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1/*2 * CBUS I2C driver for Nokia Internet Tablets.3 *4 * Copyright (C) 2004-2010 Nokia Corporation5 *6 * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and7 * Felipe Balbi. Converted to I2C driver by Aaro Koskinen.8 *9 * This file is subject to the terms and conditions of the GNU General10 * Public License. See the file "COPYING" in the main directory of this11 * archive for more details.12 *13 * This program is distributed in the hope that it will be useful,14 * but WITHOUT ANY WARRANTY; without even the implied warranty of15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the16 * GNU General Public License for more details.17 */18 19#include <linux/io.h>20#include <linux/i2c.h>21#include <linux/slab.h>22#include <linux/delay.h>23#include <linux/errno.h>24#include <linux/kernel.h>25#include <linux/module.h>26#include <linux/gpio/consumer.h>27#include <linux/interrupt.h>28#include <linux/platform_device.h>29 30/*31 * Bit counts are derived from Nokia implementation. These should be checked32 * if other CBUS implementations appear.33 */34#define CBUS_ADDR_BITS 335#define CBUS_REG_BITS 536 37struct cbus_host {38 spinlock_t lock; /* host lock */39 struct device *dev;40 struct gpio_desc *clk;41 struct gpio_desc *dat;42 struct gpio_desc *sel;43};44 45/**46 * cbus_send_bit - sends one bit over the bus47 * @host: the host we're using48 * @bit: one bit of information to send49 */50static void cbus_send_bit(struct cbus_host *host, unsigned bit)51{52 gpiod_set_value(host->dat, bit ? 1 : 0);53 gpiod_set_value(host->clk, 1);54 gpiod_set_value(host->clk, 0);55}56 57/**58 * cbus_send_data - sends @len amount of data over the bus59 * @host: the host we're using60 * @data: the data to send61 * @len: size of the transfer62 */63static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len)64{65 int i;66 67 for (i = len; i > 0; i--)68 cbus_send_bit(host, data & (1 << (i - 1)));69}70 71/**72 * cbus_receive_bit - receives one bit from the bus73 * @host: the host we're using74 */75static int cbus_receive_bit(struct cbus_host *host)76{77 int ret;78 79 gpiod_set_value(host->clk, 1);80 ret = gpiod_get_value(host->dat);81 gpiod_set_value(host->clk, 0);82 return ret;83}84 85/**86 * cbus_receive_word - receives 16-bit word from the bus87 * @host: the host we're using88 */89static int cbus_receive_word(struct cbus_host *host)90{91 int ret = 0;92 int i;93 94 for (i = 16; i > 0; i--) {95 int bit = cbus_receive_bit(host);96 97 if (bit < 0)98 return bit;99 100 if (bit)101 ret |= 1 << (i - 1);102 }103 return ret;104}105 106/**107 * cbus_transfer - transfers data over the bus108 * @host: the host we're using109 * @rw: read/write flag110 * @dev: device address111 * @reg: register address112 * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0113 */114static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev,115 unsigned reg, unsigned data)116{117 unsigned long flags;118 int ret;119 120 /* We don't want interrupts disturbing our transfer */121 spin_lock_irqsave(&host->lock, flags);122 123 /* Reset state and start of transfer, SEL stays down during transfer */124 gpiod_set_value(host->sel, 0);125 126 /* Set the DAT pin to output */127 gpiod_direction_output(host->dat, 1);128 129 /* Send the device address */130 cbus_send_data(host, dev, CBUS_ADDR_BITS);131 132 /* Send the rw flag */133 cbus_send_bit(host, rw == I2C_SMBUS_READ);134 135 /* Send the register address */136 cbus_send_data(host, reg, CBUS_REG_BITS);137 138 if (rw == I2C_SMBUS_WRITE) {139 cbus_send_data(host, data, 16);140 ret = 0;141 } else {142 ret = gpiod_direction_input(host->dat);143 if (ret) {144 dev_dbg(host->dev, "failed setting direction\n");145 goto out;146 }147 gpiod_set_value(host->clk, 1);148 149 ret = cbus_receive_word(host);150 if (ret < 0) {151 dev_dbg(host->dev, "failed receiving data\n");152 goto out;153 }154 }155 156 /* Indicate end of transfer, SEL goes up until next transfer */157 gpiod_set_value(host->sel, 1);158 gpiod_set_value(host->clk, 1);159 gpiod_set_value(host->clk, 0);160 161out:162 spin_unlock_irqrestore(&host->lock, flags);163 164 return ret;165}166 167static int cbus_i2c_smbus_xfer(struct i2c_adapter *adapter,168 u16 addr,169 unsigned short flags,170 char read_write,171 u8 command,172 int size,173 union i2c_smbus_data *data)174{175 struct cbus_host *chost = i2c_get_adapdata(adapter);176 int ret;177 178 if (size != I2C_SMBUS_WORD_DATA)179 return -EINVAL;180 181 ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr,182 command, data->word);183 if (ret < 0)184 return ret;185 186 if (read_write == I2C_SMBUS_READ)187 data->word = ret;188 189 return 0;190}191 192static u32 cbus_i2c_func(struct i2c_adapter *adapter)193{194 return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA;195}196 197static const struct i2c_algorithm cbus_i2c_algo = {198 .smbus_xfer = cbus_i2c_smbus_xfer,199 .smbus_xfer_atomic = cbus_i2c_smbus_xfer,200 .functionality = cbus_i2c_func,201};202 203static void cbus_i2c_remove(struct platform_device *pdev)204{205 struct i2c_adapter *adapter = platform_get_drvdata(pdev);206 207 i2c_del_adapter(adapter);208}209 210static int cbus_i2c_probe(struct platform_device *pdev)211{212 struct i2c_adapter *adapter;213 struct cbus_host *chost;214 215 adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter),216 GFP_KERNEL);217 if (!adapter)218 return -ENOMEM;219 220 chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL);221 if (!chost)222 return -ENOMEM;223 224 if (gpiod_count(&pdev->dev, NULL) != 3)225 return -ENODEV;226 chost->clk = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_LOW);227 if (IS_ERR(chost->clk))228 return PTR_ERR(chost->clk);229 chost->dat = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_IN);230 if (IS_ERR(chost->dat))231 return PTR_ERR(chost->dat);232 chost->sel = devm_gpiod_get_index(&pdev->dev, NULL, 2, GPIOD_OUT_HIGH);233 if (IS_ERR(chost->sel))234 return PTR_ERR(chost->sel);235 gpiod_set_consumer_name(chost->clk, "CBUS clk");236 gpiod_set_consumer_name(chost->dat, "CBUS dat");237 gpiod_set_consumer_name(chost->sel, "CBUS sel");238 239 adapter->owner = THIS_MODULE;240 adapter->class = I2C_CLASS_HWMON;241 adapter->dev.parent = &pdev->dev;242 adapter->dev.of_node = pdev->dev.of_node;243 adapter->nr = pdev->id;244 adapter->timeout = HZ;245 adapter->algo = &cbus_i2c_algo;246 strscpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name));247 248 spin_lock_init(&chost->lock);249 chost->dev = &pdev->dev;250 251 i2c_set_adapdata(adapter, chost);252 platform_set_drvdata(pdev, adapter);253 254 return i2c_add_numbered_adapter(adapter);255}256 257#if defined(CONFIG_OF)258static const struct of_device_id i2c_cbus_dt_ids[] = {259 { .compatible = "i2c-cbus-gpio", },260 { }261};262MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids);263#endif264 265static struct platform_driver cbus_i2c_driver = {266 .probe = cbus_i2c_probe,267 .remove_new = cbus_i2c_remove,268 .driver = {269 .name = "i2c-cbus-gpio",270 .of_match_table = of_match_ptr(i2c_cbus_dt_ids),271 },272};273module_platform_driver(cbus_i2c_driver);274 275MODULE_ALIAS("platform:i2c-cbus-gpio");276MODULE_DESCRIPTION("CBUS I2C driver");277MODULE_AUTHOR("Juha Yrjölä");278MODULE_AUTHOR("David Weinehall");279MODULE_AUTHOR("Mikko Ylinen");280MODULE_AUTHOR("Felipe Balbi");281MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>");282MODULE_LICENSE("GPL");283