Haavard Skinnemoen | 1c23af9 | 2007-05-01 23:26:34 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Bitbanging I2C bus driver using the GPIO API |
| 3 | * |
| 4 | * Copyright (C) 2007 Atmel Corporation |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License version 2 as |
| 8 | * published by the Free Software Foundation. |
| 9 | */ |
| 10 | #include <linux/i2c.h> |
| 11 | #include <linux/i2c-algo-bit.h> |
| 12 | #include <linux/i2c-gpio.h> |
| 13 | #include <linux/init.h> |
| 14 | #include <linux/module.h> |
| 15 | #include <linux/platform_device.h> |
| 16 | |
| 17 | #include <asm/gpio.h> |
| 18 | |
| 19 | /* Toggle SDA by changing the direction of the pin */ |
| 20 | static void i2c_gpio_setsda_dir(void *data, int state) |
| 21 | { |
| 22 | struct i2c_gpio_platform_data *pdata = data; |
| 23 | |
| 24 | if (state) |
| 25 | gpio_direction_input(pdata->sda_pin); |
| 26 | else |
| 27 | gpio_direction_output(pdata->sda_pin, 0); |
| 28 | } |
| 29 | |
| 30 | /* |
| 31 | * Toggle SDA by changing the output value of the pin. This is only |
| 32 | * valid for pins configured as open drain (i.e. setting the value |
| 33 | * high effectively turns off the output driver.) |
| 34 | */ |
| 35 | static void i2c_gpio_setsda_val(void *data, int state) |
| 36 | { |
| 37 | struct i2c_gpio_platform_data *pdata = data; |
| 38 | |
| 39 | gpio_set_value(pdata->sda_pin, state); |
| 40 | } |
| 41 | |
| 42 | /* Toggle SCL by changing the direction of the pin. */ |
| 43 | static void i2c_gpio_setscl_dir(void *data, int state) |
| 44 | { |
| 45 | struct i2c_gpio_platform_data *pdata = data; |
| 46 | |
| 47 | if (state) |
| 48 | gpio_direction_input(pdata->scl_pin); |
| 49 | else |
| 50 | gpio_direction_output(pdata->scl_pin, 0); |
| 51 | } |
| 52 | |
| 53 | /* |
| 54 | * Toggle SCL by changing the output value of the pin. This is used |
| 55 | * for pins that are configured as open drain and for output-only |
| 56 | * pins. The latter case will break the i2c protocol, but it will |
| 57 | * often work in practice. |
| 58 | */ |
| 59 | static void i2c_gpio_setscl_val(void *data, int state) |
| 60 | { |
| 61 | struct i2c_gpio_platform_data *pdata = data; |
| 62 | |
| 63 | gpio_set_value(pdata->scl_pin, state); |
| 64 | } |
| 65 | |
| 66 | int i2c_gpio_getsda(void *data) |
| 67 | { |
| 68 | struct i2c_gpio_platform_data *pdata = data; |
| 69 | |
| 70 | return gpio_get_value(pdata->sda_pin); |
| 71 | } |
| 72 | |
| 73 | int i2c_gpio_getscl(void *data) |
| 74 | { |
| 75 | struct i2c_gpio_platform_data *pdata = data; |
| 76 | |
| 77 | return gpio_get_value(pdata->scl_pin); |
| 78 | } |
| 79 | |
| 80 | static int __init i2c_gpio_probe(struct platform_device *pdev) |
| 81 | { |
| 82 | struct i2c_gpio_platform_data *pdata; |
| 83 | struct i2c_algo_bit_data *bit_data; |
| 84 | struct i2c_adapter *adap; |
| 85 | int ret; |
| 86 | |
| 87 | pdata = pdev->dev.platform_data; |
| 88 | if (!pdata) |
| 89 | return -ENXIO; |
| 90 | |
| 91 | ret = -ENOMEM; |
| 92 | adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL); |
| 93 | if (!adap) |
| 94 | goto err_alloc_adap; |
| 95 | bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL); |
| 96 | if (!bit_data) |
| 97 | goto err_alloc_bit_data; |
| 98 | |
| 99 | ret = gpio_request(pdata->sda_pin, "sda"); |
| 100 | if (ret) |
| 101 | goto err_request_sda; |
| 102 | ret = gpio_request(pdata->scl_pin, "scl"); |
| 103 | if (ret) |
| 104 | goto err_request_scl; |
| 105 | |
| 106 | if (pdata->sda_is_open_drain) { |
| 107 | gpio_direction_output(pdata->sda_pin, 1); |
| 108 | bit_data->setsda = i2c_gpio_setsda_val; |
| 109 | } else { |
| 110 | gpio_direction_input(pdata->sda_pin); |
| 111 | bit_data->setsda = i2c_gpio_setsda_dir; |
| 112 | } |
| 113 | |
| 114 | if (pdata->scl_is_open_drain || pdata->scl_is_output_only) { |
| 115 | gpio_direction_output(pdata->scl_pin, 1); |
| 116 | bit_data->setscl = i2c_gpio_setscl_val; |
| 117 | } else { |
| 118 | gpio_direction_input(pdata->scl_pin); |
| 119 | bit_data->setscl = i2c_gpio_setscl_dir; |
| 120 | } |
| 121 | |
| 122 | if (!pdata->scl_is_output_only) |
| 123 | bit_data->getscl = i2c_gpio_getscl; |
| 124 | bit_data->getsda = i2c_gpio_getsda; |
| 125 | |
| 126 | if (pdata->udelay) |
| 127 | bit_data->udelay = pdata->udelay; |
| 128 | else if (pdata->scl_is_output_only) |
| 129 | bit_data->udelay = 50; /* 10 kHz */ |
| 130 | else |
| 131 | bit_data->udelay = 5; /* 100 kHz */ |
| 132 | |
| 133 | if (pdata->timeout) |
| 134 | bit_data->timeout = pdata->timeout; |
| 135 | else |
| 136 | bit_data->timeout = HZ / 10; /* 100 ms */ |
| 137 | |
| 138 | bit_data->data = pdata; |
| 139 | |
| 140 | adap->owner = THIS_MODULE; |
| 141 | snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id); |
| 142 | adap->algo_data = bit_data; |
| 143 | adap->dev.parent = &pdev->dev; |
| 144 | |
Atsushi Nemoto | 7e69c3a | 2007-07-12 14:12:30 +0200 | [diff] [blame^] | 145 | /* |
| 146 | * If "dev->id" is negative we consider it as zero. |
| 147 | * The reason to do so is to avoid sysfs names that only make |
| 148 | * sense when there are multiple adapters. |
| 149 | */ |
| 150 | adap->nr = pdev->id >= 0 ? pdev->id : 0; |
| 151 | ret = i2c_bit_add_numbered_bus(adap); |
Haavard Skinnemoen | 1c23af9 | 2007-05-01 23:26:34 +0200 | [diff] [blame] | 152 | if (ret) |
| 153 | goto err_add_bus; |
| 154 | |
| 155 | platform_set_drvdata(pdev, adap); |
| 156 | |
| 157 | dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n", |
| 158 | pdata->sda_pin, pdata->scl_pin, |
| 159 | pdata->scl_is_output_only |
| 160 | ? ", no clock stretching" : ""); |
| 161 | |
| 162 | return 0; |
| 163 | |
| 164 | err_add_bus: |
| 165 | gpio_free(pdata->scl_pin); |
| 166 | err_request_scl: |
| 167 | gpio_free(pdata->sda_pin); |
| 168 | err_request_sda: |
| 169 | kfree(bit_data); |
| 170 | err_alloc_bit_data: |
| 171 | kfree(adap); |
| 172 | err_alloc_adap: |
| 173 | return ret; |
| 174 | } |
| 175 | |
| 176 | static int __exit i2c_gpio_remove(struct platform_device *pdev) |
| 177 | { |
| 178 | struct i2c_gpio_platform_data *pdata; |
| 179 | struct i2c_adapter *adap; |
| 180 | |
| 181 | adap = platform_get_drvdata(pdev); |
| 182 | pdata = pdev->dev.platform_data; |
| 183 | |
| 184 | i2c_del_adapter(adap); |
| 185 | gpio_free(pdata->scl_pin); |
| 186 | gpio_free(pdata->sda_pin); |
| 187 | kfree(adap->algo_data); |
| 188 | kfree(adap); |
| 189 | |
| 190 | return 0; |
| 191 | } |
| 192 | |
| 193 | static struct platform_driver i2c_gpio_driver = { |
| 194 | .driver = { |
| 195 | .name = "i2c-gpio", |
| 196 | .owner = THIS_MODULE, |
| 197 | }, |
| 198 | .remove = __exit_p(i2c_gpio_remove), |
| 199 | }; |
| 200 | |
| 201 | static int __init i2c_gpio_init(void) |
| 202 | { |
| 203 | int ret; |
| 204 | |
| 205 | ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe); |
| 206 | if (ret) |
| 207 | printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret); |
| 208 | |
| 209 | return ret; |
| 210 | } |
| 211 | module_init(i2c_gpio_init); |
| 212 | |
| 213 | static void __exit i2c_gpio_exit(void) |
| 214 | { |
| 215 | platform_driver_unregister(&i2c_gpio_driver); |
| 216 | } |
| 217 | module_exit(i2c_gpio_exit); |
| 218 | |
| 219 | MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>"); |
| 220 | MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver"); |
| 221 | MODULE_LICENSE("GPL"); |