1/*
2 * Copyright (C) 2012 Bachmann electronic GmbH
3 *	Christian Gmeiner <christian.gmeiner@gmail.com>
4 *
5 * Backlight driver for ot200 visualisation device from
6 * Bachmann electronic GmbH.
7 *
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 as published by
10 * the Free Software Foundation.
11 */
12
13#include <linux/module.h>
14#include <linux/fb.h>
15#include <linux/backlight.h>
16#include <linux/gpio.h>
17#include <linux/cs5535.h>
18
19static struct cs5535_mfgpt_timer *pwm_timer;
20
21/* this array defines the mapping of brightness in % to pwm frequency */
22static const u8 dim_table[101] = {0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
23				  2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4,
24				  4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9,
25				  10, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16,
26				  17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28,
27				  30, 31, 33, 35, 37, 39, 41, 43, 45, 47, 50,
28				  53, 55, 58, 61, 65, 68, 72, 75, 79, 84, 88,
29				  93, 97, 103, 108, 114, 120, 126, 133, 140,
30				  147, 155, 163};
31
32struct ot200_backlight_data {
33	int current_brightness;
34};
35
36#define GPIO_DIMM	27
37#define SCALE		1
38#define CMP1MODE	0x2	/* compare on GE; output high on compare
39				 * greater than or equal */
40#define PWM_SETUP	(SCALE | CMP1MODE << 6 | MFGPT_SETUP_CNTEN)
41#define MAX_COMP2	163
42
43static int ot200_backlight_update_status(struct backlight_device *bl)
44{
45	struct ot200_backlight_data *data = bl_get_data(bl);
46	int brightness = bl->props.brightness;
47
48	if (bl->props.state & BL_CORE_FBBLANK)
49		brightness = 0;
50
51	/* enable or disable PWM timer */
52	if (brightness == 0)
53		cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, 0);
54	else if (data->current_brightness == 0) {
55		cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
56		cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP,
57			MFGPT_SETUP_CNTEN);
58	}
59
60	/* apply new brightness value */
61	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
62		MAX_COMP2 - dim_table[brightness]);
63	data->current_brightness = brightness;
64
65	return 0;
66}
67
68static int ot200_backlight_get_brightness(struct backlight_device *bl)
69{
70	struct ot200_backlight_data *data = bl_get_data(bl);
71	return data->current_brightness;
72}
73
74static const struct backlight_ops ot200_backlight_ops = {
75	.update_status	= ot200_backlight_update_status,
76	.get_brightness	= ot200_backlight_get_brightness,
77};
78
79static int ot200_backlight_probe(struct platform_device *pdev)
80{
81	struct backlight_device *bl;
82	struct ot200_backlight_data *data;
83	struct backlight_properties props;
84	int retval = 0;
85
86	/* request gpio */
87	if (gpio_request(GPIO_DIMM, "ot200 backlight dimmer") < 0) {
88		dev_err(&pdev->dev, "failed to request GPIO %d\n", GPIO_DIMM);
89		return -ENODEV;
90	}
91
92	/* request timer */
93	pwm_timer = cs5535_mfgpt_alloc_timer(7, MFGPT_DOMAIN_ANY);
94	if (!pwm_timer) {
95		dev_err(&pdev->dev, "MFGPT 7 not available\n");
96		retval = -ENODEV;
97		goto error_mfgpt_alloc;
98	}
99
100	data = kzalloc(sizeof(*data), GFP_KERNEL);
101	if (!data) {
102		retval = -ENOMEM;
103		goto error_kzalloc;
104	}
105
106	/* setup gpio */
107	cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_ENABLE);
108	cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_AUX1);
109
110	/* setup timer */
111	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1, 0);
112	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP2, MAX_COMP2);
113	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, PWM_SETUP);
114
115	data->current_brightness = 100;
116	props.max_brightness = 100;
117	props.brightness = 100;
118	props.type = BACKLIGHT_RAW;
119
120	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, data,
121					&ot200_backlight_ops, &props);
122	if (IS_ERR(bl)) {
123		dev_err(&pdev->dev, "failed to register backlight\n");
124		retval = PTR_ERR(bl);
125		goto error_backlight_device_register;
126	}
127
128	platform_set_drvdata(pdev, bl);
129
130	return 0;
131
132error_backlight_device_register:
133	kfree(data);
134error_kzalloc:
135	cs5535_mfgpt_free_timer(pwm_timer);
136error_mfgpt_alloc:
137	gpio_free(GPIO_DIMM);
138	return retval;
139}
140
141static int ot200_backlight_remove(struct platform_device *pdev)
142{
143	struct backlight_device *bl = platform_get_drvdata(pdev);
144	struct ot200_backlight_data *data = bl_get_data(bl);
145
146	backlight_device_unregister(bl);
147
148	/* on module unload set brightness to 100% */
149	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
150	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
151	cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
152		MAX_COMP2 - dim_table[100]);
153
154	cs5535_mfgpt_free_timer(pwm_timer);
155	gpio_free(GPIO_DIMM);
156
157	kfree(data);
158	return 0;
159}
160
161static struct platform_driver ot200_backlight_driver = {
162	.driver		= {
163		.name	= "ot200-backlight",
164		.owner	= THIS_MODULE,
165	},
166	.probe		= ot200_backlight_probe,
167	.remove		= ot200_backlight_remove,
168};
169
170module_platform_driver(ot200_backlight_driver);
171
172MODULE_DESCRIPTION("backlight driver for ot200 visualisation device");
173MODULE_AUTHOR("Christian Gmeiner <christian.gmeiner@gmail.com>");
174MODULE_LICENSE("GPL");
175MODULE_ALIAS("platform:ot200-backlight");
176