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 { 72 struct device *dev = &client->dev; 73 struct gw_pld *gw; 74 int ret; 75 76 gw = devm_kzalloc(dev, sizeof(*gw), GFP_KERNEL); 77 if (!gw) 78 return -ENOMEM; 79 80 gw->chip.base = -1; 81 gw->chip.can_sleep = true; 82 gw->chip.parent = dev; 83 gw->chip.owner = THIS_MODULE; 84 gw->chip.label = dev_name(dev); 85 gw->chip.ngpio = 8; 86 gw->chip.direction_input = gw_pld_input8; 87 gw->chip.get = gw_pld_get8; 88 gw->chip.direction_output = gw_pld_output8; 89 gw->chip.set = gw_pld_set8; 90 gw->client = client; 91 92 /* 93 * The Gateworks I2C PLD chip does not properly send the acknowledge 94 * bit at all times, but we can still use the standard i2c_smbus 95 * functions by simply ignoring this bit. 96 */ 97 client->flags |= I2C_M_IGNORE_NAK; 98 gw->out = 0xFF; 99 100 i2c_set_clientdata(client, gw); 101 102 ret = devm_gpiochip_add_data(dev, &gw->chip, gw); 103 if (ret) 104 return ret; 105 106 dev_info(dev, "registered Gateworks PLD GPIO device\n"); 107 108 return 0; 109 } 110 111 static const struct i2c_device_id gw_pld_id[] = { 112 { "gw-pld", }, 113 { } 114 }; 115 MODULE_DEVICE_TABLE(i2c, gw_pld_id); 116 117 static const struct of_device_id gw_pld_dt_ids[] = { 118 { .compatible = "gateworks,pld-gpio", }, 119 { }, 120 }; 121 MODULE_DEVICE_TABLE(of, gw_pld_dt_ids); 122 123 static struct i2c_driver gw_pld_driver = { 124 .driver = { 125 .name = "gw_pld", 126 .of_match_table = gw_pld_dt_ids, 127 }, 128 .probe_new = gw_pld_probe, 129 .id_table = gw_pld_id, 130 }; 131 module_i2c_driver(gw_pld_driver); 132 133 MODULE_LICENSE("GPL"); 134 MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>"); 135