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Diffstat (limited to '')
| -rw-r--r-- | drivers/i2c/busses/i2c-cbus-gpio.c | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-cbus-gpio.c b/drivers/i2c/busses/i2c-cbus-gpio.c new file mode 100644 index 000000000..f8639a445 --- /dev/null +++ b/drivers/i2c/busses/i2c-cbus-gpio.c @@ -0,0 +1,284 @@ +/* + * CBUS I2C driver for Nokia Internet Tablets. + * + * Copyright (C) 2004-2010 Nokia Corporation + * + * Based on code written by Juha Yrjölä, David Weinehall, Mikko Ylinen and + * Felipe Balbi. Converted to I2C driver by Aaro Koskinen. + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file "COPYING" in the main directory of this + * archive for more details. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/io.h> +#include <linux/i2c.h> +#include <linux/slab.h> +#include <linux/delay.h> +#include <linux/errno.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/gpio/consumer.h> +#include <linux/interrupt.h> +#include <linux/platform_device.h> + +/* + * Bit counts are derived from Nokia implementation. These should be checked + * if other CBUS implementations appear. + */ +#define CBUS_ADDR_BITS 3 +#define CBUS_REG_BITS 5 + +struct cbus_host { + spinlock_t lock; /* host lock */ + struct device *dev; + struct gpio_desc *clk; + struct gpio_desc *dat; + struct gpio_desc *sel; +}; + +/** + * cbus_send_bit - sends one bit over the bus + * @host: the host we're using + * @bit: one bit of information to send + */ +static void cbus_send_bit(struct cbus_host *host, unsigned bit) +{ + gpiod_set_value(host->dat, bit ? 1 : 0); + gpiod_set_value(host->clk, 1); + gpiod_set_value(host->clk, 0); +} + +/** + * cbus_send_data - sends @len amount of data over the bus + * @host: the host we're using + * @data: the data to send + * @len: size of the transfer + */ +static void cbus_send_data(struct cbus_host *host, unsigned data, unsigned len) +{ + int i; + + for (i = len; i > 0; i--) + cbus_send_bit(host, data & (1 << (i - 1))); +} + +/** + * cbus_receive_bit - receives one bit from the bus + * @host: the host we're using + */ +static int cbus_receive_bit(struct cbus_host *host) +{ + int ret; + + gpiod_set_value(host->clk, 1); + ret = gpiod_get_value(host->dat); + gpiod_set_value(host->clk, 0); + return ret; +} + +/** + * cbus_receive_word - receives 16-bit word from the bus + * @host: the host we're using + */ +static int cbus_receive_word(struct cbus_host *host) +{ + int ret = 0; + int i; + + for (i = 16; i > 0; i--) { + int bit = cbus_receive_bit(host); + + if (bit < 0) + return bit; + + if (bit) + ret |= 1 << (i - 1); + } + return ret; +} + +/** + * cbus_transfer - transfers data over the bus + * @host: the host we're using + * @rw: read/write flag + * @dev: device address + * @reg: register address + * @data: if @rw == I2C_SBUS_WRITE data to send otherwise 0 + */ +static int cbus_transfer(struct cbus_host *host, char rw, unsigned dev, + unsigned reg, unsigned data) +{ + unsigned long flags; + int ret; + + /* We don't want interrupts disturbing our transfer */ + spin_lock_irqsave(&host->lock, flags); + + /* Reset state and start of transfer, SEL stays down during transfer */ + gpiod_set_value(host->sel, 0); + + /* Set the DAT pin to output */ + gpiod_direction_output(host->dat, 1); + + /* Send the device address */ + cbus_send_data(host, dev, CBUS_ADDR_BITS); + + /* Send the rw flag */ + cbus_send_bit(host, rw == I2C_SMBUS_READ); + + /* Send the register address */ + cbus_send_data(host, reg, CBUS_REG_BITS); + + if (rw == I2C_SMBUS_WRITE) { + cbus_send_data(host, data, 16); + ret = 0; + } else { + ret = gpiod_direction_input(host->dat); + if (ret) { + dev_dbg(host->dev, "failed setting direction\n"); + goto out; + } + gpiod_set_value(host->clk, 1); + + ret = cbus_receive_word(host); + if (ret < 0) { + dev_dbg(host->dev, "failed receiving data\n"); + goto out; + } + } + + /* Indicate end of transfer, SEL goes up until next transfer */ + gpiod_set_value(host->sel, 1); + gpiod_set_value(host->clk, 1); + gpiod_set_value(host->clk, 0); + +out: + spin_unlock_irqrestore(&host->lock, flags); + + return ret; +} + +static int cbus_i2c_smbus_xfer(struct i2c_adapter *adapter, + u16 addr, + unsigned short flags, + char read_write, + u8 command, + int size, + union i2c_smbus_data *data) +{ + struct cbus_host *chost = i2c_get_adapdata(adapter); + int ret; + + if (size != I2C_SMBUS_WORD_DATA) + return -EINVAL; + + ret = cbus_transfer(chost, read_write == I2C_SMBUS_READ, addr, + command, data->word); + if (ret < 0) + return ret; + + if (read_write == I2C_SMBUS_READ) + data->word = ret; + + return 0; +} + +static u32 cbus_i2c_func(struct i2c_adapter *adapter) +{ + return I2C_FUNC_SMBUS_READ_WORD_DATA | I2C_FUNC_SMBUS_WRITE_WORD_DATA; +} + +static const struct i2c_algorithm cbus_i2c_algo = { + .smbus_xfer = cbus_i2c_smbus_xfer, + .smbus_xfer_atomic = cbus_i2c_smbus_xfer, + .functionality = cbus_i2c_func, +}; + +static int cbus_i2c_remove(struct platform_device *pdev) +{ + struct i2c_adapter *adapter = platform_get_drvdata(pdev); + + i2c_del_adapter(adapter); + + return 0; +} + +static int cbus_i2c_probe(struct platform_device *pdev) +{ + struct i2c_adapter *adapter; + struct cbus_host *chost; + + adapter = devm_kzalloc(&pdev->dev, sizeof(struct i2c_adapter), + GFP_KERNEL); + if (!adapter) + return -ENOMEM; + + chost = devm_kzalloc(&pdev->dev, sizeof(*chost), GFP_KERNEL); + if (!chost) + return -ENOMEM; + + if (gpiod_count(&pdev->dev, NULL) != 3) + return -ENODEV; + chost->clk = devm_gpiod_get_index(&pdev->dev, NULL, 0, GPIOD_OUT_LOW); + if (IS_ERR(chost->clk)) + return PTR_ERR(chost->clk); + chost->dat = devm_gpiod_get_index(&pdev->dev, NULL, 1, GPIOD_IN); + if (IS_ERR(chost->dat)) + return PTR_ERR(chost->dat); + chost->sel = devm_gpiod_get_index(&pdev->dev, NULL, 2, GPIOD_OUT_HIGH); + if (IS_ERR(chost->sel)) + return PTR_ERR(chost->sel); + gpiod_set_consumer_name(chost->clk, "CBUS clk"); + gpiod_set_consumer_name(chost->dat, "CBUS dat"); + gpiod_set_consumer_name(chost->sel, "CBUS sel"); + + adapter->owner = THIS_MODULE; + adapter->class = I2C_CLASS_HWMON; + adapter->dev.parent = &pdev->dev; + adapter->dev.of_node = pdev->dev.of_node; + adapter->nr = pdev->id; + adapter->timeout = HZ; + adapter->algo = &cbus_i2c_algo; + strlcpy(adapter->name, "CBUS I2C adapter", sizeof(adapter->name)); + + spin_lock_init(&chost->lock); + chost->dev = &pdev->dev; + + i2c_set_adapdata(adapter, chost); + platform_set_drvdata(pdev, adapter); + + return i2c_add_numbered_adapter(adapter); +} + +#if defined(CONFIG_OF) +static const struct of_device_id i2c_cbus_dt_ids[] = { + { .compatible = "i2c-cbus-gpio", }, + { } +}; +MODULE_DEVICE_TABLE(of, i2c_cbus_dt_ids); +#endif + +static struct platform_driver cbus_i2c_driver = { + .probe = cbus_i2c_probe, + .remove = cbus_i2c_remove, + .driver = { + .name = "i2c-cbus-gpio", + .of_match_table = of_match_ptr(i2c_cbus_dt_ids), + }, +}; +module_platform_driver(cbus_i2c_driver); + +MODULE_ALIAS("platform:i2c-cbus-gpio"); +MODULE_DESCRIPTION("CBUS I2C driver"); +MODULE_AUTHOR("Juha Yrjölä"); +MODULE_AUTHOR("David Weinehall"); +MODULE_AUTHOR("Mikko Ylinen"); +MODULE_AUTHOR("Felipe Balbi"); +MODULE_AUTHOR("Aaro Koskinen <aaro.koskinen@iki.fi>"); +MODULE_LICENSE("GPL"); |