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>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

3 files changed, 427 insertions, 0 deletions

diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
index 5ffa4b4e26c0..4e1d2ad50ba1 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 16ec534cff30..8905129691e8 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 000000000000..dec790de72ff
--- /dev/null
+++ b/drivers/video/backlight/arcxcnn_bl.c
@@ -0,0 +1,419 @@
+/*
+ * 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>
+
+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;
+};
+
+#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
+#define INIT_BRIGHT             60
+
+struct arcxcnn {
+        struct i2c_client *client;
+        struct backlight_device *bl;
+        struct device *dev;
+        struct arcxcnn_platform_data *pdata;
+};
+
+static int arcxcnn_update_field(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);
+        return i2c_smbus_write_byte_data(lp->client,
+                ARCXCNN_WLED_ISET_MSB, val);
+}
+
+static int arcxcnn_bl_update_status(struct backlight_device *bl)
+{
+        struct arcxcnn *lp = bl_get_data(bl);
+        u32 brightness = bl->props.brightness;
+        int ret;
+
+        if (bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK))
+                brightness = 0;
+
+        ret = arcxcnn_set_brightness(lp, brightness);
+        if (ret)
+                return ret;
+
+        /* set power-on/off/save modes */
+        return arcxcnn_update_field(lp, ARCXCNN_CMD, ARCXCNN_CMD_STDBY,
+                (bl->props.power == 0) ? 0 : ARCXCNN_CMD_STDBY);
+}
+
+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);
+        return PTR_ERR_OR_ZERO(lp->bl);
+}
+
+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;
+
+        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 */
+        ret = i2c_smbus_write_byte_data(lp->client,
+                ARCXCNN_CMD, ARCXCNN_CMD_RESET);
+        if (ret)
+                goto probe_err;
+
+        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 = INIT_BRIGHT;
+                lp->pdata->leden = ARCXCNN_LEDEN_MASK;
+
+                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 */
+        ret = arcxcnn_set_brightness(lp, lp->pdata->initial_brightness);
+        if (ret)
+                goto probe_err;
+
+        /* set other register values directly */
+        ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_FADECTRL,
+                lp->pdata->led_config_0);
+        if (ret)
+                goto probe_err;
+
+        ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_ILED_CONFIG,
+                lp->pdata->led_config_1);
+        if (ret)
+                goto probe_err;
+
+        ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_DIMFREQ,
+                lp->pdata->dim_freq);
+        if (ret)
+                goto probe_err;
+
+        ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_COMP_CONFIG,
+                lp->pdata->comp_config);
+        if (ret)
+                goto probe_err;
+
+        ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_FILT_CONFIG,
+                lp->pdata->filter_config);
+        if (ret)
+                goto probe_err;
+
+        ret = i2c_smbus_write_byte_data(lp->client, ARCXCNN_IMAXTUNE,
+                lp->pdata->trim_config);
+        if (ret)
+                goto probe_err;
+
+        /* set initial LED Enables */
+        arcxcnn_update_field(lp, ARCXCNN_LEDEN,
+                ARCXCNN_LEDEN_MASK, lp->pdata->leden);
+
+        ret = arcxcnn_backlight_register(lp);
+        if (ret)
+                goto probe_register_err;
+
+        backlight_update_status(lp->bl);
+
+        return 0;
+
+probe_register_err:
+        dev_err(lp->dev,
+                "failed to register backlight.\n");
+
+probe_err:
+        dev_err(lp->dev,
+                "failure ret: %d\n", ret);
+        return ret;
+}
+
+static int arcxcnn_remove(struct i2c_client *cl)
+{
+        struct arcxcnn *lp = i2c_get_clientdata(cl);
+
+        /* disable all strings (ignore errors) */
+        i2c_smbus_write_byte_data(lp->client,
+                ARCXCNN_LEDEN, 0x00);
+        /* reset the device (ignore errors) */
+        i2c_smbus_write_byte_data(lp->client,
+                ARCXCNN_CMD, ARCXCNN_CMD_RESET);
+
+        lp->bl->props.brightness = 0;
+
+        backlight_update_status(lp->bl);
+
+        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");