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