leds-pca955x.c

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/*
 * Copyright 2007-2008 Extreme Engineering Solutions, Inc.
 *
 * Author: Nate Case <[email protected]>
 *
 * 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>
#include <linux/slab.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 {
    struct mutex lock;
    struct pca955x_led *leds;
    struct pca955x_chipdef  *chipdef;
    struct i2c_client   *client;
};

struct pca955x_led {
    struct pca955x  *pca955x;
    struct work_struct  work;
    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 *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 *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 *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 *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_led;
    struct pca955x *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_led = container_of(work, struct pca955x_led, work);
    pca955x = pca955x_led->pca955x;

    chip_ls = pca955x_led->led_num / 4;
    ls_led = pca955x_led->led_num % 4;

    mutex_lock(&pca955x->lock);

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

    switch (pca955x_led->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_led->brightness);
        ls = pca955x_ledsel(ls, ls_led, PCA955X_LS_BLINK1);
        break;
    }

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

    mutex_unlock(&pca955x->lock);
}

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);

    pca955x->brightness = value;

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

static int __devinit pca955x_probe(struct i2c_client *client,
                    const struct i2c_device_id *id)
{
    struct pca955x *pca955x;
    struct pca955x_led *pca955x_led;
    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 = devm_kzalloc(&client->dev, sizeof(*pca955x), GFP_KERNEL);
    if (!pca955x)
        return -ENOMEM;

    pca955x->leds = devm_kzalloc(&client->dev,
            sizeof(*pca955x_led) * chip->bits, GFP_KERNEL);
    if (!pca955x->leds)
        return -ENOMEM;

    i2c_set_clientdata(client, pca955x);

    mutex_init(&pca955x->lock);
    pca955x->client = client;
    pca955x->chipdef = chip;

    for (i = 0; i < chip->bits; i++) {
        pca955x_led = &pca955x->leds[i];
        pca955x_led->led_num = i;
        pca955x_led->pca955x = pca955x;

        /* Platform data can specify LED names and default triggers */
        if (pdata) {
            if (pdata->leds[i].name)
                snprintf(pca955x_led->name,
                    sizeof(pca955x_led->name), "pca955x:%s",
                    pdata->leds[i].name);
            if (pdata->leds[i].default_trigger)
                pca955x_led->led_cdev.default_trigger =
                    pdata->leds[i].default_trigger;
        } else {
            snprintf(pca955x_led->name, sizeof(pca955x_led->name),
                 "pca955x:%d", i);
        }

        pca955x_led->led_cdev.name = pca955x_led->name;
        pca955x_led->led_cdev.brightness_set = pca955x_led_set;

        INIT_WORK(&pca955x_led->work, pca955x_led_work);

        err = led_classdev_register(&client->dev,
                    &pca955x_led->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->leds[i].led_cdev);
        cancel_work_sync(&pca955x->leds[i].work);
    }

    return err;
}

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

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

    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,
};

module_i2c_driver(pca955x_driver);

MODULE_AUTHOR("Nate Case <[email protected]>");
MODULE_DESCRIPTION("PCA955x LED driver");
MODULE_LICENSE("GPL v2");