/*
 *  htc-i2cpld.c
 *  Chip driver for an unknown CPLD chip found on omap850 HTC devices like
 *  the HTC Wizard and HTC Herald.
 *  The cpld is located on the i2c bus and acts as an input/output GPIO
 *  extender.
 *
 *  Copyright (C) 2009 Cory Maccarrone <darkstar6262@gmail.com>
 *
 *  Based on work done in the linwizard project
 *  Copyright (C) 2008-2009 Angelo Arrifano <miknix@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <linux/htcpld.h>
#include <linux/gpio.h>
#include <linux/slab.h>

struct htcpld_chip {
        spinlock_t              lock;

        /* chip info */
        u8                      reset;
        u8                      addr;
        struct device           *dev;
        struct i2c_client       *client;

        /* Output details */
        u8                      cache_out;
        struct gpio_chip        chip_out;

        /* Input details */
        u8                      cache_in;
        struct gpio_chip        chip_in;

        u16                     irqs_enabled;
        uint                    irq_start;
        int                     nirqs;

        unsigned int            flow_type;
        /*
         * Work structure to allow for setting values outside of any
         * possible interrupt context
         */
        struct work_struct set_val_work;
};

struct htcpld_data {
        /* irq info */
        u16                irqs_enabled;
        uint               irq_start;
        int                nirqs;
        uint               chained_irq;
        unsigned int       int_reset_gpio_hi;
        unsigned int       int_reset_gpio_lo;

        /* htcpld info */
        struct htcpld_chip *chip;
        unsigned int       nchips;
};

/* There does not appear to be a way to proactively mask interrupts
 * on the htcpld chip itself.  So, we simply ignore interrupts that
 * aren't desired. */
static void htcpld_mask(struct irq_data *data)
{
        struct htcpld_chip *chip = irq_data_get_irq_chip_data(data);
        chip->irqs_enabled &= ~(1 << (data->irq - chip->irq_start));
        pr_debug("HTCPLD mask %d %04x\n", data->irq, chip->irqs_enabled);
}
static void htcpld_unmask(struct irq_data *data)
{
        struct htcpld_chip *chip = irq_data_get_irq_chip_data(data);
        chip->irqs_enabled |= 1 << (data->irq - chip->irq_start);
        pr_debug("HTCPLD unmask %d %04x\n", data->irq, chip->irqs_enabled);
}

static int htcpld_set_type(struct irq_data *data, unsigned int flags)
{
        struct htcpld_chip *chip = irq_data_get_irq_chip_data(data);

        if (flags & ~IRQ_TYPE_SENSE_MASK)
                return -EINVAL;

        /* We only allow edge triggering */
        if (flags & (IRQ_TYPE_LEVEL_LOW|IRQ_TYPE_LEVEL_HIGH))
                return -EINVAL;

        chip->flow_type = flags;
        return 0;
}

static struct irq_chip htcpld_muxed_chip = {
        .name         = "htcpld",
        .irq_mask     = htcpld_mask,
        .irq_unmask   = htcpld_unmask,
        .irq_set_type = htcpld_set_type,
};

/* To properly dispatch IRQ events, we need to read from the
 * chip.  This is an I2C action that could possibly sleep
 * (which is bad in interrupt context) -- so we use a threaded
 * interrupt handler to get around that.
 */
static irqreturn_t htcpld_handler(int irq, void *dev)
{
        struct htcpld_data *htcpld = dev;
        unsigned int i;
        unsigned long flags;
        int irqpin;

        if (!htcpld) {
                pr_debug("htcpld is null in ISR\n");
                return IRQ_HANDLED;
        }

        /*
         * For each chip, do a read of the chip and trigger any interrupts
         * desired.  The interrupts will be triggered from LSB to MSB (i.e.
         * bit 0 first, then bit 1, etc.)
         *
         * For chips that have no interrupt range specified, just skip 'em.
         */
        for (i = 0; i < htcpld->nchips; i++) {
                struct htcpld_chip *chip = &htcpld->chip[i];
                struct i2c_client *client;
                int val;
                unsigned long uval, old_val;

                if (!chip) {
                        pr_debug("chip %d is null in ISR\n", i);
                        continue;
                }

                if (chip->nirqs == 0)
                        continue;

                client = chip->client;
                if (!client) {
                        pr_debug("client %d is null in ISR\n", i);
                        continue;
                }

                /* Scan the chip */
                val = i2c_smbus_read_byte_data(client, chip->cache_out);
                if (val < 0) {
                        /* Throw a warning and skip this chip */
                        dev_warn(chip->dev, "Unable to read from chip: %d\n",
                                 val);
                        continue;
                }

                uval = (unsigned long)val;

                spin_lock_irqsave(&chip->lock, flags);

                /* Save away the old value so we can compare it */
                old_val = chip->cache_in;

                /* Write the new value */
                chip->cache_in = uval;

                spin_unlock_irqrestore(&chip->lock, flags);

                /*
                 * For each bit in the data (starting at bit 0), trigger
                 * associated interrupts.
                 */
                for (irqpin = 0; irqpin < chip->nirqs; irqpin++) {
                        unsigned oldb, newb, type = chip->flow_type;

                        irq = chip->irq_start + irqpin;

                        /* Run the IRQ handler, but only if the bit value
                         * changed, and the proper flags are set */
                        oldb = (old_val >> irqpin) & 1;
                        newb = (uval >> irqpin) & 1;

                        if ((!oldb && newb && (type & IRQ_TYPE_EDGE_RISING)) ||
                            (oldb && !newb && (type & IRQ_TYPE_EDGE_FALLING))) {
                                pr_debug("fire IRQ %d\n", irqpin);
                                generic_handle_irq(irq);
                        }
                }
        }

        /*
         * In order to continue receiving interrupts, the int_reset_gpio must
         * be asserted.
         */
        if (htcpld->int_reset_gpio_hi)
                gpio_set_value(htcpld->int_reset_gpio_hi, 1);
        if (htcpld->int_reset_gpio_lo)
                gpio_set_value(htcpld->int_reset_gpio_lo, 0);

        return IRQ_HANDLED;
}

/*
 * The GPIO set routines can be called from interrupt context, especially if,
 * for example they're attached to the led-gpio framework and a trigger is
 * enabled.  As such, we declared work above in the htcpld_chip structure,
 * and that work is scheduled in the set routine.  The kernel can then run
 * the I2C functions, which will sleep, in process context.
 */
static void htcpld_chip_set(struct gpio_chip *chip, unsigned offset, int val)
{
        struct i2c_client *client;
        struct htcpld_chip *chip_data = gpiochip_get_data(chip);
        unsigned long flags;

        client = chip_data->client;
        if (!client)
                return;

        spin_lock_irqsave(&chip_data->lock, flags);
        if (val)
                chip_data->cache_out |= (1 << offset);
        else
                chip_data->cache_out &= ~(1 << offset);
        spin_unlock_irqrestore(&chip_data->lock, flags);

        schedule_work(&(chip_data->set_val_work));
}

static void htcpld_chip_set_ni(struct work_struct *work)
{
        struct htcpld_chip *chip_data;
        struct i2c_client *client;

        chip_data = container_of(work, struct htcpld_chip, set_val_work);
        client = chip_data->client;
        i2c_smbus_read_byte_data(client, chip_data->cache_out);
}

static int htcpld_chip_get(struct gpio_chip *chip, unsigned offset)
{
        struct htcpld_chip *chip_data = gpiochip_get_data(chip);
        u8 cache;

        if (!strncmp(chip->label, "htcpld-out", 10)) {
                cache = chip_data->cache_out;
        } else if (!strncmp(chip->label, "htcpld-in", 9)) {
                cache = chip_data->cache_in;
        } else
                return -EINVAL;

        return (cache >> offset) & 1;
}

static int htcpld_direction_output(struct gpio_chip *chip,
                                        unsigned offset, int value)
{
        htcpld_chip_set(chip, offset, value);
        return 0;
}

static int htcpld_direction_input(struct gpio_chip *chip,
                                        unsigned offset)
{
        /*
         * No-op: this function can only be called on the input chip.
         * We do however make sure the offset is within range.
         */
        return (offset < chip->ngpio) ? 0 : -EINVAL;
}

static int htcpld_chip_to_irq(struct gpio_chip *chip, unsigned offset)
{
        struct htcpld_chip *chip_data = gpiochip_get_data(chip);

        if (offset < chip_data->nirqs)
                return chip_data->irq_start + offset;
        else
                return -EINVAL;
}

static void htcpld_chip_reset(struct i2c_client *client)
{
        struct htcpld_chip *chip_data = i2c_get_clientdata(client);
        if (!chip_data)
                return;

        i2c_smbus_read_byte_data(
                client, (chip_data->cache_out = chip_data->reset));
}

static int htcpld_setup_chip_irq(
                struct platform_device *pdev,
                int chip_index)
{
        struct htcpld_data *htcpld;
        struct htcpld_chip *chip;
        unsigned int irq, irq_end;

        /* Get the platform and driver data */
        htcpld = platform_get_drvdata(pdev);
        chip = &htcpld->chip[chip_index];

        /* Setup irq handlers */
        irq_end = chip->irq_start + chip->nirqs;
        for (irq = chip->irq_start; irq < irq_end; irq++) {
                irq_set_chip_and_handler(irq, &htcpld_muxed_chip,
                                         handle_simple_irq);
                irq_set_chip_data(irq, chip);
                irq_clear_status_flags(irq, IRQ_NOREQUEST | IRQ_NOPROBE);
        }

        return 0;
}

static int htcpld_register_chip_i2c(
                struct platform_device *pdev,
                int chip_index)
{
        struct htcpld_data *htcpld;
        struct device *dev = &pdev->dev;
        struct htcpld_core_platform_data *pdata;
        struct htcpld_chip *chip;
        struct htcpld_chip_platform_data *plat_chip_data;
        struct i2c_adapter *adapter;
        struct i2c_client *client;
        struct i2c_board_info info;

        /* Get the platform and driver data */
        pdata = dev_get_platdata(dev);
        htcpld = platform_get_drvdata(pdev);
        chip = &htcpld->chip[chip_index];
        plat_chip_data = &pdata->chip[chip_index];

        adapter = i2c_get_adapter(pdata->i2c_adapter_id);
        if (!adapter) {
                /* Eek, no such I2C adapter!  Bail out. */
                dev_warn(dev, "Chip at i2c address 0x%x: Invalid i2c adapter %d\n",
                         plat_chip_data->addr, pdata->i2c_adapter_id);
                return -ENODEV;
        }

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
                dev_warn(dev, "i2c adapter %d non-functional\n",
                         pdata->i2c_adapter_id);
                return -EINVAL;
        }

        memset(&info, 0, sizeof(struct i2c_board_info));
        info.addr = plat_chip_data->addr;
        strlcpy(info.type, "htcpld-chip", I2C_NAME_SIZE);
        info.platform_data = chip;

        /* Add the I2C device.  This calls the probe() function. */
        client = i2c_new_device(adapter, &info);
        if (!client) {
                /* I2C device registration failed, contineu with the next */
                dev_warn(dev, "Unable to add I2C device for 0x%x\n",
                         plat_chip_data->addr);
                return -ENODEV;
        }

        i2c_set_clientdata(client, chip);
        snprintf(client->name, I2C_NAME_SIZE, "Chip_0x%x", client->addr);
        chip->client = client;

        /* Reset the chip */
        htcpld_chip_reset(client);
        chip->cache_in = i2c_smbus_read_byte_data(client, chip->cache_out);

        return 0;
}

static void htcpld_unregister_chip_i2c(
                struct platform_device *pdev,
                int chip_index)
{
        struct htcpld_data *htcpld;
        struct htcpld_chip *chip;

        /* Get the platform and driver data */
        htcpld = platform_get_drvdata(pdev);
        chip = &htcpld->chip[chip_index];

        if (chip->client)
                i2c_unregister_device(chip->client);
}

static int htcpld_register_chip_gpio(
                struct platform_device *pdev,
                int chip_index)
{
        struct htcpld_data *htcpld;
        struct device *dev = &pdev->dev;
        struct htcpld_core_platform_data *pdata;
        struct htcpld_chip *chip;
        struct htcpld_chip_platform_data *plat_chip_data;
        struct gpio_chip *gpio_chip;
        int ret = 0;

        /* Get the platform and driver data */
        pdata = dev_get_platdata(dev);
        htcpld = platform_get_drvdata(pdev);
        chip = &htcpld->chip[chip_index];
        plat_chip_data = &pdata->chip[chip_index];

        /* Setup the GPIO chips */
        gpio_chip = &(chip->chip_out);
        gpio_chip->label           = "htcpld-out";
        gpio_chip->parent             = dev;
        gpio_chip->owner           = THIS_MODULE;
        gpio_chip->get             = htcpld_chip_get;
        gpio_chip->set             = htcpld_chip_set;
        gpio_chip->direction_input = NULL;
        gpio_chip->direction_output = htcpld_direction_output;
        gpio_chip->base            = plat_chip_data->gpio_out_base;
        gpio_chip->ngpio           = plat_chip_data->num_gpios;

        gpio_chip = &(chip->chip_in);
        gpio_chip->label           = "htcpld-in";
        gpio_chip->parent             = dev;
        gpio_chip->owner           = THIS_MODULE;
        gpio_chip->get             = htcpld_chip_get;
        gpio_chip->set             = NULL;
        gpio_chip->direction_input = htcpld_direction_input;
        gpio_chip->direction_output = NULL;
        gpio_chip->to_irq          = htcpld_chip_to_irq;
        gpio_chip->base            = plat_chip_data->gpio_in_base;
        gpio_chip->ngpio           = plat_chip_data->num_gpios;

        /* Add the GPIO chips */
        ret = gpiochip_add_data(&(chip->chip_out), chip);
        if (ret) {
                dev_warn(dev, "Unable to register output GPIOs for 0x%x: %d\n",
                         plat_chip_data->addr, ret);
                return ret;
        }

        ret = gpiochip_add_data(&(chip->chip_in), chip);
        if (ret) {
                dev_warn(dev, "Unable to register input GPIOs for 0x%x: %d\n",
                         plat_chip_data->addr, ret);
                gpiochip_remove(&(chip->chip_out));
                return ret;
        }

        return 0;
}

static int htcpld_setup_chips(struct platform_device *pdev)
{
        struct htcpld_data *htcpld;
        struct device *dev = &pdev->dev;
        struct htcpld_core_platform_data *pdata;
        int i;

        /* Get the platform and driver data */
        pdata = dev_get_platdata(dev);
        htcpld = platform_get_drvdata(pdev);

        /* Setup each chip's output GPIOs */
        htcpld->nchips = pdata->num_chip;
        htcpld->chip = devm_kzalloc(dev, sizeof(struct htcpld_chip) * htcpld->nchips,
                                    GFP_KERNEL);
        if (!htcpld->chip) {
                dev_warn(dev, "Unable to allocate memory for chips\n");
                return -ENOMEM;
        }

        /* Add the chips as best we can */
        for (i = 0; i < htcpld->nchips; i++) {
                int ret;

                /* Setup the HTCPLD chips */
                htcpld->chip[i].reset = pdata->chip[i].reset;
                htcpld->chip[i].cache_out = pdata->chip[i].reset;
                htcpld->chip[i].cache_in = 0;
                htcpld->chip[i].dev = dev;
                htcpld->chip[i].irq_start = pdata->chip[i].irq_base;
                htcpld->chip[i].nirqs = pdata->chip[i].num_irqs;

                INIT_WORK(&(htcpld->chip[i].set_val_work), &htcpld_chip_set_ni);
                spin_lock_init(&(htcpld->chip[i].lock));

                /* Setup the interrupts for the chip */
                if (htcpld->chained_irq) {
                        ret = htcpld_setup_chip_irq(pdev, i);
                        if (ret)
                                continue;
                }

                /* Register the chip with I2C */
                ret = htcpld_register_chip_i2c(pdev, i);
                if (ret)
                        continue;


                /* Register the chips with the GPIO subsystem */
                ret = htcpld_register_chip_gpio(pdev, i);
                if (ret) {
                        /* Unregister the chip from i2c and continue */
                        htcpld_unregister_chip_i2c(pdev, i);
                        continue;
                }

                dev_info(dev, "Registered chip at 0x%x\n", pdata->chip[i].addr);
        }

        return 0;
}

static int htcpld_core_probe(struct platform_device *pdev)
{
        struct htcpld_data *htcpld;
        struct device *dev = &pdev->dev;
        struct htcpld_core_platform_data *pdata;
        struct resource *res;
        int ret = 0;

        if (!dev)
                return -ENODEV;

        pdata = dev_get_platdata(dev);
        if (!pdata) {
                dev_warn(dev, "Platform data not found for htcpld core!\n");
                return -ENXIO;
        }

        htcpld = devm_kzalloc(dev, sizeof(struct htcpld_data), GFP_KERNEL);
        if (!htcpld)
                return -ENOMEM;

        /* Find chained irq */
        res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (res) {
                int flags;
                htcpld->chained_irq = res->start;

                /* Setup the chained interrupt handler */
                flags = IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING |
                        IRQF_ONESHOT;
                ret = request_threaded_irq(htcpld->chained_irq,
                                           NULL, htcpld_handler,
                                           flags, pdev->name, htcpld);
                if (ret) {
                        dev_warn(dev, "Unable to setup chained irq handler: %d\n", ret);
                        return ret;
                } else
                        device_init_wakeup(dev, 0);
        }

        /* Set the driver data */
        platform_set_drvdata(pdev, htcpld);

        /* Setup the htcpld chips */
        ret = htcpld_setup_chips(pdev);
        if (ret)
                return ret;

        /* Request the GPIO(s) for the int reset and set them up */
        if (pdata->int_reset_gpio_hi) {
                ret = gpio_request(pdata->int_reset_gpio_hi, "htcpld-core");
                if (ret) {
                        /*
                         * If it failed, that sucks, but we can probably
                         * continue on without it.
                         */
                        dev_warn(dev, "Unable to request int_reset_gpio_hi -- interrupts may not work\n");
                        htcpld->int_reset_gpio_hi = 0;
                } else {
                        htcpld->int_reset_gpio_hi = pdata->int_reset_gpio_hi;
                        gpio_set_value(htcpld->int_reset_gpio_hi, 1);
                }
        }

        if (pdata->int_reset_gpio_lo) {
                ret = gpio_request(pdata->int_reset_gpio_lo, "htcpld-core");
                if (ret) {
                        /*
                         * If it failed, that sucks, but we can probably
                         * continue on without it.
                         */
                        dev_warn(dev, "Unable to request int_reset_gpio_lo -- interrupts may not work\n");
                        htcpld->int_reset_gpio_lo = 0;
                } else {
                        htcpld->int_reset_gpio_lo = pdata->int_reset_gpio_lo;
                        gpio_set_value(htcpld->int_reset_gpio_lo, 0);
                }
        }

        dev_info(dev, "Initialized successfully\n");
        return 0;
}

/* The I2C Driver -- used internally */
static const struct i2c_device_id htcpld_chip_id[] = {
        { "htcpld-chip", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, htcpld_chip_id);


static struct i2c_driver htcpld_chip_driver = {
        .driver = {
                .name   = "htcpld-chip",
        },
        .id_table = htcpld_chip_id,
};

/* The Core Driver */
static struct platform_driver htcpld_core_driver = {
        .driver = {
                .name = "i2c-htcpld",
        },
};

static int __init htcpld_core_init(void)
{
        int ret;

        /* Register the I2C Chip driver */
        ret = i2c_add_driver(&htcpld_chip_driver);
        if (ret)
                return ret;

        /* Probe for our chips */
        return platform_driver_probe(&htcpld_core_driver, htcpld_core_probe);
}

static void __exit htcpld_core_exit(void)
{
        i2c_del_driver(&htcpld_chip_driver);
        platform_driver_unregister(&htcpld_core_driver);
}

module_init(htcpld_core_init);
module_exit(htcpld_core_exit);

MODULE_AUTHOR("Cory Maccarrone <darkstar6262@gmail.com>");
MODULE_DESCRIPTION("I2C HTC PLD Driver");
MODULE_LICENSE("GPL");