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 device_node *np = dev->of_node; 75 struct gw_pld *gw; 76 int ret; 77 78 gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL); 79 if (!gw) 80 return -ENOMEM; 81 82 gw->chip.base = -1; 83 gw->chip.can_sleep = true; 84 gw->chip.parent = dev; 85 gw->chip.of_node = np; 86 gw->chip.owner = THIS_MODULE; 87 gw->chip.label = dev_name(dev); 88 gw->chip.ngpio = 8; 89 gw->chip.direction_input = gw_pld_input8; 90 gw->chip.get = gw_pld_get8; 91 gw->chip.direction_output = gw_pld_output8; 92 gw->chip.set = gw_pld_set8; 93 gw->client = client; 94 95 /* 96 * The Gateworks I2C PLD chip does not properly send the acknowledge 97 * bit at all times, but we can still use the standard i2c_smbus 98 * functions by simply ignoring this bit. 99 */ 100 client->flags |= I2C_M_IGNORE_NAK; 101 gw->out = 0xFF; 102 103 i2c_set_clientdata(client, gw); 104 105 ret = devm_gpiochip_add_data(dev, &gw->chip, gw); 106 if (ret) 107 return ret; 108 109 dev_info(dev, "registered Gateworks PLD GPIO device\n"); 110 111 return 0; 112 } 113 114 static const struct i2c_device_id gw_pld_id[] = { 115 { "gw-pld", }, 116 { } 117 }; 118 MODULE_DEVICE_TABLE(i2c, gw_pld_id); 119 120 static const struct of_device_id gw_pld_dt_ids[] = { 121 { .compatible = "gateworks,pld-gpio", }, 122 { }, 123 }; 124 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids); 125 126 static struct i2c_driver gw_pld_driver = { 127 .driver = { 128 .name = "gw_pld", 129 .of_match_table = gw_pld_dt_ids, 130 }, 131 .probe = gw_pld_probe, 132 .id_table = gw_pld_id, 133 }; 134 module_i2c_driver(gw_pld_driver); 135 136 MODULE_LICENSE("GPL"); 137 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>"); 138