[PATCH v5 1/2] backlight arcxcnn add support for ArcticSand devices

[Olimpiu Dejeu <olimpiu@arcticsand.com>]

backlight: Add support for Arctic Sand LED backlight driver chips
This driver provides support for the Arctic Sand arc2c0608 chip, 
    and provides a framework to support future devices.
Signed-off-by: Olimpiu Dejeu <olimpiu@arcticsand.com>
---
v4 => v5:
- Code style changes per Joe Perches and Jingoo Han
v3 => v4:
- Code style changes per Joe Perches and Jingoo Han
v2 => v3:
- Renamed variables to comply with conventions on naming
- Corrected device name in arcxcnn.h
v1 => v2:
- Removed "magic numbers" to initialize registers
- Cleaned up device tree bindings
- Fixed code style to address comments and pass "checkpatch"
- Removed unneeded debug and testing code

 drivers/video/backlight/Kconfig      |   7 +
 drivers/video/backlight/Makefile     |   1 +
 drivers/video/backlight/arcxcnn_bl.c | 451 +++++++++++++++++++++++++++++++++++
 include/linux/i2c/arcxcnn.h          |  51 ++++
 4 files changed, 510 insertions(+)
 create mode 100644 drivers/video/backlight/arcxcnn_bl.c
 create mode 100644 include/linux/i2c/arcxcnn.h

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 5ffa4b4..4e1d2ad 100644
--- a/drivers/video/backlight/Kconfig
+++ b/drivers/video/backlight/Kconfig
@@ -460,6 +460,13 @@ config BACKLIGHT_BD6107
 	help
 	  If you have a Rohm BD6107 say Y to enable the backlight driver.
 
+config BACKLIGHT_ARCXCNN
+	tristate "Backlight driver for the Arctic Sands ARCxCnnnn family"
+	depends on I2C
+	help
+	  If you have an ARCxCnnnn family backlight say Y to enable
+	  the backlight driver.
+
 endif # BACKLIGHT_CLASS_DEVICE
 
 endif # BACKLIGHT_LCD_SUPPORT
diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
index 16ec534..8905129 100644
--- a/drivers/video/backlight/Makefile
+++ b/drivers/video/backlight/Makefile
@@ -55,3 +55,4 @@ obj-$(CONFIG_BACKLIGHT_SKY81452)	+= sky81452-backlight.o
 obj-$(CONFIG_BACKLIGHT_TOSA)		+= tosa_bl.o
 obj-$(CONFIG_BACKLIGHT_TPS65217)	+= tps65217_bl.o
 obj-$(CONFIG_BACKLIGHT_WM831X)		+= wm831x_bl.o
+obj-$(CONFIG_BACKLIGHT_ARCXCNN) 	+= arcxcnn_bl.o
diff --git a/drivers/video/backlight/arcxcnn_bl.c b/drivers/video/backlight/arcxcnn_bl.c
new file mode 100644
index 0000000..284df08
--- /dev/null
+++ b/drivers/video/backlight/arcxcnn_bl.c
@@ -0,0 +1,451 @@
+/*
+ * Backlight driver for ArcticSand ARC_X_C_0N_0N Devices
+ *
+ * Copyright 2016 ArcticSand, Inc.
+ * Author : Brian Dodge <bdodge@arcticsand.com>
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#include "linux/i2c/arcxcnn.h"
+
+#define ARCXCNN_CMD		0x00	/* Command Register */
+#define ARCXCNN_CMD_STDBY	0x80	/*   I2C Standby */
+#define ARCXCNN_CMD_RESET	0x40	/*   Reset */
+#define ARCXCNN_CMD_BOOST	0x10	/*   Boost */
+#define ARCXCNN_CMD_OVP_MASK	0x0C	/*   --- Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_XXV	0x0C	/*   <rsvrd> Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_20V	0x08	/*   20v Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_24V	0x04	/*   24v Over Voltage Threshold */
+#define ARCXCNN_CMD_OVP_31V	0x00	/*   31.4v Over Voltage Threshold */
+#define ARCXCNN_CMD_EXT_COMP	0x01	/*   part (0) or full (1) ext. comp */
+
+#define ARCXCNN_CONFIG		0x01	/* Configuration */
+#define ARCXCNN_STATUS1		0x02	/* Status 1 */
+#define ARCXCNN_STATUS2		0x03	/* Status 2 */
+#define ARCXCNN_FADECTRL	0x04	/* Fading Control */
+#define ARCXCNN_ILED_CONFIG	0x05	/* ILED Configuration */
+#define ARCXCNN_ILED_DIM_PWM	0x00	/*   config dim mode pwm */
+#define ARCXCNN_ILED_DIM_INT	0x04	/*   config dim mode internal */
+#define ARCXCNN_LEDEN		0x06	/* LED Enable Register */
+#define ARCXCNN_LEDEN_ISETEXT	0x80	/*   Full-scale current set extern */
+#define ARCXCNN_LEDEN_MASK	0x3F	/*   LED string enables mask */
+#define ARCXCNN_LEDEN_BITS	0x06	/*   Bits of LED string enables */
+#define ARCXCNN_LEDEN_LED1	0x01
+#define ARCXCNN_LEDEN_LED2	0x02
+#define ARCXCNN_LEDEN_LED3	0x04
+#define ARCXCNN_LEDEN_LED4	0x08
+#define ARCXCNN_LEDEN_LED5	0x10
+#define ARCXCNN_LEDEN_LED6	0x20
+
+#define ARCXCNN_WLED_ISET_LSB	0x07	/* LED ISET LSB (in upper nibble) */
+#define ARCXCNN_WLED_ISET_LSB_SHIFT 0x04  /* ISET LSB Left Shift */
+#define ARCXCNN_WLED_ISET_MSB	0x08	/* LED ISET MSB (8 bits) */
+
+#define ARCXCNN_DIMFREQ		0x09
+#define ARCXCNN_COMP_CONFIG	0x0A
+#define ARCXCNN_FILT_CONFIG	0x0B
+#define ARCXCNN_IMAXTUNE	0x0C
+#define ARCXCNN_ID_MSB		0x1E
+#define ARCXCNN_ID_LSB		0x1F
+
+#define MAX_BRIGHTNESS		4095
+
+static int no_reset_on_remove;
+module_param_named(noreset, no_reset_on_remove, int, 0644);
+MODULE_PARM_DESC(noreset, "No reset on module removal");
+
+static int ibright = 60;
+module_param_named(ibright, ibright, int, 0644);
+MODULE_PARM_DESC(ibright, "Initial brightness (when no plat data)");
+
+static int ileden = ARCXCNN_LEDEN_MASK;
+module_param_named(ileden, ileden, int, 0644);
+MODULE_PARM_DESC(ileden, "Initial LED String Enables (when no plat data)");
+
+struct arcxcnn {
+	char chipname[64];
+	struct i2c_client *client;
+	struct backlight_device *bl;
+	struct device *dev;
+	struct arcxcnn_platform_data *pdata;
+};
+
+static int arcxcnn_update_bit(struct arcxcnn *lp, u8 reg, u8 mask, u8 data)
+{
+	int ret;
+	u8 tmp;
+
+	ret = i2c_smbus_read_byte_data(lp->client, reg);
+	if (ret < 0) {
+		dev_err(lp->dev, "failed to read 0x%.2x\n", reg);
+		return ret;
+	}
+
+	tmp = (u8)ret;
+	tmp &= ~mask;
+	tmp |= data & mask;
+
+	return i2c_smbus_write_byte_data(lp->client, reg, tmp);
+}
+
+static int arcxcnn_set_brightness(struct arcxcnn *lp, u32 brightness)
+{
+	int ret;
+	u8 val;
+
+	/* lower nibble of brightness goes in upper nibble of LSB register */
+	val = (brightness & 0xF) << ARCXCNN_WLED_ISET_LSB_SHIFT;
+	ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_WLED_ISET_LSB, val);
+	if (ret < 0)
+		return ret;
+
+	/* remaining 8 bits of brightness go in MSB register */
+	val = (brightness >> 4);
+	ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_WLED_ISET_MSB, val);
+
+	return ret;
+}
+
+static int arcxcnn_bl_update_status(struct backlight_device *bl)
+{
+	struct arcxcnn *lp = bl_get_data(bl);
+	u32 brightness = bl->props.brightness;
+
+	if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+		brightness = 0;
+
+	arcxcnn_set_brightness(lp, brightness);
+
+	/* set power-on/off/save modes */
+	arcxcnn_update_bit(lp, ARCXCNN_CMD, ARCXCNN_CMD_STDBY,
+		(bl->props.power == 0) ? 0 : ARCXCNN_CMD_STDBY);
+
+	return 0;
+}
+
+static const struct backlight_ops arcxcnn_bl_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = arcxcnn_bl_update_status,
+};
+
+static int arcxcnn_backlight_register(struct arcxcnn *lp)
+{
+	struct backlight_properties *props;
+	const char *name = lp->pdata->name ? : "arctic_bl";
+
+	props = devm_kzalloc(lp->dev, sizeof(*props), GFP_KERNEL);
+	if (!props)
+		return -ENOMEM;
+
+	props->type = BACKLIGHT_PLATFORM;
+	props->max_brightness = MAX_BRIGHTNESS;
+
+	if (lp->pdata->initial_brightness > props->max_brightness)
+		lp->pdata->initial_brightness = props->max_brightness;
+
+	props->brightness = lp->pdata->initial_brightness;
+
+	lp->bl = devm_backlight_device_register(lp->dev, name, lp->dev, lp,
+				       &arcxcnn_bl_ops, props);
+	if (IS_ERR(lp->bl))
+		return PTR_ERR(lp->bl);
+
+	return 0;
+}
+
+static ssize_t arcxcnn_chip_id_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct arcxcnn *lp = dev_get_drvdata(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", lp->chipname);
+}
+
+static ssize_t arcxcnn_leden_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct arcxcnn *lp = dev_get_drvdata(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%02X\n", lp->pdata->leden);
+}
+
+static ssize_t arcxcnn_leden_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct arcxcnn *lp = dev_get_drvdata(dev);
+	unsigned long leden;
+
+	if (kstrtoul(buf, 0, &leden))
+		return 0;
+
+	if (leden != lp->pdata->leden) {
+		/* don't allow 0 for leden, use power to turn all off */
+		if (leden == 0)
+			return -EINVAL;
+		lp->pdata->leden = leden & ARCXCNN_LEDEN_MASK;
+		arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
+			ARCXCNN_LEDEN_MASK, lp->pdata->leden);
+	}
+
+	return len;
+}
+
+static DEVICE_ATTR(chip_id, 0444, arcxcnn_chip_id_show, NULL);
+static DEVICE_ATTR(leden, 0664, arcxcnn_leden_show, arcxcnn_leden_store);
+
+static struct attribute *arcxcnn_attributes[] = {
+	&dev_attr_chip_id.attr,
+	&dev_attr_leden.attr,
+	NULL,
+};
+
+static const struct attribute_group arcxcnn_attr_group = {
+	.attrs = arcxcnn_attributes,
+};
+
+static void arcxcnn_parse_dt(struct arcxcnn *lp)
+{
+	struct device *dev = lp->dev;
+	struct device_node *node = dev->of_node;
+	u32 prog_val, num_entry, entry, sources[ARCXCNN_LEDEN_BITS];
+	int ret;
+
+	/* device tree entry isn't required, defaults are OK */
+	if (!node)
+		return;
+
+	ret = of_property_read_string(node, "label", &lp->pdata->name);
+	if (ret < 0)
+		lp->pdata->name = NULL;
+
+	ret = of_property_read_u32(node, "default-brightness", &prog_val);
+	if (ret == 0)
+		lp->pdata->initial_brightness = prog_val;
+
+	ret = of_property_read_u32(node, "arc,led-config-0", &prog_val);
+	if (ret == 0)
+		lp->pdata->led_config_0 = (u8)prog_val;
+
+	ret = of_property_read_u32(node, "arc,led-config-1", &prog_val);
+	if (ret == 0)
+		lp->pdata->led_config_1 = (u8)prog_val;
+
+	ret = of_property_read_u32(node, "arc,dim-freq", &prog_val);
+	if (ret == 0)
+		lp->pdata->dim_freq = (u8)prog_val;
+
+	ret = of_property_read_u32(node, "arc,comp-config", &prog_val);
+	if (ret == 0)
+		lp->pdata->comp_config = (u8)prog_val;
+
+	ret = of_property_read_u32(node, "arc,filter-config", &prog_val);
+	if (ret == 0)
+		lp->pdata->filter_config = (u8)prog_val;
+
+	ret = of_property_read_u32(node, "arc,trim-config", &prog_val);
+	if (ret == 0)
+		lp->pdata->trim_config = (u8)prog_val;
+
+	ret = of_property_count_u32_elems(node, "led-sources");
+	if (ret < 0) {
+		lp->pdata->leden = ARCXCNN_LEDEN_MASK; /* all on is default */
+	} else {
+		num_entry = ret;
+		if (num_entry > ARCXCNN_LEDEN_BITS)
+			num_entry = ARCXCNN_LEDEN_BITS;
+
+		ret = of_property_read_u32_array(node, "led-sources", sources,
+					num_entry);
+		if (ret < 0) {
+			dev_err(dev, "led-sources node is invalid.\n");
+			return;
+		}
+
+		lp->pdata->leden = 0;
+
+		/* for each enable in source, set bit in led enable */
+		for (entry = 0; entry < num_entry; entry++) {
+			u8 onbit = 1 << sources[entry];
+			lp->pdata->leden |= onbit;
+		}
+	}
+}
+
+static int arcxcnn_probe(struct i2c_client *cl, const struct i2c_device_id *id)
+{
+	struct arcxcnn *lp;
+	int ret;
+	u8 regval;
+	u16 chipid;
+
+	if (!i2c_check_functionality(cl->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -EIO;
+
+	lp = devm_kzalloc(&cl->dev, sizeof(*lp), GFP_KERNEL);
+	if (!lp)
+		return -ENOMEM;
+
+	lp->client = cl;
+	lp->dev = &cl->dev;
+	lp->pdata = dev_get_platdata(&cl->dev);
+
+	/* reset the device */
+	i2c_smbus_write_byte_data(lp->client,
+		ARCXCNN_CMD, ARCXCNN_CMD_RESET);
+
+	/* read device ID */
+	regval = i2c_smbus_read_byte_data(lp->client, ARCXCNN_ID_MSB);
+	chipid = regval;
+	chipid <<= 8;
+
+	regval = i2c_smbus_read_byte_data(lp->client, ARCXCNN_ID_LSB);
+	chipid |= regval;
+
+	snprintf(lp->chipname, sizeof(lp->chipname),
+		"%s-%04X", id->name, chipid);
+
+	if (!lp->pdata) {
+		lp->pdata = devm_kzalloc(lp->dev,
+				sizeof(*lp->pdata), GFP_KERNEL);
+		if (!lp->pdata)
+			return -ENOMEM;
+
+		/* Setup defaults based on power-on defaults */
+		lp->pdata->name = NULL;
+		lp->pdata->initial_brightness = ibright;
+		lp->pdata->leden = ileden;
+
+		lp->pdata->led_config_0 = i2c_smbus_read_byte_data(
+			lp->client, ARCXCNN_FADECTRL);
+
+		lp->pdata->led_config_1 = i2c_smbus_read_byte_data(
+			lp->client, ARCXCNN_ILED_CONFIG);
+		/* insure dim mode is not default pwm */
+		lp->pdata->led_config_1 |= ARCXCNN_ILED_DIM_INT;
+
+		lp->pdata->dim_freq = i2c_smbus_read_byte_data(
+			lp->client, ARCXCNN_DIMFREQ);
+
+		lp->pdata->comp_config = i2c_smbus_read_byte_data(
+			lp->client, ARCXCNN_COMP_CONFIG);
+
+		lp->pdata->filter_config = i2c_smbus_read_byte_data(
+			lp->client, ARCXCNN_FILT_CONFIG);
+
+		lp->pdata->trim_config = i2c_smbus_read_byte_data(
+			lp->client, ARCXCNN_IMAXTUNE);
+
+		if (IS_ENABLED(CONFIG_OF))
+			arcxcnn_parse_dt(lp);
+	}
+
+	i2c_set_clientdata(cl, lp);
+
+	/* constrain settings to what is possible */
+	if (lp->pdata->initial_brightness > MAX_BRIGHTNESS)
+		lp->pdata->initial_brightness = MAX_BRIGHTNESS;
+
+	/* set initial brightness */
+	arcxcnn_set_brightness(lp, lp->pdata->initial_brightness);
+
+	/* set other register values directly */
+	i2c_smbus_write_byte_data(lp->client, ARCXCNN_FADECTRL,
+		lp->pdata->led_config_0);
+	i2c_smbus_write_byte_data(lp->client, ARCXCNN_ILED_CONFIG,
+		lp->pdata->led_config_1);
+	i2c_smbus_write_byte_data(lp->client, ARCXCNN_DIMFREQ,
+		lp->pdata->dim_freq);
+	i2c_smbus_write_byte_data(lp->client, ARCXCNN_COMP_CONFIG,
+		lp->pdata->comp_config);
+	i2c_smbus_write_byte_data(lp->client, ARCXCNN_FILT_CONFIG,
+		lp->pdata->filter_config);
+	i2c_smbus_write_byte_data(lp->client, ARCXCNN_IMAXTUNE,
+		lp->pdata->trim_config);
+
+	/* set initial LED Enables */
+	arcxcnn_update_bit(lp, ARCXCNN_LEDEN,
+		ARCXCNN_LEDEN_MASK, lp->pdata->leden);
+
+	ret = arcxcnn_backlight_register(lp);
+	if (ret) {
+		dev_err(lp->dev,
+			"failed to register backlight. err: %d\n", ret);
+		return ret;
+	}
+
+	ret = sysfs_create_group(&lp->dev->kobj, &arcxcnn_attr_group);
+	if (ret) {
+		dev_err(lp->dev, "failed to register sysfs. err: %d\n", ret);
+		return ret;
+	}
+
+	backlight_update_status(lp->bl);
+
+	return 0;
+}
+
+static int arcxcnn_remove(struct i2c_client *cl)
+{
+	struct arcxcnn *lp = i2c_get_clientdata(cl);
+
+	if (!no_reset_on_remove) {
+		/* disable all strings */
+		i2c_smbus_write_byte_data(lp->client,
+			ARCXCNN_LEDEN, 0x00);
+		/* reset the device */
+		i2c_smbus_write_byte_data(lp->client,
+			ARCXCNN_CMD, ARCXCNN_CMD_RESET);
+	}
+	lp->bl->props.brightness = 0;
+
+	backlight_update_status(lp->bl);
+
+	sysfs_remove_group(&lp->dev->kobj, &arcxcnn_attr_group);
+
+	return 0;
+}
+
+static const struct of_device_id arcxcnn_dt_ids[] = {
+	{ .compatible = "arc,arc2c0608" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, arcxcnn_dt_ids);
+
+static const struct i2c_device_id arcxcnn_ids[] = {
+	{"arc2c0608", ARC2C0608},
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, arcxcnn_ids);
+
+static struct i2c_driver arcxcnn_driver = {
+	.driver = {
+		.name = "arcxcnn_bl",
+		.of_match_table = of_match_ptr(arcxcnn_dt_ids),
+	},
+	.probe = arcxcnn_probe,
+	.remove = arcxcnn_remove,
+	.id_table = arcxcnn_ids,
+};
+module_i2c_driver(arcxcnn_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Brian Dodge <bdodge@arcticsand.com>");
+MODULE_DESCRIPTION("ARCXCNN Backlight driver");
diff --git a/include/linux/i2c/arcxcnn.h b/include/linux/i2c/arcxcnn.h
new file mode 100644
index 0000000..e378d63
--- /dev/null
+++ b/include/linux/i2c/arcxcnn.h
@@ -0,0 +1,51 @@
+/*
+ * Backlight driver for ArcticSand ARCXCNN Devices
+ *
+ * Copyright 2016 ArcticSand, Inc.
+ * Author : Brian Dodge <bdodge@arcticsand.com>
+ *
+ * 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.
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _ARCXCNN_H
+#define _ARCXCNN_H
+
+enum arcxcnn_chip_id {
+	ARC2C0608
+};
+
+/**
+ * struct arcxcnn_platform_data
+ * @name		: Backlight driver name (NULL will use default)
+ * @initial_brightness	: initial value of backlight brightness
+ * @leden		: initial LED string enables, upper bit is global on/off
+ * @led_config_0	: fading speed (period between intensity steps)
+ * @led_config_1	: misc settings, see datasheet
+ * @dim_freq		: pwm dimming frequency if in pwm mode
+ * @comp_config		: misc config, see datasheet
+ * @filter_config	: RC/PWM filter config, see datasheet
+ * @trim_config		: full scale current trim, see datasheet
+ */
+struct arcxcnn_platform_data {
+	const char *name;
+	u16 initial_brightness;
+	u8	leden;
+	u8	led_config_0;
+	u8	led_config_1;
+	u8	dim_freq;
+	u8	comp_config;
+	u8	filter_config;
+	u8	trim_config;
+};
+
+#endif
-- 
2.7.4