/**
 * Copyright (C) 2006 Juergen Beisert, Pengutronix
 * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
 * Copyright (C) 2009 Wolfram Sang, 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 MAX7300/1 device is an I2C/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/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/spi/max7301.h>
#include <linux/gpio.h>
#include <linux/slab.h>

/*
 * 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

static int max7301_direction_input(struct gpio_chip *chip, unsigned offset)
{
        struct max7301 *ts = container_of(chip, struct max7301, chip);
        u8 *config;
        u8 offset_bits, pin_config;
        int ret;

        /* First 4 pins are unused in the controller */
        offset += 4;
        offset_bits = (offset & 3) << 1;

        config = &ts->port_config[offset >> 2];

        if (ts->input_pullup_active & BIT(offset))
                pin_config = PIN_CONFIG_IN_PULLUP;
        else
                pin_config = PIN_CONFIG_IN_WO_PULLUP;

        mutex_lock(&ts->lock);

        *config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
                           | (pin_config << offset_bits);

        ret = ts->write(ts->dev, 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 ts->write(ts->dev, 0x20 + offset, 0x01);
        } else {
                ts->out_level &= ~(1 << offset);
                return ts->write(ts->dev, 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;
        u8 offset_bits;
        int ret;

        /* First 4 pins are unused in the controller */
        offset += 4;
        offset_bits = (offset & 3) << 1;

        config = &ts->port_config[offset >> 2];

        mutex_lock(&ts->lock);

        *config = (*config & ~(PIN_CONFIG_MASK << offset_bits))
                           | (PIN_CONFIG_OUT << offset_bits);

        ret = __max7301_set(ts, offset, value);

        if (!ret)
                ret = ts->write(ts->dev, 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) << 1))
                        & PIN_CONFIG_MASK;

        switch (config) {
        case PIN_CONFIG_OUT:
                /* Output: return cached level */
                level =  !!(ts->out_level & (1 << offset));
                break;
        case PIN_CONFIG_IN_WO_PULLUP:
        case PIN_CONFIG_IN_PULLUP:
                /* Input: read out */
                level = ts->read(ts->dev, 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);
}

int __max730x_probe(struct max7301 *ts)
{
        struct device *dev = ts->dev;
        struct max7301_platform_data *pdata;
        int i, ret;

        pdata = dev->platform_data;

        mutex_init(&ts->lock);
        dev_set_drvdata(dev, ts);

        /* Power up the chip and disable IRQ output */
        ts->write(dev, 0x04, 0x01);

        if (pdata) {
                ts->input_pullup_active = pdata->input_pullup_active;
                ts->chip.base = pdata->base;
        } else {
                ts->chip.base = -1;
        }
        ts->chip.label = dev->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.ngpio = PIN_NUMBER;
        ts->chip.can_sleep = 1;
        ts->chip.dev = dev;
        ts->chip.owner = THIS_MODULE;

        /*
         * initialize pullups according to platform data and cache the
         * register values for later use.
         */
        for (i = 1; i < 8; i++) {
                int j;
                /*
                 * initialize port_config with "0xAA", which means
                 * input with internal pullup disabled. This is needed
                 * to avoid writing zeros (in the inner for loop),
                 * which is not allowed according to the datasheet.
                 */
                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(dev, NULL);
        mutex_destroy(&ts->lock);
        return ret;
}
EXPORT_SYMBOL_GPL(__max730x_probe);

int __max730x_remove(struct device *dev)
{
        struct max7301 *ts = dev_get_drvdata(dev);
        int ret;

        if (ts == NULL)
                return -ENODEV;

        dev_set_drvdata(dev, NULL);

        /* Power down the chip and disable IRQ output */
        ts->write(dev, 0x04, 0x00);

        ret = gpiochip_remove(&ts->chip);
        if (!ret) {
                mutex_destroy(&ts->lock);
                kfree(ts);
        } else
                dev_err(dev, "Failed to remove GPIO controller: %d\n", ret);

        return ret;
}
EXPORT_SYMBOL_GPL(__max730x_remove);

MODULE_AUTHOR("Juergen Beisert, Wolfram Sang");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MAX730x GPIO-Expanders, generic parts");