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 		 * FIXME: pwm_apply_args() should be removed when switching to
151 		 * the atomic PWM API.
152 		 */
153 		pwm_apply_args(pwm);
154 	}
155 
156 	pwm_config(bl->pwm, duty, period);
157 	if (duty)
158 		pwm_enable(bl->pwm);
159 	else
160 		pwm_disable(bl->pwm);
161 }
162 
163 static int lp8788_bl_update_status(struct backlight_device *bl_dev)
164 {
165 	struct lp8788_bl *bl = bl_get_data(bl_dev);
166 	enum lp8788_bl_ctrl_mode mode = bl->mode;
167 
168 	if (bl_dev->props.state & BL_CORE_SUSPENDED)
169 		bl_dev->props.brightness = 0;
170 
171 	if (is_brightness_ctrl_by_pwm(mode)) {
172 		int brt = bl_dev->props.brightness;
173 		int max = bl_dev->props.max_brightness;
174 
175 		lp8788_pwm_ctrl(bl, brt, max);
176 	} else if (is_brightness_ctrl_by_register(mode)) {
177 		u8 brt = bl_dev->props.brightness;
178 
179 		lp8788_write_byte(bl->lp, LP8788_BL_BRIGHTNESS, brt);
180 	}
181 
182 	return 0;
183 }
184 
185 static const struct backlight_ops lp8788_bl_ops = {
186 	.options = BL_CORE_SUSPENDRESUME,
187 	.update_status = lp8788_bl_update_status,
188 };
189 
190 static int lp8788_backlight_register(struct lp8788_bl *bl)
191 {
192 	struct backlight_device *bl_dev;
193 	struct backlight_properties props;
194 	struct lp8788_backlight_platform_data *pdata = bl->pdata;
195 	int init_brt;
196 	char *name;
197 
198 	props.type = BACKLIGHT_PLATFORM;
199 	props.max_brightness = MAX_BRIGHTNESS;
200 
201 	/* Initial brightness */
202 	if (pdata)
203 		init_brt = min_t(int, pdata->initial_brightness,
204 				props.max_brightness);
205 	else
206 		init_brt = 0;
207 
208 	props.brightness = init_brt;
209 
210 	/* Backlight device name */
211 	if (!pdata || !pdata->name)
212 		name = DEFAULT_BL_NAME;
213 	else
214 		name = pdata->name;
215 
216 	bl_dev = backlight_device_register(name, bl->lp->dev, bl,
217 				       &lp8788_bl_ops, &props);
218 	if (IS_ERR(bl_dev))
219 		return PTR_ERR(bl_dev);
220 
221 	bl->bl_dev = bl_dev;
222 
223 	return 0;
224 }
225 
226 static void lp8788_backlight_unregister(struct lp8788_bl *bl)
227 {
228 	struct backlight_device *bl_dev = bl->bl_dev;
229 
230 	backlight_device_unregister(bl_dev);
231 }
232 
233 static ssize_t lp8788_get_bl_ctl_mode(struct device *dev,
234 				     struct device_attribute *attr, char *buf)
235 {
236 	struct lp8788_bl *bl = dev_get_drvdata(dev);
237 	enum lp8788_bl_ctrl_mode mode = bl->mode;
238 	char *strmode;
239 
240 	if (is_brightness_ctrl_by_pwm(mode))
241 		strmode = "PWM based";
242 	else if (is_brightness_ctrl_by_register(mode))
243 		strmode = "Register based";
244 	else
245 		strmode = "Invalid mode";
246 
247 	return scnprintf(buf, PAGE_SIZE, "%s\n", strmode);
248 }
249 
250 static DEVICE_ATTR(bl_ctl_mode, S_IRUGO, lp8788_get_bl_ctl_mode, NULL);
251 
252 static struct attribute *lp8788_attributes[] = {
253 	&dev_attr_bl_ctl_mode.attr,
254 	NULL,
255 };
256 
257 static const struct attribute_group lp8788_attr_group = {
258 	.attrs = lp8788_attributes,
259 };
260 
261 static int lp8788_backlight_probe(struct platform_device *pdev)
262 {
263 	struct lp8788 *lp = dev_get_drvdata(pdev->dev.parent);
264 	struct lp8788_bl *bl;
265 	int ret;
266 
267 	bl = devm_kzalloc(lp->dev, sizeof(struct lp8788_bl), GFP_KERNEL);
268 	if (!bl)
269 		return -ENOMEM;
270 
271 	bl->lp = lp;
272 	if (lp->pdata)
273 		bl->pdata = lp->pdata->bl_pdata;
274 
275 	platform_set_drvdata(pdev, bl);
276 
277 	ret = lp8788_backlight_configure(bl);
278 	if (ret) {
279 		dev_err(lp->dev, "backlight config err: %d\n", ret);
280 		goto err_dev;
281 	}
282 
283 	ret = lp8788_backlight_register(bl);
284 	if (ret) {
285 		dev_err(lp->dev, "register backlight err: %d\n", ret);
286 		goto err_dev;
287 	}
288 
289 	ret = sysfs_create_group(&pdev->dev.kobj, &lp8788_attr_group);
290 	if (ret) {
291 		dev_err(lp->dev, "register sysfs err: %d\n", ret);
292 		goto err_sysfs;
293 	}
294 
295 	backlight_update_status(bl->bl_dev);
296 
297 	return 0;
298 
299 err_sysfs:
300 	lp8788_backlight_unregister(bl);
301 err_dev:
302 	return ret;
303 }
304 
305 static int lp8788_backlight_remove(struct platform_device *pdev)
306 {
307 	struct lp8788_bl *bl = platform_get_drvdata(pdev);
308 	struct backlight_device *bl_dev = bl->bl_dev;
309 
310 	bl_dev->props.brightness = 0;
311 	backlight_update_status(bl_dev);
312 	sysfs_remove_group(&pdev->dev.kobj, &lp8788_attr_group);
313 	lp8788_backlight_unregister(bl);
314 
315 	return 0;
316 }
317 
318 static struct platform_driver lp8788_bl_driver = {
319 	.probe = lp8788_backlight_probe,
320 	.remove = lp8788_backlight_remove,
321 	.driver = {
322 		.name = LP8788_DEV_BACKLIGHT,
323 	},
324 };
325 module_platform_driver(lp8788_bl_driver);
326 
327 MODULE_DESCRIPTION("Texas Instruments LP8788 Backlight Driver");
328 MODULE_AUTHOR("Milo Kim");
329 MODULE_LICENSE("GPL");
330 MODULE_ALIAS("platform:lp8788-backlight");
331