/*
* 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 void cbus_i2c_remove(struct platform_device *pdev)
{
struct i2c_adapter *adapter = platform_get_drvdata(pdev);
i2c_del_adapter(adapter);
}
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;
strscpy(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_new = 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 <[email protected]>");
MODULE_LICENSE("GPL");
Codebase Browser
linux