backlight: new backlight driver for LP855x devices

THis driver supports TI LP8550/LP8551/LP8552/LP8553/LP8556 backlight
devices.

The brightness can be controlled by the I2C or PWM input. The lp855x
driver provides both modes. For the PWM control, pwm-specific functions
can be defined in the platform data. And some information can be read
via the sysfs(lp855x device attributes).

For details, please refer to Documentation/backlight/lp855x-driver.txt.

[[e-mail]: add missing mutex_unlock in lp855x_read_byte() error path]
[[e-mail]: check platform data in lp855x_probe()]
[[e-mail]: small cleanups]
[[e-mail]: silence a compiler warning]
[[e-mail]: use id->driver_data to differentiate lp855x chips]
[[e-mail]: simplify boolean return expression]
Signed-off-by: Milo(Woogyom) Kim <[e-mail]>
Signed-off-by: Axel Lin <[e-mail]>
Signed-off-by: Dan Carpenter <[e-mail]>
Cc: Richard Purdie <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/backlight/lp855x-driver.txt

···
+Kernel driver lp855x
+====================
+
+Backlight driver for LP855x ICs
+
+Supported chips:
+	Texas Instruments LP8550, LP8551, LP8552, LP8553 and LP8556
+
+Author: Milo(Woogyom) Kim <[e-mail]>
+
+Description
+-----------
+
+* Brightness control
+
+Brightness can be controlled by the pwm input or the i2c command.
+The lp855x driver supports both cases.
+
+* Device attributes
+
+1) bl_ctl_mode
+Backlight control mode.
+Value : pwm based or register based
+
+2) chip_id
+The lp855x chip id.
+Value : lp8550/lp8551/lp8552/lp8553/lp8556
+
+Platform data for lp855x
+------------------------
+
+For supporting platform specific data, the lp855x platform data can be used.
+
+* name : Backlight driver name. If it is not defined, default name is set.
+* mode : Brightness control mode. PWM or register based.
+* device_control : Value of DEVICE CONTROL register.
+* initial_brightness : Initial value of backlight brightness.
+* pwm_data : Platform specific pwm generation functions.
+	     Only valid when brightness is pwm input mode.
+	     Functions should be implemented by PWM driver.
+	     - pwm_set_intensity() : set duty of PWM
+	     - pwm_get_intensity() : get current duty of PWM
+* load_new_rom_data :
+	0 : use default configuration data
+	1 : update values of eeprom or eprom registers on loading driver
+* size_program : Total size of lp855x_rom_data.
+* rom_data : List of new eeprom/eprom registers.
+
+example 1) lp8552 platform data : i2c register mode with new eeprom data
+
+#define EEPROM_A5_ADDR	0xA5
+#define EEPROM_A5_VAL	0x4f	/* EN_VSYNC=0 */
+
+static struct lp855x_rom_data lp8552_eeprom_arr[] = {
+	{EEPROM_A5_ADDR, EEPROM_A5_VAL},
+};
+
+static struct lp855x_platform_data lp8552_pdata = {
+	.name = "lcd-bl",
+	.mode = REGISTER_BASED,
+	.device_control = I2C_CONFIG(LP8552),
+	.initial_brightness = INITIAL_BRT,
+	.load_new_rom_data = 1,
+	.size_program = ARRAY_SIZE(lp8552_eeprom_arr),
+	.rom_data = lp8552_eeprom_arr,
+};
+
+example 2) lp8556 platform data : pwm input mode with default rom data
+
+static struct lp855x_platform_data lp8556_pdata = {
+	.mode = PWM_BASED,
+	.device_control = PWM_CONFIG(LP8556),
+	.initial_brightness = INITIAL_BRT,
+	.pwm_data = {
+		     .pwm_set_intensity = platform_pwm_set_intensity,
+		     .pwm_get_intensity = platform_pwm_get_intensity,
+		     },
+};

drivers/video/backlight/Kconfig

···
 	  If you have a AnalogicTech AAT2870 say Y to enable the
 	  backlight driver.
 
+config BACKLIGHT_LP855X
+	tristate "Backlight driver for TI LP855X"
+	depends on BACKLIGHT_CLASS_DEVICE && I2C
+	help
+	  This supports TI LP8550, LP8551, LP8552, LP8553 and LP8556
+	  backlight driver.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endif # BACKLIGHT_LCD_SUPPORT

drivers/video/backlight/Makefile

···
 obj-$(CONFIG_BACKLIGHT_HP700)	+= jornada720_bl.o
 obj-$(CONFIG_BACKLIGHT_HP680)	+= hp680_bl.o
 obj-$(CONFIG_BACKLIGHT_LOCOMO)	+= locomolcd.o
+obj-$(CONFIG_BACKLIGHT_LP855X)	+= lp855x_bl.o
 obj-$(CONFIG_BACKLIGHT_OMAP1)	+= omap1_bl.o
 obj-$(CONFIG_BACKLIGHT_PROGEAR) += progear_bl.o
 obj-$(CONFIG_BACKLIGHT_CARILLO_RANCH) += cr_bllcd.o

drivers/video/backlight/lp855x_bl.c

···
+/*
+ * TI LP855x Backlight Driver
+ *
+ *			Copyright (C) 2011 Texas Instruments
+ *
+ * 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.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/lp855x.h>
+
+/* Registers */
+#define BRIGHTNESS_CTRL		(0x00)
+#define DEVICE_CTRL		(0x01)
+
+#define BUF_SIZE		20
+#define DEFAULT_BL_NAME		"lcd-backlight"
+#define MAX_BRIGHTNESS		255
+
+struct lp855x {
+	const char *chipname;
+	enum lp855x_chip_id chip_id;
+	struct i2c_client *client;
+	struct backlight_device *bl;
+	struct device *dev;
+	struct mutex xfer_lock;
+	struct lp855x_platform_data *pdata;
+};
+
+static int lp855x_read_byte(struct lp855x *lp, u8 reg, u8 *data)
+{
+	int ret;
+
+	mutex_lock(&lp->xfer_lock);
+	ret = i2c_smbus_read_byte_data(lp->client, reg);
+	if (ret < 0) {
+		mutex_unlock(&lp->xfer_lock);
+		dev_err(lp->dev, "failed to read 0x%.2x\n", reg);
+		return ret;
+	}
+	mutex_unlock(&lp->xfer_lock);
+
+	*data = (u8)ret;
+	return 0;
+}
+
+static int lp855x_write_byte(struct lp855x *lp, u8 reg, u8 data)
+{
+	int ret;
+
+	mutex_lock(&lp->xfer_lock);
+	ret = i2c_smbus_write_byte_data(lp->client, reg, data);
+	mutex_unlock(&lp->xfer_lock);
+
+	return ret;
+}
+
+static bool lp855x_is_valid_rom_area(struct lp855x *lp, u8 addr)
+{
+	u8 start, end;
+
+	switch (lp->chip_id) {
+	case LP8550:
+	case LP8551:
+	case LP8552:
+	case LP8553:
+		start = EEPROM_START;
+		end = EEPROM_END;
+		break;
+	case LP8556:
+		start = EPROM_START;
+		end = EPROM_END;
+		break;
+	default:
+		return false;
+	}
+
+	return (addr >= start && addr <= end);
+}
+
+static int lp855x_init_registers(struct lp855x *lp)
+{
+	u8 val, addr;
+	int i, ret;
+	struct lp855x_platform_data *pd = lp->pdata;
+
+	val = pd->initial_brightness;
+	ret = lp855x_write_byte(lp, BRIGHTNESS_CTRL, val);
+	if (ret)
+		return ret;
+
+	val = pd->device_control;
+	ret = lp855x_write_byte(lp, DEVICE_CTRL, val);
+	if (ret)
+		return ret;
+
+	if (pd->load_new_rom_data && pd->size_program) {
+		for (i = 0; i < pd->size_program; i++) {
+			addr = pd->rom_data[i].addr;
+			val = pd->rom_data[i].val;
+			if (!lp855x_is_valid_rom_area(lp, addr))
+				continue;
+
+			ret = lp855x_write_byte(lp, addr, val);
+			if (ret)
+				return ret;
+		}
+	}
+
+	return ret;
+}
+
+static int lp855x_bl_update_status(struct backlight_device *bl)
+{
+	struct lp855x *lp = bl_get_data(bl);
+	enum lp855x_brightness_ctrl_mode mode = lp->pdata->mode;
+
+	if (bl->props.state & BL_CORE_SUSPENDED)
+		bl->props.brightness = 0;
+
+	if (mode == PWM_BASED) {
+		struct lp855x_pwm_data *pd = &lp->pdata->pwm_data;
+		int br = bl->props.brightness;
+		int max_br = bl->props.max_brightness;
+
+		if (pd->pwm_set_intensity)
+			pd->pwm_set_intensity(br, max_br);
+
+	} else if (mode == REGISTER_BASED) {
+		u8 val = bl->props.brightness;
+		lp855x_write_byte(lp, BRIGHTNESS_CTRL, val);
+	}
+
+	return 0;
+}
+
+static int lp855x_bl_get_brightness(struct backlight_device *bl)
+{
+	struct lp855x *lp = bl_get_data(bl);
+	enum lp855x_brightness_ctrl_mode mode = lp->pdata->mode;
+
+	if (mode == PWM_BASED) {
+		struct lp855x_pwm_data *pd = &lp->pdata->pwm_data;
+		int max_br = bl->props.max_brightness;
+
+		if (pd->pwm_get_intensity)
+			bl->props.brightness = pd->pwm_get_intensity(max_br);
+
+	} else if (mode == REGISTER_BASED) {
+		u8 val = 0;
+
+		lp855x_read_byte(lp, BRIGHTNESS_CTRL, &val);
+		bl->props.brightness = val;
+	}
+
+	return bl->props.brightness;
+}
+
+static const struct backlight_ops lp855x_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = lp855x_bl_update_status,
+	.get_brightness = lp855x_bl_get_brightness,
+};
+
+static int lp855x_backlight_register(struct lp855x *lp)
+{
+	struct backlight_device *bl;
+	struct backlight_properties props;
+	struct lp855x_platform_data *pdata = lp->pdata;
+	char *name = pdata->name ? : DEFAULT_BL_NAME;
+
+	props.type = BACKLIGHT_PLATFORM;
+	props.max_brightness = MAX_BRIGHTNESS;
+
+	if (pdata->initial_brightness > props.max_brightness)
+		pdata->initial_brightness = props.max_brightness;
+
+	props.brightness = pdata->initial_brightness;
+
+	bl = backlight_device_register(name, lp->dev, lp,
+				       &lp855x_bl_ops, &props);
+	if (IS_ERR(bl))
+		return PTR_ERR(bl);
+
+	lp->bl = bl;
+
+	return 0;
+}
+
+static void lp855x_backlight_unregister(struct lp855x *lp)
+{
+	if (lp->bl)
+		backlight_device_unregister(lp->bl);
+}
+
+static ssize_t lp855x_get_chip_id(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct lp855x *lp = dev_get_drvdata(dev);
+	return scnprintf(buf, BUF_SIZE, "%s\n", lp->chipname);
+}
+
+static ssize_t lp855x_get_bl_ctl_mode(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct lp855x *lp = dev_get_drvdata(dev);
+	enum lp855x_brightness_ctrl_mode mode = lp->pdata->mode;
+	char *strmode = NULL;
+
+	if (mode == PWM_BASED)
+		strmode = "pwm based";
+	else if (mode == REGISTER_BASED)
+		strmode = "register based";
+
+	return scnprintf(buf, BUF_SIZE, "%s\n", strmode);
+}
+
+static DEVICE_ATTR(chip_id, S_IRUGO, lp855x_get_chip_id, NULL);
+static DEVICE_ATTR(bl_ctl_mode, S_IRUGO, lp855x_get_bl_ctl_mode, NULL);
+
+static struct attribute *lp855x_attributes[] = {
+	&dev_attr_chip_id.attr,
+	&dev_attr_bl_ctl_mode.attr,
+	NULL,
+};
+
+static const struct attribute_group lp855x_attr_group = {
+	.attrs = lp855x_attributes,
+};
+
+static int lp855x_probe(struct i2c_client *cl, const struct i2c_device_id *id)
+{
+	struct lp855x *lp;
+	struct lp855x_platform_data *pdata = cl->dev.platform_data;
+	enum lp855x_brightness_ctrl_mode mode;
+	int ret;
+
+	if (!pdata) {
+		dev_err(&cl->dev, "no platform data supplied\n");
+		return -EINVAL;
+	}
+
+	if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_I2C_BLOCK))
+		return -EIO;
+
+	lp = devm_kzalloc(&cl->dev, sizeof(struct lp855x), GFP_KERNEL);
+	if (!lp)
+		return -ENOMEM;
+
+	mode = pdata->mode;
+	lp->client = cl;
+	lp->dev = &cl->dev;
+	lp->pdata = pdata;
+	lp->chipname = id->name;
+	lp->chip_id = id->driver_data;
+	i2c_set_clientdata(cl, lp);
+
+	mutex_init(&lp->xfer_lock);
+
+	ret = lp855x_init_registers(lp);
+	if (ret) {
+		dev_err(lp->dev, "i2c communication err: %d", ret);
+		if (mode == REGISTER_BASED)
+			goto err_dev;
+	}
+
+	ret = lp855x_backlight_register(lp);
+	if (ret) {
+		dev_err(lp->dev,
+			"failed to register backlight. err: %d\n", ret);
+		goto err_dev;
+	}
+
+	ret = sysfs_create_group(&lp->dev->kobj, &lp855x_attr_group);
+	if (ret) {
+		dev_err(lp->dev, "failed to register sysfs. err: %d\n", ret);
+		goto err_sysfs;
+	}
+
+	backlight_update_status(lp->bl);
+	return 0;
+
+err_sysfs:
+	lp855x_backlight_unregister(lp);
+err_dev:
+	return ret;
+}
+
+static int __devexit lp855x_remove(struct i2c_client *cl)
+{
+	struct lp855x *lp = i2c_get_clientdata(cl);
+
+	lp->bl->props.brightness = 0;
+	backlight_update_status(lp->bl);
+	sysfs_remove_group(&lp->dev->kobj, &lp855x_attr_group);
+	lp855x_backlight_unregister(lp);
+
+	return 0;
+}
+
+static const struct i2c_device_id lp855x_ids[] = {
+	{"lp8550", LP8550},
+	{"lp8551", LP8551},
+	{"lp8552", LP8552},
+	{"lp8553", LP8553},
+	{"lp8556", LP8556},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, lp855x_ids);
+
+static struct i2c_driver lp855x_driver = {
+	.driver = {
+		   .name = "lp855x",
+		   },
+	.probe = lp855x_probe,
+	.remove = __devexit_p(lp855x_remove),
+	.id_table = lp855x_ids,
+};
+
+module_i2c_driver(lp855x_driver);
+
+MODULE_DESCRIPTION("Texas Instruments LP855x Backlight driver");
+MODULE_AUTHOR("Milo Kim <[e-mail]>");
+MODULE_LICENSE("GPL");

include/linux/lp855x.h

···
+/*
+ * LP855x Backlight Driver
+ *
+ *			Copyright (C) 2011 Texas Instruments
+ *
+ * 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.
+ *
+ */
+
+#ifndef _LP855X_H
+#define _LP855X_H
+
+#define BL_CTL_SHFT	(0)
+#define BRT_MODE_SHFT	(1)
+#define BRT_MODE_MASK	(0x06)
+
+/* Enable backlight. Only valid when BRT_MODE=10(I2C only) */
+#define ENABLE_BL	(1)
+#define DISABLE_BL	(0)
+
+#define I2C_CONFIG(id)	id ## _I2C_CONFIG
+#define PWM_CONFIG(id)	id ## _PWM_CONFIG
+
+/* DEVICE CONTROL register - LP8550 */
+#define LP8550_PWM_CONFIG	(LP8550_PWM_ONLY << BRT_MODE_SHFT)
+#define LP8550_I2C_CONFIG	((ENABLE_BL << BL_CTL_SHFT) | \
+				(LP8550_I2C_ONLY << BRT_MODE_SHFT))
+
+/* DEVICE CONTROL register - LP8551 */
+#define LP8551_PWM_CONFIG	LP8550_PWM_CONFIG
+#define LP8551_I2C_CONFIG	LP8550_I2C_CONFIG
+
+/* DEVICE CONTROL register - LP8552 */
+#define LP8552_PWM_CONFIG	LP8550_PWM_CONFIG
+#define LP8552_I2C_CONFIG	LP8550_I2C_CONFIG
+
+/* DEVICE CONTROL register - LP8553 */
+#define LP8553_PWM_CONFIG	LP8550_PWM_CONFIG
+#define LP8553_I2C_CONFIG	LP8550_I2C_CONFIG
+
+/* DEVICE CONTROL register - LP8556 */
+#define LP8556_PWM_CONFIG	(LP8556_PWM_ONLY << BRT_MODE_SHFT)
+#define LP8556_COMB1_CONFIG	(LP8556_COMBINED1 << BRT_MODE_SHFT)
+#define LP8556_I2C_CONFIG	((ENABLE_BL << BL_CTL_SHFT) | \
+				(LP8556_I2C_ONLY << BRT_MODE_SHFT))
+#define LP8556_COMB2_CONFIG	(LP8556_COMBINED2 << BRT_MODE_SHFT)
+
+/* ROM area boundary */
+#define EEPROM_START	(0xA0)
+#define EEPROM_END	(0xA7)
+#define EPROM_START	(0xA0)
+#define EPROM_END	(0xAF)
+
+enum lp855x_chip_id {
+	LP8550,
+	LP8551,
+	LP8552,
+	LP8553,
+	LP8556,
+};
+
+enum lp855x_brightness_ctrl_mode {
+	PWM_BASED = 1,
+	REGISTER_BASED,
+};
+
+enum lp8550_brighntess_source {
+	LP8550_PWM_ONLY,
+	LP8550_I2C_ONLY = 2,
+};
+
+enum lp8551_brighntess_source {
+	LP8551_PWM_ONLY = LP8550_PWM_ONLY,
+	LP8551_I2C_ONLY = LP8550_I2C_ONLY,
+};
+
+enum lp8552_brighntess_source {
+	LP8552_PWM_ONLY = LP8550_PWM_ONLY,
+	LP8552_I2C_ONLY = LP8550_I2C_ONLY,
+};
+
+enum lp8553_brighntess_source {
+	LP8553_PWM_ONLY = LP8550_PWM_ONLY,
+	LP8553_I2C_ONLY = LP8550_I2C_ONLY,
+};
+
+enum lp8556_brightness_source {
+	LP8556_PWM_ONLY,
+	LP8556_COMBINED1,	/* pwm + i2c before the shaper block */
+	LP8556_I2C_ONLY,
+	LP8556_COMBINED2,	/* pwm + i2c after the shaper block */
+};
+
+struct lp855x_pwm_data {
+	void (*pwm_set_intensity) (int brightness, int max_brightness);
+	int (*pwm_get_intensity) (int max_brightness);
+};
+
+struct lp855x_rom_data {
+	u8 addr;
+	u8 val;
+};
+
+/**
+ * struct lp855x_platform_data
+ * @name : Backlight driver name. If it is not defined, default name is set.
+ * @mode : brightness control by pwm or lp855x register
+ * @device_control : value of DEVICE CONTROL register
+ * @initial_brightness : initial value of backlight brightness
+ * @pwm_data : platform specific pwm generation functions.
+		Only valid when mode is PWM_BASED.
+ * @load_new_rom_data :
+	0 : use default configuration data
+	1 : update values of eeprom or eprom registers on loading driver
+ * @size_program : total size of lp855x_rom_data
+ * @rom_data : list of new eeprom/eprom registers
+ */
+struct lp855x_platform_data {
+	char *name;
+	enum lp855x_brightness_ctrl_mode mode;
+	u8 device_control;
+	int initial_brightness;
+	struct lp855x_pwm_data pwm_data;
+	u8 load_new_rom_data;
+	int size_program;
+	struct lp855x_rom_data *rom_data;
+};
+
+#endif