lp8788_bl.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * TI LP8788 MFD - backlight driver
  4 *
  5 * Copyright 2012 Texas Instruments
  6 *
  7 * Author: Milo(Woogyom) Kim <milo.kim@ti.com>
  8 */
  9
 10#include <linux/backlight.h>
 11#include <linux/err.h>
 12#include <linux/mfd/lp8788.h>
 13#include <linux/module.h>
 14#include <linux/platform_device.h>
 15#include <linux/slab.h>
 16
 17/* Register address */
 18#define LP8788_BL_CONFIG		0x96
 19#define LP8788_BL_EN			BIT(0)
 20#define LP8788_BL_PWM_INPUT_EN		BIT(5)
 21#define LP8788_BL_FULLSCALE_SHIFT	2
 22#define LP8788_BL_DIM_MODE_SHIFT	1
 23#define LP8788_BL_PWM_POLARITY_SHIFT	6
 24
 25#define LP8788_BL_BRIGHTNESS		0x97
 26
 27#define LP8788_BL_RAMP			0x98
 28#define LP8788_BL_RAMP_RISE_SHIFT	4
 29
 30#define MAX_BRIGHTNESS			127
 31#define DEFAULT_BL_NAME			"lcd-backlight"
 32
 33struct lp8788_bl {
 34	struct lp8788 *lp;
 35	struct backlight_device *bl_dev;
 36};
 37
 38static int lp8788_backlight_configure(struct lp8788_bl *bl)
 39{
 40	int ret;
 41	u8 val;
 42
 43	/* Brightness ramp up/down */
 44	val = (LP8788_RAMP_8192us << LP8788_BL_RAMP_RISE_SHIFT) | LP8788_RAMP_8192us;
 45	ret = lp8788_write_byte(bl->lp, LP8788_BL_RAMP, val);
 46	if (ret)
 47		return ret;
 48
 49	/* Fullscale current setting */
 50	val = (LP8788_FULLSCALE_1900uA << LP8788_BL_FULLSCALE_SHIFT) |
 51		(LP8788_DIM_EXPONENTIAL << LP8788_BL_DIM_MODE_SHIFT);
 52
 53	/* Brightness control mode */
 54	val |= LP8788_BL_EN;
 55
 56	return lp8788_write_byte(bl->lp, LP8788_BL_CONFIG, val);
 57}
 58
 59static int lp8788_bl_update_status(struct backlight_device *bl_dev)
 60{
 61	struct lp8788_bl *bl = bl_get_data(bl_dev);
 62
 63	if (bl_dev->props.state & BL_CORE_SUSPENDED)
 64		bl_dev->props.brightness = 0;
 65
 66	lp8788_write_byte(bl->lp, LP8788_BL_BRIGHTNESS, bl_dev->props.brightness);
 67
 68	return 0;
 69}
 70
 71static const struct backlight_ops lp8788_bl_ops = {
 72	.options = BL_CORE_SUSPENDRESUME,
 73	.update_status = lp8788_bl_update_status,
 74};
 75
 76static int lp8788_backlight_register(struct lp8788_bl *bl)
 77{
 78	struct backlight_device *bl_dev;
 79	struct backlight_properties props;
 80
 81	memset(&props, 0, sizeof(struct backlight_properties));
 82	props.type = BACKLIGHT_PLATFORM;
 83	props.max_brightness = MAX_BRIGHTNESS;
 84
 85	/* Initial brightness */
 86	props.brightness = 0;
 87
 88	/* Backlight device name */
 89	bl_dev = backlight_device_register(DEFAULT_BL_NAME, bl->lp->dev, bl,
 90				       &lp8788_bl_ops, &props);
 91	if (IS_ERR(bl_dev))
 92		return PTR_ERR(bl_dev);
 93
 94	bl->bl_dev = bl_dev;
 95
 96	return 0;
 97}
 98
 99static void lp8788_backlight_unregister(struct lp8788_bl *bl)
100{
101	struct backlight_device *bl_dev = bl->bl_dev;
102
103	backlight_device_unregister(bl_dev);
104}
105
106static ssize_t lp8788_get_bl_ctl_mode(struct device *dev,
107				     struct device_attribute *attr, char *buf)
108{
109	const char *strmode = "Register based";
110
111	return scnprintf(buf, PAGE_SIZE, "%s\n", strmode);
112}
113
114static DEVICE_ATTR(bl_ctl_mode, S_IRUGO, lp8788_get_bl_ctl_mode, NULL);
115
116static struct attribute *lp8788_attributes[] = {
117	&dev_attr_bl_ctl_mode.attr,
118	NULL,
119};
120
121static const struct attribute_group lp8788_attr_group = {
122	.attrs = lp8788_attributes,
123};
124
125static int lp8788_backlight_probe(struct platform_device *pdev)
126{
127	struct lp8788 *lp = dev_get_drvdata(pdev->dev.parent);
128	struct lp8788_bl *bl;
129	int ret;
130
131	bl = devm_kzalloc(lp->dev, sizeof(struct lp8788_bl), GFP_KERNEL);
132	if (!bl)
133		return -ENOMEM;
134
135	bl->lp = lp;
136
137	platform_set_drvdata(pdev, bl);
138
139	ret = lp8788_backlight_configure(bl);
140	if (ret) {
141		dev_err(lp->dev, "backlight config err: %d\n", ret);
142		goto err_dev;
143	}
144
145	ret = lp8788_backlight_register(bl);
146	if (ret) {
147		dev_err(lp->dev, "register backlight err: %d\n", ret);
148		goto err_dev;
149	}
150
151	ret = sysfs_create_group(&pdev->dev.kobj, &lp8788_attr_group);
152	if (ret) {
153		dev_err(lp->dev, "register sysfs err: %d\n", ret);
154		goto err_sysfs;
155	}
156
157	backlight_update_status(bl->bl_dev);
158
159	return 0;
160
161err_sysfs:
162	lp8788_backlight_unregister(bl);
163err_dev:
164	return ret;
165}
166
167static void lp8788_backlight_remove(struct platform_device *pdev)
168{
169	struct lp8788_bl *bl = platform_get_drvdata(pdev);
170	struct backlight_device *bl_dev = bl->bl_dev;
171
172	bl_dev->props.brightness = 0;
173	backlight_update_status(bl_dev);
174	sysfs_remove_group(&pdev->dev.kobj, &lp8788_attr_group);
175	lp8788_backlight_unregister(bl);
176}
177
178static struct platform_driver lp8788_bl_driver = {
179	.probe = lp8788_backlight_probe,
180	.remove = lp8788_backlight_remove,
181	.driver = {
182		.name = LP8788_DEV_BACKLIGHT,
183	},
184};
185module_platform_driver(lp8788_bl_driver);
186
187MODULE_DESCRIPTION("Texas Instruments LP8788 Backlight Driver");
188MODULE_AUTHOR("Milo Kim");
189MODULE_LICENSE("GPL");
190MODULE_ALIAS("platform:lp8788-backlight");