1/*
2 * Backlight driver for Pandora handheld.
3 * Pandora uses TWL4030 PWM0 -> TPS61161 combo for control backlight.
4 * Based on pwm_bl.c
5 *
6 * Copyright 2009,2012 Gražvydas Ignotas <notasas@gmail.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#include <linux/module.h>
14#include <linux/kernel.h>
15#include <linux/platform_device.h>
16#include <linux/delay.h>
17#include <linux/fb.h>
18#include <linux/backlight.h>
19#include <linux/i2c/twl.h>
20#include <linux/err.h>
21
22#define TWL_PWM0_ON		0x00
23#define TWL_PWM0_OFF		0x01
24
25#define TWL_INTBR_GPBR1		0x0c
26#define TWL_INTBR_PMBR1		0x0d
27
28#define TWL_PMBR1_PWM0_MUXMASK	0x0c
29#define TWL_PMBR1_PWM0		0x04
30#define PWM0_CLK_ENABLE		BIT(0)
31#define PWM0_ENABLE		BIT(2)
32
33/* range accepted by hardware */
34#define MIN_VALUE 9
35#define MAX_VALUE 63
36#define MAX_USER_VALUE (MAX_VALUE - MIN_VALUE)
37
38#define PANDORABL_WAS_OFF BL_CORE_DRIVER1
39
40static int pandora_backlight_update_status(struct backlight_device *bl)
41{
42	int brightness = bl->props.brightness;
43	u8 r;
44
45	if (bl->props.power != FB_BLANK_UNBLANK)
46		brightness = 0;
47	if (bl->props.state & BL_CORE_FBBLANK)
48		brightness = 0;
49	if (bl->props.state & BL_CORE_SUSPENDED)
50		brightness = 0;
51
52	if ((unsigned int)brightness > MAX_USER_VALUE)
53		brightness = MAX_USER_VALUE;
54
55	if (brightness == 0) {
56		if (bl->props.state & PANDORABL_WAS_OFF)
57			goto done;
58
59		/* first disable PWM0 output, then clock */
60		twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
61		r &= ~PWM0_ENABLE;
62		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
63		r &= ~PWM0_CLK_ENABLE;
64		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
65
66		goto done;
67	}
68
69	if (bl->props.state & PANDORABL_WAS_OFF) {
70		/*
71		 * set PWM duty cycle to max. TPS61161 seems to use this
72		 * to calibrate it's PWM sensitivity when it starts.
73		 */
74		twl_i2c_write_u8(TWL_MODULE_PWM, MAX_VALUE, TWL_PWM0_OFF);
75
76		/* first enable clock, then PWM0 out */
77		twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_GPBR1);
78		r &= ~PWM0_ENABLE;
79		r |= PWM0_CLK_ENABLE;
80		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
81		r |= PWM0_ENABLE;
82		twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_GPBR1);
83
84		/*
85		 * TI made it very easy to enable digital control, so easy that
86		 * it often triggers unintentionally and disabes PWM control,
87		 * so wait until 1 wire mode detection window ends.
88		 */
89		usleep_range(2000, 10000);
90	}
91
92	twl_i2c_write_u8(TWL_MODULE_PWM, MIN_VALUE + brightness, TWL_PWM0_OFF);
93
94done:
95	if (brightness != 0)
96		bl->props.state &= ~PANDORABL_WAS_OFF;
97	else
98		bl->props.state |= PANDORABL_WAS_OFF;
99
100	return 0;
101}
102
103static const struct backlight_ops pandora_backlight_ops = {
104	.options	= BL_CORE_SUSPENDRESUME,
105	.update_status	= pandora_backlight_update_status,
106};
107
108static int pandora_backlight_probe(struct platform_device *pdev)
109{
110	struct backlight_properties props;
111	struct backlight_device *bl;
112	u8 r;
113
114	memset(&props, 0, sizeof(props));
115	props.max_brightness = MAX_USER_VALUE;
116	props.type = BACKLIGHT_RAW;
117	bl = devm_backlight_device_register(&pdev->dev, pdev->name, &pdev->dev,
118					NULL, &pandora_backlight_ops, &props);
119	if (IS_ERR(bl)) {
120		dev_err(&pdev->dev, "failed to register backlight\n");
121		return PTR_ERR(bl);
122	}
123
124	platform_set_drvdata(pdev, bl);
125
126	/* 64 cycle period, ON position 0 */
127	twl_i2c_write_u8(TWL_MODULE_PWM, 0x80, TWL_PWM0_ON);
128
129	bl->props.state |= PANDORABL_WAS_OFF;
130	bl->props.brightness = MAX_USER_VALUE;
131	backlight_update_status(bl);
132
133	/* enable PWM function in pin mux */
134	twl_i2c_read_u8(TWL4030_MODULE_INTBR, &r, TWL_INTBR_PMBR1);
135	r &= ~TWL_PMBR1_PWM0_MUXMASK;
136	r |= TWL_PMBR1_PWM0;
137	twl_i2c_write_u8(TWL4030_MODULE_INTBR, r, TWL_INTBR_PMBR1);
138
139	return 0;
140}
141
142static struct platform_driver pandora_backlight_driver = {
143	.driver		= {
144		.name	= "pandora-backlight",
145	},
146	.probe		= pandora_backlight_probe,
147};
148
149module_platform_driver(pandora_backlight_driver);
150
151MODULE_AUTHOR("Gražvydas Ignotas <notasas@gmail.com>");
152MODULE_DESCRIPTION("Pandora Backlight Driver");
153MODULE_LICENSE("GPL");
154MODULE_ALIAS("platform:pandora-backlight");
155