/**
* drivers/gpio/max7301.c
*
* Copyright (C) 2006 Juergen Beisert, Pengutronix
* Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* The Maxim's MAX7301 device is an SPI driven GPIO expander. There are
* 28 GPIOs. 8 of them can trigger an interrupt. See datasheet for more
* details
* Note:
* - DIN must be stable at the rising edge of clock.
* - when writing:
* - always clock in 16 clocks at once
* - at DIN: D15 first, D0 last
* - D0..D7 = databyte, D8..D14 = commandbyte
* - D15 = low -> write command
* - when reading
* - always clock in 16 clocks at once
* - at DIN: D15 first, D0 last
* - D0..D7 = dummy, D8..D14 = register address
* - D15 = high -> read command
* - raise CS and assert it again
* - always clock in 16 clocks at once
* - at DOUT: D15 first, D0 last
* - D0..D7 contains the data from the first cycle
*
* The driver exports a standard gpiochip interface
*/
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/spi/spi.h>
#include <linux/spi/max7301.h>
#include <linux/gpio.h>
#define DRIVER_NAME "max7301"
/*
* Pin configurations, see MAX7301 datasheet page 6
*/
#define PIN_CONFIG_MASK 0x03
#define PIN_CONFIG_IN_PULLUP 0x03
#define PIN_CONFIG_IN_WO_PULLUP 0x02
#define PIN_CONFIG_OUT 0x01
#define PIN_NUMBER 28
/*
* Some registers must be read back to modify.
* To save time we cache them here in memory
*/
struct max7301 {
struct mutex lock;
u8 port_config[8]; /* field 0 is unused */
u32 out_level; /* cached output levels */
struct gpio_chip chip;
struct spi_device *spi;
};
/**
* max7301_write - Write a new register content
* @spi: The SPI device
* @reg: Register offset
* @val: Value to write
*
* A write to the MAX7301 means one message with one transfer
*
* Returns 0 if successful or a negative value on error
*/
static int max7301_write(struct spi_device *spi, unsigned int reg, unsigned int val)
{
u16 word = ((reg & 0x7F) << 8) | (val & 0xFF);
return spi_write(spi, (const u8 *)&word, sizeof(word));
}
/**
* max7301_read - Read back register content
* @spi: The SPI device
* @reg: Register offset
*
* A read from the MAX7301 means two transfers; here, one message each
*
* Returns positive 8 bit value from device if successful or a
* negative value on error
*/
static int max7301_read(struct spi_device *spi, unsigned int reg)
{
int ret;
u16 word;
word = 0x8000 | (reg << 8);
ret = spi_write(spi, (const u8 *)&word, sizeof(word));
if (ret)
return ret;
/*
* This relies on the fact, that a transfer with NULL tx_buf shifts out
* zero bytes (=NOOP for MAX7301)
*/
ret = spi_read(spi, (u8 *)&word, sizeof(word));
if (ret)
return ret;
return word & 0xff;
}
static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
{
struct max7301 *ts = container_of(chip, struct max7301, chip);
u8 *config;
int ret;
/* First 4 pins are unused in the controller */
offset += 4;
config = &ts->port_config[offset >> 2];
mutex_lock(&ts->lock);
/* Standard GPIO API doesn't support pull-ups, has to be extended.
* Hard-coding no pollup for now. */
*config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
mutex_unlock(&ts->lock);
return ret;
}
static int __max7301_set(struct max7301 *ts, unsigned offset, int value)
{
if (value) {
ts->out_level |= 1 << offset;
return max7301_write(ts->spi, 0x20 + offset, 0x01);
} else {
ts->out_level &= ~(1 << offset);
return max7301_write(ts->spi, 0x20 + offset, 0x00);
}
}
static int max7301_direction_output(struct gpio_chip *chip, unsigned offset,
int value)
{
struct max7301 *ts = container_of(chip, struct max7301, chip);
u8 *config;
int ret;
/* First 4 pins are unused in the controller */
offset += 4;
config = &ts->port_config[offset >> 2];
mutex_lock(&ts->lock);
*config = (*config & ~(3 << (offset & 3))) | (1 << (offset & 3));
ret = __max7301_set(ts, offset, value);
if (!ret)
ret = max7301_write(ts->spi, 0x08 + (offset >> 2), *config);
mutex_unlock(&ts->lock);
return ret;
}
static int max7301_get(struct gpio_chip *chip, unsigned offset)
{
struct max7301 *ts = container_of(chip, struct max7301, chip);
int config, level = -EINVAL;
/* First 4 pins are unused in the controller */
offset += 4;
mutex_lock(&ts->lock);
config = (ts->port_config[offset >> 2] >> ((offset & 3) * 2)) & 3;
switch (config) {
case 1:
/* Output: return cached level */
level = !!(ts->out_level & (1 << offset));
break;
case 2:
case 3:
/* Input: read out */
level = max7301_read(ts->spi, 0x20 + offset) & 0x01;
}
mutex_unlock(&ts->lock);
return level;
}
static void max7301_set(struct gpio_chip *chip, unsigned offset, int value)
{
struct max7301 *ts = container_of(chip, struct max7301, chip);
/* First 4 pins are unused in the controller */
offset += 4;
mutex_lock(&ts->lock);
__max7301_set(ts, offset, value);
mutex_unlock(&ts->lock);
}
static int __devinit max7301_probe(struct spi_device *spi)
{
struct max7301 *ts;
struct max7301_platform_data *pdata;
int i, ret;
pdata = spi->dev.platform_data;
if (!pdata || !pdata->base)
return -ENODEV;
/*
* bits_per_word cannot be configured in platform data
*/
spi->bits_per_word = 16;
ret = spi_setup(spi);
if (ret < 0)
return ret;
ts = kzalloc(sizeof(struct max7301), GFP_KERNEL);
if (!ts)
return -ENOMEM;
mutex_init(&ts->lock);
dev_set_drvdata(&spi->dev, ts);
/* Power up the chip and disable IRQ output */
max7301_write(spi, 0x04, 0x01);
ts->spi = spi;
ts->chip.label = DRIVER_NAME,
ts->chip.direction_input = max7301_direction_input;
ts->chip.get = max7301_get;
ts->chip.direction_output = max7301_direction_output;
ts->chip.set = max7301_set;
ts->chip.base = pdata->base;
ts->chip.ngpio = PIN_NUMBER;
ts->chip.can_sleep = 1;
ts->chip.dev = &spi->dev;
ts->chip.owner = THIS_MODULE;
/*
* tristate all pins in hardware and cache the
* register values for later use.
*/
for (i = 1; i < 8; i++) {
int j;
/* 0xAA means input with internal pullup disabled */
max7301_write(spi, 0x08 + i, 0xAA);
ts->port_config[i] = 0xAA;
for (j = 0; j < 4; j++) {
int offset = (i - 1) * 4 + j;
ret = max7301_direction_input(&ts->chip, offset);
if (ret)
goto exit_destroy;
}
}
ret = gpiochip_add(&ts->chip);
if (ret)
goto exit_destroy;
return ret;
exit_destroy:
dev_set_drvdata(&spi->dev, NULL);
mutex_destroy(&ts->lock);
kfree(ts);
return ret;
}
static int max7301_remove(struct spi_device *spi)
{
struct max7301 *ts;
int ret;
ts = dev_get_drvdata(&spi->dev);
if (ts == NULL)
return -ENODEV;
dev_set_drvdata(&spi->dev, NULL);
/* Power down the chip and disable IRQ output */
max7301_write(spi, 0x04, 0x00);
ret = gpiochip_remove(&ts->chip);
if (!ret) {
mutex_destroy(&ts->lock);
kfree(ts);
} else
dev_err(&spi->dev, "Failed to remove the GPIO controller: %d\n",
ret);
return ret;
}
static struct spi_driver max7301_driver = {
.driver = {
.name = DRIVER_NAME,
.owner = THIS_MODULE,
},
.probe = max7301_probe,
.remove = __devexit_p(max7301_remove),
};
static int __init max7301_init(void)
{
return spi_register_driver(&max7301_driver);
}
/* register after spi postcore initcall and before
* subsys initcalls that may rely on these GPIOs
*/
subsys_initcall(max7301_init);
static void __exit max7301_exit(void)
{
spi_unregister_driver(&max7301_driver);
}
module_exit(max7301_exit);
MODULE_AUTHOR("Juergen Beisert");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MAX7301 SPI based GPIO-Expander");
