1 /*
2  * TI LP8788 MFD - backlight driver
3  *
4  * Copyright 2012 Texas Instruments
5  *
6  * Author: Milo(Woogyom) Kim <milo.kim@ti.com>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  *
12  */
13 
14 #include <linux/backlight.h>
15 #include <linux/err.h>
16 #include <linux/mfd/lp8788.h>
17 #include <linux/module.h>
18 #include <linux/platform_device.h>
19 #include <linux/pwm.h>
20 #include <linux/slab.h>
21 
22 /* Register address */
23 #define LP8788_BL_CONFIG		0x96
24 #define LP8788_BL_EN			BIT(0)
25 #define LP8788_BL_PWM_INPUT_EN		BIT(5)
26 #define LP8788_BL_FULLSCALE_SHIFT	2
27 #define LP8788_BL_DIM_MODE_SHIFT	1
28 #define LP8788_BL_PWM_POLARITY_SHIFT	6
29 
30 #define LP8788_BL_BRIGHTNESS		0x97
31 
32 #define LP8788_BL_RAMP			0x98
33 #define LP8788_BL_RAMP_RISE_SHIFT	4
34 
35 #define MAX_BRIGHTNESS			127
36 #define DEFAULT_BL_NAME			"lcd-backlight"
37 
38 struct lp8788_bl_config {
39 	enum lp8788_bl_ctrl_mode bl_mode;
40 	enum lp8788_bl_dim_mode dim_mode;
41 	enum lp8788_bl_full_scale_current full_scale;
42 	enum lp8788_bl_ramp_step rise_time;
43 	enum lp8788_bl_ramp_step fall_time;
44 	enum pwm_polarity pwm_pol;
45 };
46 
47 struct lp8788_bl {
48 	struct lp8788 *lp;
49 	struct backlight_device *bl_dev;
50 	struct lp8788_backlight_platform_data *pdata;
51 	enum lp8788_bl_ctrl_mode mode;
52 	struct pwm_device *pwm;
53 };
54 
55 static struct lp8788_bl_config default_bl_config = {
56 	.bl_mode    = LP8788_BL_REGISTER_ONLY,
57 	.dim_mode   = LP8788_DIM_EXPONENTIAL,
58 	.full_scale = LP8788_FULLSCALE_1900uA,
59 	.rise_time  = LP8788_RAMP_8192us,
60 	.fall_time  = LP8788_RAMP_8192us,
61 	.pwm_pol    = PWM_POLARITY_NORMAL,
62 };
63 
64 static inline bool is_brightness_ctrl_by_pwm(enum lp8788_bl_ctrl_mode mode)
65 {
66 	return mode == LP8788_BL_COMB_PWM_BASED;
67 }
68 
69 static inline bool is_brightness_ctrl_by_register(enum lp8788_bl_ctrl_mode mode)
70 {
71 	return mode == LP8788_BL_REGISTER_ONLY ||
72 		mode == LP8788_BL_COMB_REGISTER_BASED;
73 }
74 
75 static int lp8788_backlight_configure(struct lp8788_bl *bl)
76 {
77 	struct lp8788_backlight_platform_data *pdata = bl->pdata;
78 	struct lp8788_bl_config *cfg = &default_bl_config;
79 	int ret;
80 	u8 val;
81 
82 	/*
83 	 * Update chip configuration if platform data exists,
84 	 * otherwise use the default settings.
85 	 */
86 	if (pdata) {
87 		cfg->bl_mode    = pdata->bl_mode;
88 		cfg->dim_mode   = pdata->dim_mode;
89 		cfg->full_scale = pdata->full_scale;
90 		cfg->rise_time  = pdata->rise_time;
91 		cfg->fall_time  = pdata->fall_time;
92 		cfg->pwm_pol    = pdata->pwm_pol;
93 	}
94 
95 	/* Brightness ramp up/down */
96 	val = (cfg->rise_time << LP8788_BL_RAMP_RISE_SHIFT) | cfg->fall_time;
97 	ret = lp8788_write_byte(bl->lp, LP8788_BL_RAMP, val);
98 	if (ret)
99 		return ret;
100 
101 	/* Fullscale current setting */
102 	val = (cfg->full_scale << LP8788_BL_FULLSCALE_SHIFT) |
103 		(cfg->dim_mode << LP8788_BL_DIM_MODE_SHIFT);
104 
105 	/* Brightness control mode */
106 	switch (cfg->bl_mode) {
107 	case LP8788_BL_REGISTER_ONLY:
108 		val |= LP8788_BL_EN;
109 		break;
110 	case LP8788_BL_COMB_PWM_BASED:
111 	case LP8788_BL_COMB_REGISTER_BASED:
112 		val |= LP8788_BL_EN | LP8788_BL_PWM_INPUT_EN |
113 			(cfg->pwm_pol << LP8788_BL_PWM_POLARITY_SHIFT);
114 		break;
115 	default:
116 		dev_err(bl->lp->dev, "invalid mode: %d\n", cfg->bl_mode);
117 		return -EINVAL;
118 	}
119 
120 	bl->mode = cfg->bl_mode;
121 
122 	return lp8788_write_byte(bl->lp, LP8788_BL_CONFIG, val);
123 }
124 
125 static void lp8788_pwm_ctrl(struct lp8788_bl *bl, int br, int max_br)
126 {
127 	unsigned int period;
128 	unsigned int duty;
129 	struct device *dev;
130 	struct pwm_device *pwm;
131 
132 	if (!bl->pdata)
133 		return;
134 
135 	period = bl->pdata->period_ns;
136 	duty = br * period / max_br;
137 	dev = bl->lp->dev;
138 
139 	/* request PWM device with the consumer name */
140 	if (!bl->pwm) {
141 		pwm = devm_pwm_get(dev, LP8788_DEV_BACKLIGHT);
142 		if (IS_ERR(pwm)) {
143 			dev_err(dev, "can not get PWM device\n");
144 			return;
145 		}
146 
147 		bl->pwm = pwm;
148 	}
149 
150 	pwm_config(bl->pwm, duty, period);
151 	if (duty)
152 		pwm_enable(bl->pwm);
153 	else
154 		pwm_disable(bl->pwm);
155 }
156 
157 static int lp8788_bl_update_status(struct backlight_device *bl_dev)
158 {
159 	struct lp8788_bl *bl = bl_get_data(bl_dev);
160 	enum lp8788_bl_ctrl_mode mode = bl->mode;
161 
162 	if (bl_dev->props.state & BL_CORE_SUSPENDED)
163 		bl_dev->props.brightness = 0;
164 
165 	if (is_brightness_ctrl_by_pwm(mode)) {
166 		int brt = bl_dev->props.brightness;
167 		int max = bl_dev->props.max_brightness;
168 
169 		lp8788_pwm_ctrl(bl, brt, max);
170 	} else if (is_brightness_ctrl_by_register(mode)) {
171 		u8 brt = bl_dev->props.brightness;
172 
173 		lp8788_write_byte(bl->lp, LP8788_BL_BRIGHTNESS, brt);
174 	}
175 
176 	return 0;
177 }
178 
179 static const struct backlight_ops lp8788_bl_ops = {
180 	.options = BL_CORE_SUSPENDRESUME,
181 	.update_status = lp8788_bl_update_status,
182 };
183 
184 static int lp8788_backlight_register(struct lp8788_bl *bl)
185 {
186 	struct backlight_device *bl_dev;
187 	struct backlight_properties props;
188 	struct lp8788_backlight_platform_data *pdata = bl->pdata;
189 	int init_brt;
190 	char *name;
191 
192 	props.type = BACKLIGHT_PLATFORM;
193 	props.max_brightness = MAX_BRIGHTNESS;
194 
195 	/* Initial brightness */
196 	if (pdata)
197 		init_brt = min_t(int, pdata->initial_brightness,
198 				props.max_brightness);
199 	else
200 		init_brt = 0;
201 
202 	props.brightness = init_brt;
203 
204 	/* Backlight device name */
205 	if (!pdata || !pdata->name)
206 		name = DEFAULT_BL_NAME;
207 	else
208 		name = pdata->name;
209 
210 	bl_dev = backlight_device_register(name, bl->lp->dev, bl,
211 				       &lp8788_bl_ops, &props);
212 	if (IS_ERR(bl_dev))
213 		return PTR_ERR(bl_dev);
214 
215 	bl->bl_dev = bl_dev;
216 
217 	return 0;
218 }
219 
220 static void lp8788_backlight_unregister(struct lp8788_bl *bl)
221 {
222 	struct backlight_device *bl_dev = bl->bl_dev;
223 
224 	if (bl_dev)
225 		backlight_device_unregister(bl_dev);
226 }
227 
228 static ssize_t lp8788_get_bl_ctl_mode(struct device *dev,
229 				     struct device_attribute *attr, char *buf)
230 {
231 	struct lp8788_bl *bl = dev_get_drvdata(dev);
232 	enum lp8788_bl_ctrl_mode mode = bl->mode;
233 	char *strmode;
234 
235 	if (is_brightness_ctrl_by_pwm(mode))
236 		strmode = "PWM based";
237 	else if (is_brightness_ctrl_by_register(mode))
238 		strmode = "Register based";
239 	else
240 		strmode = "Invalid mode";
241 
242 	return scnprintf(buf, PAGE_SIZE, "%s\n", strmode);
243 }
244 
245 static DEVICE_ATTR(bl_ctl_mode, S_IRUGO, lp8788_get_bl_ctl_mode, NULL);
246 
247 static struct attribute *lp8788_attributes[] = {
248 	&dev_attr_bl_ctl_mode.attr,
249 	NULL,
250 };
251 
252 static const struct attribute_group lp8788_attr_group = {
253 	.attrs = lp8788_attributes,
254 };
255 
256 static int lp8788_backlight_probe(struct platform_device *pdev)
257 {
258 	struct lp8788 *lp = dev_get_drvdata(pdev->dev.parent);
259 	struct lp8788_bl *bl;
260 	int ret;
261 
262 	bl = devm_kzalloc(lp->dev, sizeof(struct lp8788_bl), GFP_KERNEL);
263 	if (!bl)
264 		return -ENOMEM;
265 
266 	bl->lp = lp;
267 	if (lp->pdata)
268 		bl->pdata = lp->pdata->bl_pdata;
269 
270 	platform_set_drvdata(pdev, bl);
271 
272 	ret = lp8788_backlight_configure(bl);
273 	if (ret) {
274 		dev_err(lp->dev, "backlight config err: %d\n", ret);
275 		goto err_dev;
276 	}
277 
278 	ret = lp8788_backlight_register(bl);
279 	if (ret) {
280 		dev_err(lp->dev, "register backlight err: %d\n", ret);
281 		goto err_dev;
282 	}
283 
284 	ret = sysfs_create_group(&pdev->dev.kobj, &lp8788_attr_group);
285 	if (ret) {
286 		dev_err(lp->dev, "register sysfs err: %d\n", ret);
287 		goto err_sysfs;
288 	}
289 
290 	backlight_update_status(bl->bl_dev);
291 
292 	return 0;
293 
294 err_sysfs:
295 	lp8788_backlight_unregister(bl);
296 err_dev:
297 	return ret;
298 }
299 
300 static int lp8788_backlight_remove(struct platform_device *pdev)
301 {
302 	struct lp8788_bl *bl = platform_get_drvdata(pdev);
303 	struct backlight_device *bl_dev = bl->bl_dev;
304 
305 	bl_dev->props.brightness = 0;
306 	backlight_update_status(bl_dev);
307 	sysfs_remove_group(&pdev->dev.kobj, &lp8788_attr_group);
308 	lp8788_backlight_unregister(bl);
309 
310 	return 0;
311 }
312 
313 static struct platform_driver lp8788_bl_driver = {
314 	.probe = lp8788_backlight_probe,
315 	.remove = lp8788_backlight_remove,
316 	.driver = {
317 		.name = LP8788_DEV_BACKLIGHT,
318 	},
319 };
320 module_platform_driver(lp8788_bl_driver);
321 
322 MODULE_DESCRIPTION("Texas Instruments LP8788 Backlight Driver");
323 MODULE_AUTHOR("Milo Kim");
324 MODULE_LICENSE("GPL");
325 MODULE_ALIAS("platform:lp8788-backlight");
326