/*
 * Copyright 2007-2008 Extreme Engineering Solutions, Inc.
 *
 * Author: Nate Case <ncase@xes-inc.com>
 *
 * This file is subject to the terms and conditions of version 2 of
 * the GNU General Public License.  See the file COPYING in the main
 * directory of this archive for more details.
 *
 * LED driver for various PCA955x I2C LED drivers
 *
 * Supported devices:
 *
 *      Device          Description             7-bit slave address
 *      ------          -----------             -------------------
 *      PCA9550         2-bit driver            0x60 .. 0x61
 *      PCA9551         8-bit driver            0x60 .. 0x67
 *      PCA9552         16-bit driver           0x60 .. 0x67
 *      PCA9553/01      4-bit driver            0x62
 *      PCA9553/02      4-bit driver            0x63
 *
 * Philips PCA955x LED driver chips follow a register map as shown below:
 *
 *      Control Register                Description
 *      ----------------                -----------
 *      0x0                             Input register 0
 *                                      ..
 *      NUM_INPUT_REGS - 1              Last Input register X
 *
 *      NUM_INPUT_REGS                  Frequency prescaler 0
 *      NUM_INPUT_REGS + 1              PWM register 0
 *      NUM_INPUT_REGS + 2              Frequency prescaler 1
 *      NUM_INPUT_REGS + 3              PWM register 1
 *
 *      NUM_INPUT_REGS + 4              LED selector 0
 *      NUM_INPUT_REGS + 4
 *          + NUM_LED_REGS - 1          Last LED selector
 *
 *  where NUM_INPUT_REGS and NUM_LED_REGS vary depending on how many
 *  bits the chip supports.
 */

#include <linux/module.h>
#include <linux/delay.h>
#include <linux/string.h>
#include <linux/ctype.h>
#include <linux/leds.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/workqueue.h>

/* LED select registers determine the source that drives LED outputs */
#define PCA955X_LS_LED_ON       0x0     /* Output LOW */
#define PCA955X_LS_LED_OFF      0x1     /* Output HI-Z */
#define PCA955X_LS_BLINK0       0x2     /* Blink at PWM0 rate */
#define PCA955X_LS_BLINK1       0x3     /* Blink at PWM1 rate */

enum pca955x_type {
        pca9550,
        pca9551,
        pca9552,
        pca9553,
};

struct pca955x_chipdef {
        int                     bits;
        u8                      slv_addr;       /* 7-bit slave address mask */
        int                     slv_addr_shift; /* Number of bits to ignore */
};

static struct pca955x_chipdef pca955x_chipdefs[] = {
        [pca9550] = {
                .bits           = 2,
                .slv_addr       = /* 110000x */ 0x60,
                .slv_addr_shift = 1,
        },
        [pca9551] = {
                .bits           = 8,
                .slv_addr       = /* 1100xxx */ 0x60,
                .slv_addr_shift = 3,
        },
        [pca9552] = {
                .bits           = 16,
                .slv_addr       = /* 1100xxx */ 0x60,
                .slv_addr_shift = 3,
        },
        [pca9553] = {
                .bits           = 4,
                .slv_addr       = /* 110001x */ 0x62,
                .slv_addr_shift = 1,
        },
};

static const struct i2c_device_id pca955x_id[] = {
        { "pca9550", pca9550 },
        { "pca9551", pca9551 },
        { "pca9552", pca9552 },
        { "pca9553", pca9553 },
        { }
};
MODULE_DEVICE_TABLE(i2c, pca955x_id);

struct pca955x_led {
        struct pca955x_chipdef  *chipdef;
        struct i2c_client       *client;
        struct work_struct      work;
        spinlock_t              lock;
        enum led_brightness     brightness;
        struct led_classdev     led_cdev;
        int                     led_num;        /* 0 .. 15 potentially */
        char                    name[32];
};

/* 8 bits per input register */
static inline int pca95xx_num_input_regs(int bits)
{
        return (bits + 7) / 8;
}

/* 4 bits per LED selector register */
static inline int pca95xx_num_led_regs(int bits)
{
        return (bits + 3)  / 4;
}

/*
 * Return an LED selector register value based on an existing one, with
 * the appropriate 2-bit state value set for the given LED number (0-3).
 */
static inline u8 pca955x_ledsel(u8 oldval, int led_num, int state)
{
        return (oldval & (~(0x3 << (led_num << 1)))) |
                ((state & 0x3) << (led_num << 1));
}

/*
 * Write to frequency prescaler register, used to program the
 * period of the PWM output.  period = (PSCx + 1) / 38
 */
static void pca955x_write_psc(struct i2c_client *client, int n, u8 val)
{
        struct pca955x_led *pca955x = i2c_get_clientdata(client);

        i2c_smbus_write_byte_data(client,
                pca95xx_num_input_regs(pca955x->chipdef->bits) + 2*n,
                val);
}

/*
 * Write to PWM register, which determines the duty cycle of the
 * output.  LED is OFF when the count is less than the value of this
 * register, and ON when it is greater.  If PWMx == 0, LED is always OFF.
 *
 * Duty cycle is (256 - PWMx) / 256
 */
static void pca955x_write_pwm(struct i2c_client *client, int n, u8 val)
{
        struct pca955x_led *pca955x = i2c_get_clientdata(client);

        i2c_smbus_write_byte_data(client,
                pca95xx_num_input_regs(pca955x->chipdef->bits) + 1 + 2*n,
                val);
}

/*
 * Write to LED selector register, which determines the source that
 * drives the LED output.
 */
static void pca955x_write_ls(struct i2c_client *client, int n, u8 val)
{
        struct pca955x_led *pca955x = i2c_get_clientdata(client);

        i2c_smbus_write_byte_data(client,
                pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n,
                val);
}

/*
 * Read the LED selector register, which determines the source that
 * drives the LED output.
 */
static u8 pca955x_read_ls(struct i2c_client *client, int n)
{
        struct pca955x_led *pca955x = i2c_get_clientdata(client);

        return (u8) i2c_smbus_read_byte_data(client,
                pca95xx_num_input_regs(pca955x->chipdef->bits) + 4 + n);
}

static void pca955x_led_work(struct work_struct *work)
{
        struct pca955x_led *pca955x;
        u8 ls;
        int chip_ls;    /* which LSx to use (0-3 potentially) */
        int ls_led;     /* which set of bits within LSx to use (0-3) */

        pca955x = container_of(work, struct pca955x_led, work);
        chip_ls = pca955x->led_num / 4;
        ls_led = pca955x->led_num % 4;

        ls = pca955x_read_ls(pca955x->client, chip_ls);

        switch (pca955x->brightness) {
        case LED_FULL:
                ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_ON);
                break;
        case LED_OFF:
                ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_LED_OFF);
                break;
        case LED_HALF:
                ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK0);
                break;
        default:
                /*
                 * Use PWM1 for all other values.  This has the unwanted
                 * side effect of making all LEDs on the chip share the
                 * same brightness level if set to a value other than
                 * OFF, HALF, or FULL.  But, this is probably better than
                 * just turning off for all other values.
                 */
                pca955x_write_pwm(pca955x->client, 1, 255-pca955x->brightness);
                ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
                break;
        }

        pca955x_write_ls(pca955x->client, chip_ls, ls);
}

static void pca955x_led_set(struct led_classdev *led_cdev, enum led_brightness value)
{
        struct pca955x_led *pca955x;

        pca955x = container_of(led_cdev, struct pca955x_led, led_cdev);

        spin_lock(&pca955x->lock);
        pca955x->brightness = value;

        /*
         * Must use workqueue for the actual I/O since I2C operations
         * can sleep.
         */
        schedule_work(&pca955x->work);

        spin_unlock(&pca955x->lock);
}

static int __devinit pca955x_probe(struct i2c_client *client,
                                        const struct i2c_device_id *id)
{
        struct pca955x_led *pca955x;
        struct pca955x_chipdef *chip;
        struct i2c_adapter *adapter;
        struct led_platform_data *pdata;
        int i, err;

        chip = &pca955x_chipdefs[id->driver_data];
        adapter = to_i2c_adapter(client->dev.parent);
        pdata = client->dev.platform_data;

        /* Make sure the slave address / chip type combo given is possible */
        if ((client->addr & ~((1 << chip->slv_addr_shift) - 1)) !=
            chip->slv_addr) {
                dev_err(&client->dev, "invalid slave address %02x\n",
                                client->addr);
                return -ENODEV;
        }

        printk(KERN_INFO "leds-pca955x: Using %s %d-bit LED driver at "
                        "slave address 0x%02x\n",
                        id->name, chip->bits, client->addr);

        if (!i2c_check_functionality(adapter, I2C_FUNC_I2C))
                return -EIO;

        if (pdata) {
                if (pdata->num_leds != chip->bits) {
                        dev_err(&client->dev, "board info claims %d LEDs"
                                        " on a %d-bit chip\n",
                                        pdata->num_leds, chip->bits);
                        return -ENODEV;
                }
        }

        pca955x = kzalloc(sizeof(*pca955x) * chip->bits, GFP_KERNEL);
        if (!pca955x)
                return -ENOMEM;

        i2c_set_clientdata(client, pca955x);

        for (i = 0; i < chip->bits; i++) {
                pca955x[i].chipdef = chip;
                pca955x[i].client = client;
                pca955x[i].led_num = i;

                /* Platform data can specify LED names and default triggers */
                if (pdata) {
                        if (pdata->leds[i].name)
                                snprintf(pca955x[i].name,
                                         sizeof(pca955x[i].name), "pca955x:%s",
                                         pdata->leds[i].name);
                        if (pdata->leds[i].default_trigger)
                                pca955x[i].led_cdev.default_trigger =
                                        pdata->leds[i].default_trigger;
                } else {
                        snprintf(pca955x[i].name, sizeof(pca955x[i].name),
                                 "pca955x:%d", i);
                }

                spin_lock_init(&pca955x[i].lock);

                pca955x[i].led_cdev.name = pca955x[i].name;
                pca955x[i].led_cdev.brightness_set = pca955x_led_set;

                INIT_WORK(&pca955x[i].work, pca955x_led_work);

                err = led_classdev_register(&client->dev, &pca955x[i].led_cdev);
                if (err < 0)
                        goto exit;
        }

        /* Turn off LEDs */
        for (i = 0; i < pca95xx_num_led_regs(chip->bits); i++)
                pca955x_write_ls(client, i, 0x55);

        /* PWM0 is used for half brightness or 50% duty cycle */
        pca955x_write_pwm(client, 0, 255-LED_HALF);

        /* PWM1 is used for variable brightness, default to OFF */
        pca955x_write_pwm(client, 1, 0);

        /* Set to fast frequency so we do not see flashing */
        pca955x_write_psc(client, 0, 0);
        pca955x_write_psc(client, 1, 0);

        return 0;

exit:
        while (i--) {
                led_classdev_unregister(&pca955x[i].led_cdev);
                cancel_work_sync(&pca955x[i].work);
        }

        kfree(pca955x);
        i2c_set_clientdata(client, NULL);

        return err;
}

static int __devexit pca955x_remove(struct i2c_client *client)
{
        struct pca955x_led *pca955x = i2c_get_clientdata(client);
        int i;

        for (i = 0; i < pca955x->chipdef->bits; i++) {
                led_classdev_unregister(&pca955x[i].led_cdev);
                cancel_work_sync(&pca955x[i].work);
        }

        kfree(pca955x);
        i2c_set_clientdata(client, NULL);

        return 0;
}

static struct i2c_driver pca955x_driver = {
        .driver = {
                .name   = "leds-pca955x",
                .owner  = THIS_MODULE,
        },
        .probe  = pca955x_probe,
        .remove = __devexit_p(pca955x_remove),
        .id_table = pca955x_id,
};

static int __init pca955x_leds_init(void)
{
        return i2c_add_driver(&pca955x_driver);
}

static void __exit pca955x_leds_exit(void)
{
        i2c_del_driver(&pca955x_driver);
}

module_init(pca955x_leds_init);
module_exit(pca955x_leds_exit);

MODULE_AUTHOR("Nate Case <ncase@xes-inc.com>");
MODULE_DESCRIPTION("PCA955x LED driver");
MODULE_LICENSE("GPL v2");