1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Driver for the Cirrus EP93xx lcd backlight
4  *
5  * Copyright (c) 2010 H Hartley Sweeten <hsweeten@visionengravers.com>
6  *
7  * This driver controls the pulse width modulated brightness control output,
8  * BRIGHT, on the Cirrus EP9307, EP9312, and EP9315 processors.
9  */
10 
11 #include <linux/module.h>
12 #include <linux/platform_device.h>
13 #include <linux/io.h>
14 #include <linux/fb.h>
15 #include <linux/backlight.h>
16 
17 #define EP93XX_MAX_COUNT		255
18 #define EP93XX_MAX_BRIGHT		255
19 #define EP93XX_DEF_BRIGHT		128
20 
21 struct ep93xxbl {
22 	void __iomem *mmio;
23 	int brightness;
24 };
25 
26 static int ep93xxbl_set(struct backlight_device *bl, int brightness)
27 {
28 	struct ep93xxbl *ep93xxbl = bl_get_data(bl);
29 
30 	writel((brightness << 8) | EP93XX_MAX_COUNT, ep93xxbl->mmio);
31 
32 	ep93xxbl->brightness = brightness;
33 
34 	return 0;
35 }
36 
37 static int ep93xxbl_update_status(struct backlight_device *bl)
38 {
39 	return ep93xxbl_set(bl, backlight_get_brightness(bl));
40 }
41 
42 static int ep93xxbl_get_brightness(struct backlight_device *bl)
43 {
44 	struct ep93xxbl *ep93xxbl = bl_get_data(bl);
45 
46 	return ep93xxbl->brightness;
47 }
48 
49 static const struct backlight_ops ep93xxbl_ops = {
50 	.update_status	= ep93xxbl_update_status,
51 	.get_brightness	= ep93xxbl_get_brightness,
52 };
53 
54 static int ep93xxbl_probe(struct platform_device *dev)
55 {
56 	struct ep93xxbl *ep93xxbl;
57 	struct backlight_device *bl;
58 	struct backlight_properties props;
59 	struct resource *res;
60 
61 	ep93xxbl = devm_kzalloc(&dev->dev, sizeof(*ep93xxbl), GFP_KERNEL);
62 	if (!ep93xxbl)
63 		return -ENOMEM;
64 
65 	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
66 	if (!res)
67 		return -ENXIO;
68 
69 	/*
70 	 * FIXME - We don't do a request_mem_region here because we are
71 	 * sharing the register space with the framebuffer driver (see
72 	 * drivers/video/ep93xx-fb.c) and doing so will cause the second
73 	 * loaded driver to return -EBUSY.
74 	 *
75 	 * NOTE: No locking is required; the framebuffer does not touch
76 	 * this register.
77 	 */
78 	ep93xxbl->mmio = devm_ioremap(&dev->dev, res->start,
79 				      resource_size(res));
80 	if (!ep93xxbl->mmio)
81 		return -ENXIO;
82 
83 	memset(&props, 0, sizeof(struct backlight_properties));
84 	props.type = BACKLIGHT_RAW;
85 	props.max_brightness = EP93XX_MAX_BRIGHT;
86 	bl = devm_backlight_device_register(&dev->dev, dev->name, &dev->dev,
87 					ep93xxbl, &ep93xxbl_ops, &props);
88 	if (IS_ERR(bl))
89 		return PTR_ERR(bl);
90 
91 	bl->props.brightness = EP93XX_DEF_BRIGHT;
92 
93 	platform_set_drvdata(dev, bl);
94 
95 	ep93xxbl_update_status(bl);
96 
97 	return 0;
98 }
99 
100 #ifdef CONFIG_PM_SLEEP
101 static int ep93xxbl_suspend(struct device *dev)
102 {
103 	struct backlight_device *bl = dev_get_drvdata(dev);
104 
105 	return ep93xxbl_set(bl, 0);
106 }
107 
108 static int ep93xxbl_resume(struct device *dev)
109 {
110 	struct backlight_device *bl = dev_get_drvdata(dev);
111 
112 	backlight_update_status(bl);
113 	return 0;
114 }
115 #endif
116 
117 static SIMPLE_DEV_PM_OPS(ep93xxbl_pm_ops, ep93xxbl_suspend, ep93xxbl_resume);
118 
119 static struct platform_driver ep93xxbl_driver = {
120 	.driver		= {
121 		.name	= "ep93xx-bl",
122 		.pm	= &ep93xxbl_pm_ops,
123 	},
124 	.probe		= ep93xxbl_probe,
125 };
126 
127 module_platform_driver(ep93xxbl_driver);
128 
129 MODULE_DESCRIPTION("EP93xx Backlight Driver");
130 MODULE_AUTHOR("H Hartley Sweeten <hsweeten@visionengravers.com>");
131 MODULE_LICENSE("GPL");
132 MODULE_ALIAS("platform:ep93xx-bl");
133