
/*
 *  lm3695_bl.c - Linux kernel module for National Semiconductor
 *                LM3695 backlight driver
 *
 *  Copyright (C) 2014 Nest Labs, Inc
 *
 *  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.
 *
 *
 * Required properties:
 *	compatible : should be "national,lm3695
 *  reg : i2c slave address (0x63)
 *	enable-gpio : hardware enable gpio.
 *
 * Optional properties:
 *	max-brightness : max current allowed through each channel.
 *		iLED = 50uA x 1.003040572^brightness. Defaults to 2047
 *	default-brightness : Current set on driver probe. defaults to
 *		max-brigtness/2
 *	ramp-rate : time in microseconds between brightness level steps
 *		during ramping. Defaults to 500. 0 means no ramping.
 *	clock-divider : 0-9, number of dividers to apply to 62.5kHz
 *		dithering clk. e.g. 3 = (2^3) divider = 7.8khz
 *	single-string : (bool) use only string 1
 *	boost-freq : (bool) double boost switcher freqency from 500kHz to 1MHz
 * 	freq-shift : (bool) shift boost and dithering freq by -12%.
 *	high-voltage : (bool) Use 21v OVP instead of 16v OVP
 *
 *	example:
 *
 *	lm3695@63{
 *		compatible= "national,lm3695";
 *		reg = <0x68>;
 *		max-brightness = <2047>;
 *		default-brightness = <2000>;
 *		single-string;
 *		ramp-rate = <4000>;
 *		enable-gpio = <&gpio2 14 GPIO_ACTIVE_HIGH>;
 *	}
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/backlight.h>
#include <linux/i2c.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_gpio.h>

#define LM3695_DEV "lcd-backlight"
#define LM3695_NAME "lm3695_bl"

#define LM3695_MAX_BRIGHTNESS	((1 << 11) - 1)
#define MICROSEC_PER_MILLISEC	(1000)

#define LM3695_GEN_PURPOSE_REG			0x10
#define LM3695_BOOST_FREQ_SHIFT_M		(1<<6)
#define LM3695_BOOST_FREQ_SELECT_M		(1<<5)
#define LM3695_OVP_SELECT_M				(1<<4)
#define LM3695_STRING_MODE_M			(1<<3)
#define LM3695_BRIGHTNESS_REG_EN_M		(1<<2)
#define LM3695_RAMP_DISABLE_M			(1<<1)
#define LM3695_CHIP_EN_M				(1<<0)

#define LM3695_DITHER_FREQ_REG			0x11
#define LM3695_DITHER_FREQ_DIV_M		0b1111

#define LM3695_RAMP_RATE_REG			0x12
#define LM3695_RAMP_RATE_0_MS			0b1111
#define LM3695_RAMP_RATE_0_125_MS		0b0000
#define LM3695_RAMP_RATE_0_252_MS		0b0001
#define LM3695_RAMP_RATE_0_5_MS			0b0010
#define LM3695_RAMP_RATE_1_MS			0b0011
#define LM3695_RAMP_RATE_2_MS			0b0100
#define LM3695_RAMP_RATE_4_MS			0b0101
#define LM3695_RAMP_RATE_8_MS			0b0110
#define LM3695_RAMP_RATE_16_MS			0b0111
#define LM3695_RAMP_RATE_32_MS			0b1000
#define LM3695_RAMP_RATE_64_MS			0b1001
#define LM3695_RAMP_RATE_128_MS			0b1010

static const int rates[] = {0, 125, 252, 500, 1000, 2000, 4000, 8000, 16000, 32000, 64000, 128000};

#define LM3695_BRIGHTNESS_L_REG			0x13
#define LM3695_BRIGHTNESS_L_M			0b111
#define LM3695_BRIGHTNESS_L_O			0
#define LM3695_BRIGHTNESS_L_S(x)		(((x) & LM3695_BRIGHTNESS_L_M) >> LM3695_BRIGHTNESS_L_O)

#define LM3695_BRIGHTNESS_H_REG			0x14
#define LM3695_BRIGHTNESS_H_M			0xFF
#define LM3695_BRIGHTNESS_H_O			3
#define LM3695_BRIGHTNESS_H_S(x)		((((x) >> LM3695_BRIGHTNESS_H_O )& LM3695_BRIGHTNESS_H_M))

int default_brightness = 0;
module_param(default_brightness, int, 0664);
MODULE_PARM_DESC(default_brightness, "default brightness to ramp up to at probe");

struct lm3695_data{
	struct i2c_client *client;
	int max_current;
	int hwen_gpio;
	uint16_t max_brightness;
	uint16_t default_brightness;
	uint16_t current_brightness;
	uint16_t next_brightness;
	uint8_t ramp_rise_rate;
	uint8_t ramp_fall_rate;
	uint8_t dither_freq;
	bool	boost_freq;
	bool	boost_shift;
	bool	single_string;
	bool	high_voltage;
	bool	enabled;
};

static ssize_t store_ramp_time(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t len);

static ssize_t show_ramp_time(struct device *dev,
				struct device_attribute *attr, char *buf);

DEVICE_ATTR(ramp_rise_time, S_IRUGO | S_IWUSR, show_ramp_time, store_ramp_time);
DEVICE_ATTR(ramp_fall_time, S_IRUGO | S_IWUSR, show_ramp_time, store_ramp_time);

static struct attribute *lm3695_bl_attributes[] = {
	&dev_attr_ramp_rise_time.attr,
	&dev_attr_ramp_fall_time.attr,
	NULL
};

static struct attribute_group lm3695_bl_attribute_group = {
	.attrs		= lm3695_bl_attributes
};

/*
 *Converts a full ramp transition time in milliseconds to a ramp rate.
 *
 *e.g. 1000 msec ramp: 1000 msec / 2048 ticks =  .488 ticks/msec
 *   which is then rounded to the closest tick rate that will
 *   complete the transition in AT LEAST "time" milliseconds.
 */

uint8_t lm3695_time_to_ramp_rate(uint32_t time)
{
	uint8_t rate;

	uint32_t usec_rate = ( (time*MICROSEC_PER_MILLISEC) / LM3695_MAX_BRIGHTNESS);

	switch (usec_rate) {
	case 0:
		rate = LM3695_RAMP_RATE_0_MS;
		break;
	case 1 ... 125:
		rate = LM3695_RAMP_RATE_0_125_MS;
		break;
	case 126 ... 252:
		rate = LM3695_RAMP_RATE_0_252_MS;
		break;
	case 253 ... 500:
		rate = LM3695_RAMP_RATE_0_5_MS;
		break;
	case 501 ... 1000:
		rate = LM3695_RAMP_RATE_1_MS;
		break;
	case 1001 ... 2000:
		rate = LM3695_RAMP_RATE_2_MS;
		break;
	case 2001 ... 4000:
		rate = LM3695_RAMP_RATE_4_MS;
		break;
	case 4001 ... 8000:
		rate = LM3695_RAMP_RATE_8_MS;
		break;
	case 8001 ... 16000:
		rate = LM3695_RAMP_RATE_16_MS;
		break;
	case 16001 ... 32000:
		rate = LM3695_RAMP_RATE_32_MS;
		break;
	case 32001 ... 64000:
		rate = LM3695_RAMP_RATE_64_MS;
		break;
	default:
		rate = LM3695_RAMP_RATE_128_MS;
	}
	return rate;
}

static ssize_t store_ramp_time(struct device *dev,
					struct device_attribute *attr,
					const char *buf, size_t len)
{
	struct backlight_device *bl = to_backlight_device(dev);
	struct lm3695_data *drvdata = bl_get_data(bl);

	unsigned long time;

	if (kstrtoul(buf, 0, &time))
		return -EINVAL;

	dev_info(dev, "Setting %s to %ld msec", attr->attr.name, time);

	if (attr == &dev_attr_ramp_rise_time)
		drvdata->ramp_rise_rate = lm3695_time_to_ramp_rate(time);
	else if (attr == &dev_attr_ramp_fall_time)
		drvdata->ramp_fall_rate = lm3695_time_to_ramp_rate(time);
	else
		return -EINVAL;

	return len;
}

/*
 *Returns ramp time in milliseconds for a full transition.
 *
 *e.g. 4 msec/tick rate: 4000 usec * 2048 = 8192 msec
 *
 */

static ssize_t show_ramp_time(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	struct backlight_device *bl = to_backlight_device(dev);
	struct lm3695_data *drvdata = bl_get_data(bl);

	uint8_t value;

	if (attr == &dev_attr_ramp_rise_time)
		value = drvdata->ramp_rise_rate;
	else if (attr == &dev_attr_ramp_fall_time)
		value = drvdata->ramp_fall_rate;
	else
		return -EINVAL;

	if (value == LM3695_RAMP_RATE_0_MS)
		value = 0;
	else
		value += 1;

	return sprintf(buf, "%d\n", (LM3695_MAX_BRIGHTNESS*rates[value])/MICROSEC_PER_MILLISEC);
}


int lm3695_configure_device(struct lm3695_data *drvdata, bool enable)
{
	uint8_t data;
	uint8_t rate;
	/*send default data to chip*/
	if (enable)
	{
		if (drvdata->next_brightness < drvdata->current_brightness)
			rate = drvdata->ramp_fall_rate;
		else
			rate = drvdata->ramp_rise_rate;

		gpio_set_value(drvdata->hwen_gpio, 1);
		drvdata->enabled = true;
		data = LM3695_CHIP_EN_M;
		if (drvdata->boost_freq)
			data |= LM3695_BOOST_FREQ_SELECT_M;
		if (!drvdata->boost_shift) /*default to boost*/
			data |= LM3695_BOOST_FREQ_SHIFT_M;
		if (rate == LM3695_RAMP_RATE_0_MS)
			data |= LM3695_RAMP_DISABLE_M;
		if (drvdata->single_string)
			data |= LM3695_STRING_MODE_M;
		if (drvdata->high_voltage)
			data |= LM3695_OVP_SELECT_M;
		data |= LM3695_BRIGHTNESS_REG_EN_M;

		i2c_smbus_write_byte_data(drvdata->client, LM3695_GEN_PURPOSE_REG, data);

		data = drvdata->dither_freq;
		i2c_smbus_write_byte_data(drvdata->client, LM3695_DITHER_FREQ_REG, data);

		data = rate;
		i2c_smbus_write_byte_data(drvdata->client, LM3695_RAMP_RATE_REG, data);
	} else {
		if (drvdata->enabled)
		{
			data = 0;
			i2c_smbus_write_byte_data(drvdata->client, LM3695_GEN_PURPOSE_REG, data);
			gpio_set_value(drvdata->hwen_gpio, 0);
			drvdata->enabled = false;
		}
	}
	return 0;
}

int lm3695_update_status(struct backlight_device * bl)
{
	struct lm3695_data *drvdata = bl_get_data(bl);
	bool enabled = 1;
	drvdata->next_brightness = bl->props.brightness;

	if (drvdata->next_brightness > drvdata->max_brightness)
		drvdata->next_brightness = drvdata->max_brightness;

	if (bl->props.power != FB_BLANK_UNBLANK) {
		enabled = 0;
	}

	if (bl->props.fb_blank != FB_BLANK_UNBLANK) {
		enabled = 0;
	}

	lm3695_configure_device(drvdata, enabled);

	i2c_smbus_write_byte_data(drvdata->client, LM3695_BRIGHTNESS_L_REG,
		LM3695_BRIGHTNESS_L_S(drvdata->next_brightness));
	i2c_smbus_write_byte_data(drvdata->client, LM3695_BRIGHTNESS_H_REG,
		LM3695_BRIGHTNESS_H_S(drvdata->next_brightness));

	drvdata->current_brightness = drvdata->next_brightness;

	return 0;
}
int lm3695_get_brightness(struct backlight_device *bl)
{
	return bl->props.brightness;
}


static struct backlight_ops lm3695_backlight_ops = {
	.update_status	= lm3695_update_status,
	.get_brightness	= lm3695_get_brightness,
};


int lm3695_get_devtree_pdata(struct i2c_client *client, struct lm3695_data *drvdata){

	const int *prop;
	const char *fb_dev;
	int retval = 0;

	prop = of_get_property(client->dev.of_node, "max-brightness", NULL);
	drvdata->max_brightness = prop ? (be32_to_cpu(*prop)) : LM3695_MAX_BRIGHTNESS;

	prop = of_get_property(client->dev.of_node, "default-brightness", NULL);
	drvdata->default_brightness = prop ? (be32_to_cpu(*prop)) : drvdata->max_brightness / 2;
	drvdata->current_brightness = drvdata->default_brightness;
	drvdata->next_brightness = drvdata->default_brightness;

	retval = of_property_read_string(client->dev.of_node, "fb-device", &fb_dev);
	if (!retval)
	{
		if(driver_find(fb_dev, &platform_bus_type) == NULL)
		{
			dev_warn(&client->dev, "Could not find %s driver\n", fb_dev);
			retval = -EPROBE_DEFER;
			goto done;
		}
	}

	if(default_brightness != 0)
	{
		/*override default brightness parameter if uboot has one for us*/
		drvdata->default_brightness = default_brightness;
		dev_info(&client->dev, "Using cmdline parameter %d for brightness", default_brightness);
	}

	drvdata->hwen_gpio = of_get_named_gpio(client->dev.of_node, "enable-gpio", 0);

	prop = of_get_property(client->dev.of_node, "ramp-rise-time", NULL);
	if (prop)
	{
		drvdata->ramp_rise_rate = lm3695_time_to_ramp_rate(be32_to_cpu(*prop));
	}
	prop = of_get_property(client->dev.of_node, "ramp-fall-time", NULL);
	if (prop)
	{
		drvdata->ramp_fall_rate = lm3695_time_to_ramp_rate(be32_to_cpu(*prop));
	}
	else
	{
		drvdata->ramp_rise_rate = LM3695_RAMP_RATE_0_MS;
		drvdata->ramp_fall_rate = LM3695_RAMP_RATE_0_MS;
	}

	prop = of_get_property(client->dev.of_node, "clock-divider", NULL);
	if (prop && (be32_to_cpu(*prop) <= 0b1001) && (*prop >= 0))
	{
		drvdata->dither_freq = be32_to_cpu(*prop);
	}
	else
	{
		drvdata->dither_freq = 0b11;
	}

	drvdata->boost_freq = of_property_read_bool(client->dev.of_node, "boost-freq");
	drvdata->boost_shift = of_property_read_bool(client->dev.of_node, "freq-shift");
	drvdata->single_string = of_property_read_bool(client->dev.of_node, "single-string");
	drvdata->high_voltage = of_property_read_bool(client->dev.of_node, "high-voltage");

done:
	return retval;
}

static int lm3695_probe(struct i2c_client *client,
		const struct i2c_device_id *device)
{

	struct lm3695_data *drvdata;
	struct platform_device *pdev = to_platform_device(&client->dev);
	struct backlight_device *bl;
	struct backlight_properties props;
	int status;
	drvdata = devm_kzalloc(&client->dev,sizeof(struct lm3695_data), GFP_KERNEL);

	status = lm3695_get_devtree_pdata(client, drvdata);
	if (status)
	{
		goto cleanup;
	}

	drvdata->client = client;

	i2c_set_clientdata(client, drvdata);

	status = devm_gpio_request_one(&client->dev, drvdata->hwen_gpio, GPIOF_OUT_INIT_LOW, "lm3695 enable");
	if (status)
	{
		dev_err(&client->dev, "Could not request GPIO %u: %d\n", drvdata->hwen_gpio, status);
		goto cleanup;
	}

	drvdata->enabled = false;

	memset(&props, 0, sizeof(struct backlight_properties));
	props.max_brightness = LM3695_MAX_BRIGHTNESS;
	props.type = BACKLIGHT_FIRMWARE;

	bl = backlight_device_register(dev_name(&client->dev), &client->dev,
			drvdata, &lm3695_backlight_ops, &props);

	if (IS_ERR(bl))
	{
		dev_err(&client->dev, "Could not register bl: %ld\n", PTR_ERR(bl));
		goto cleanup;
	}

	status = sysfs_create_group(&bl->dev.kobj, &lm3695_bl_attribute_group);
	if (status < 0) {
		dev_err(&pdev->dev, "failed to create sysfs attributes\n");
		goto unregister;
	}


	bl->props.max_brightness = drvdata->max_brightness;
	bl->props.brightness = drvdata->default_brightness;

	backlight_update_status(bl);

	platform_set_drvdata(pdev, bl);

	return 0;
unregister:
	backlight_device_unregister(bl);

cleanup:
	return status;

}

static int lm3695_remove(struct i2c_client *client)
{
	struct platform_device *pdev = to_platform_device(&client->dev);
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct lm3695_data *drvdata = bl_get_data(bl);

	lm3695_configure_device(drvdata, 0);
	backlight_device_unregister(bl);
	sysfs_remove_group(&bl->dev.kobj, &lm3695_bl_attribute_group);

	return 0;
}

static void lm3695_shutdown(struct i2c_client *client)
{
	struct platform_device *pdev = to_platform_device(&client->dev);
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct lm3695_data *drvdata = bl_get_data(bl);

	lm3695_configure_device(drvdata, 0);

}

static int lm3695_suspend(struct device *dev){
	struct platform_device *pdev = to_platform_device(dev);
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct lm3695_data *drvdata = bl_get_data(bl);

	lm3695_configure_device(drvdata, 0);
	return 0;
}

static int lm3695_resume(struct device *dev){
	struct platform_device *pdev = to_platform_device(dev);
	struct backlight_device *bl = platform_get_drvdata(pdev);

	backlight_update_status(bl);
	return 0;
}

static const struct i2c_device_id lm3695_id[] = {
	{LM3695_NAME, 0},
	{}
};
MODULE_DEVICE_TABLE(i2c, lm3695_id);

static struct dev_pm_ops lm3695_pm_ops = {
	.suspend = lm3695_suspend,
	.resume = lm3695_resume,
};

#ifdef CONFIG_OF
static const struct of_device_id of_lm3695_bl_match[] = {
	{ .compatible = "national,lm3695", },
	{},
};
#endif

MODULE_DEVICE_TABLE(of, of_lm3695_bl_match);

static struct i2c_driver lm3695_i2c_driver = {
	.probe = lm3695_probe,
	.remove = lm3695_remove,
	.id_table = lm3695_id,
	.shutdown = lm3695_shutdown,
	.driver = {
		.name = LM3695_NAME,
		.owner = THIS_MODULE,
		.pm = &lm3695_pm_ops,
		.of_match_table = of_match_ptr(of_lm3695_bl_match),
	},

};

static int __init lm3695_init(void)
{
	return i2c_add_driver(&lm3695_i2c_driver);
}

static void __exit lm3695_exit(void)
{
	i2c_del_driver(&lm3695_i2c_driver);
}


module_init(lm3695_init);
module_exit(lm3695_exit);

MODULE_DESCRIPTION("i2c driver for LM3695 backlight driver");
MODULE_LICENSE("GPLv2");
MODULE_AUTHOR("Andrew LeCain<alecain@nestlabs.com>");