = "gw_pld", 127 .of_match_table = gw_pld_dt_ids, 128 }, 129 .probe = gw_pld_probe, 130 .id_table = gw_pld_id, 131 }; 132 module_i2c_driver(gw_pld_driver); 133 134 MODULE_LICENSE("GPL"); 135 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>"); 136