1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Miscellaneous procedures for dealing with the PowerMac hardware.
4  * Contains support for the backlight.
5  *
6  *   Copyright (C) 2000 Benjamin Herrenschmidt
7  *   Copyright (C) 2006 Michael Hanselmann <linux-kernel@hansmi.ch>
8  *
9  */
10 
11 #include <linux/kernel.h>
12 #include <linux/fb.h>
13 #include <linux/backlight.h>
14 #include <linux/adb.h>
15 #include <linux/pmu.h>
16 #include <linux/atomic.h>
17 #include <linux/export.h>
18 #include <asm/backlight.h>
19 
20 #define OLD_BACKLIGHT_MAX 15
21 
22 static void pmac_backlight_key_worker(struct work_struct *work);
23 static void pmac_backlight_set_legacy_worker(struct work_struct *work);
24 
25 static DECLARE_WORK(pmac_backlight_key_work, pmac_backlight_key_worker);
26 static DECLARE_WORK(pmac_backlight_set_legacy_work, pmac_backlight_set_legacy_worker);
27 
28 /* Although these variables are used in interrupt context, it makes no sense to
29  * protect them. No user is able to produce enough key events per second and
30  * notice the errors that might happen.
31  */
32 static int pmac_backlight_key_queued;
33 static int pmac_backlight_set_legacy_queued;
34 
35 /* The via-pmu code allows the backlight to be grabbed, in which case the
36  * in-kernel control of the brightness needs to be disabled. This should
37  * only be used by really old PowerBooks.
38  */
39 static atomic_t kernel_backlight_disabled = ATOMIC_INIT(0);
40 
41 /* Protect the pmac_backlight variable below.
42    You should hold this lock when using the pmac_backlight pointer to
43    prevent its potential removal. */
44 DEFINE_MUTEX(pmac_backlight_mutex);
45 
46 /* Main backlight storage
47  *
48  * Backlight drivers in this variable are required to have the "ops"
49  * attribute set and to have an update_status function.
50  *
51  * We can only store one backlight here, but since Apple laptops have only one
52  * internal display, it doesn't matter. Other backlight drivers can be used
53  * independently.
54  *
55  */
56 struct backlight_device *pmac_backlight;
57 
58 int pmac_has_backlight_type(const char *type)
59 {
60 	struct device_node* bk_node = of_find_node_by_name(NULL, "backlight");
61 
62 	if (bk_node) {
63 		const char *prop = of_get_property(bk_node,
64 				"backlight-control", NULL);
65 		if (prop && strncmp(prop, type, strlen(type)) == 0) {
66 			of_node_put(bk_node);
67 			return 1;
68 		}
69 		of_node_put(bk_node);
70 	}
71 
72 	return 0;
73 }
74 
75 int pmac_backlight_curve_lookup(struct fb_info *info, int value)
76 {
77 	int level = (FB_BACKLIGHT_LEVELS - 1);
78 
79 	if (info && info->bl_dev) {
80 		int i, max = 0;
81 
82 		/* Look for biggest value */
83 		for (i = 0; i < FB_BACKLIGHT_LEVELS; i++)
84 			max = max((int)info->bl_curve[i], max);
85 
86 		/* Look for nearest value */
87 		for (i = 0; i < FB_BACKLIGHT_LEVELS; i++) {
88 			int diff = abs(info->bl_curve[i] - value);
89 			if (diff < max) {
90 				max = diff;
91 				level = i;
92 			}
93 		}
94 
95 	}
96 
97 	return level;
98 }
99 
100 static void pmac_backlight_key_worker(struct work_struct *work)
101 {
102 	if (atomic_read(&kernel_backlight_disabled))
103 		return;
104 
105 	mutex_lock(&pmac_backlight_mutex);
106 	if (pmac_backlight) {
107 		struct backlight_properties *props;
108 		int brightness;
109 
110 		props = &pmac_backlight->props;
111 
112 		brightness = props->brightness +
113 			((pmac_backlight_key_queued?-1:1) *
114 			 (props->max_brightness / 15));
115 
116 		if (brightness < 0)
117 			brightness = 0;
118 		else if (brightness > props->max_brightness)
119 			brightness = props->max_brightness;
120 
121 		props->brightness = brightness;
122 		backlight_update_status(pmac_backlight);
123 	}
124 	mutex_unlock(&pmac_backlight_mutex);
125 }
126 
127 /* This function is called in interrupt context */
128 void pmac_backlight_key(int direction)
129 {
130 	if (atomic_read(&kernel_backlight_disabled))
131 		return;
132 
133 	/* we can receive multiple interrupts here, but the scheduled work
134 	 * will run only once, with the last value
135 	 */
136 	pmac_backlight_key_queued = direction;
137 	schedule_work(&pmac_backlight_key_work);
138 }
139 
140 static int __pmac_backlight_set_legacy_brightness(int brightness)
141 {
142 	int error = -ENXIO;
143 
144 	mutex_lock(&pmac_backlight_mutex);
145 	if (pmac_backlight) {
146 		struct backlight_properties *props;
147 
148 		props = &pmac_backlight->props;
149 		props->brightness = brightness *
150 			(props->max_brightness + 1) /
151 			(OLD_BACKLIGHT_MAX + 1);
152 
153 		if (props->brightness > props->max_brightness)
154 			props->brightness = props->max_brightness;
155 		else if (props->brightness < 0)
156 			props->brightness = 0;
157 
158 		backlight_update_status(pmac_backlight);
159 
160 		error = 0;
161 	}
162 	mutex_unlock(&pmac_backlight_mutex);
163 
164 	return error;
165 }
166 
167 static void pmac_backlight_set_legacy_worker(struct work_struct *work)
168 {
169 	if (atomic_read(&kernel_backlight_disabled))
170 		return;
171 
172 	__pmac_backlight_set_legacy_brightness(pmac_backlight_set_legacy_queued);
173 }
174 
175 /* This function is called in interrupt context */
176 void pmac_backlight_set_legacy_brightness_pmu(int brightness) {
177 	if (atomic_read(&kernel_backlight_disabled))
178 		return;
179 
180 	pmac_backlight_set_legacy_queued = brightness;
181 	schedule_work(&pmac_backlight_set_legacy_work);
182 }
183 
184 int pmac_backlight_set_legacy_brightness(int brightness)
185 {
186 	return __pmac_backlight_set_legacy_brightness(brightness);
187 }
188 
189 int pmac_backlight_get_legacy_brightness(void)
190 {
191 	int result = -ENXIO;
192 
193 	mutex_lock(&pmac_backlight_mutex);
194 	if (pmac_backlight) {
195 		struct backlight_properties *props;
196 
197 		props = &pmac_backlight->props;
198 
199 		result = props->brightness *
200 			(OLD_BACKLIGHT_MAX + 1) /
201 			(props->max_brightness + 1);
202 	}
203 	mutex_unlock(&pmac_backlight_mutex);
204 
205 	return result;
206 }
207 
208 void pmac_backlight_disable(void)
209 {
210 	atomic_inc(&kernel_backlight_disabled);
211 }
212 
213 void pmac_backlight_enable(void)
214 {
215 	atomic_dec(&kernel_backlight_disabled);
216 }
217 
218 EXPORT_SYMBOL_GPL(pmac_backlight);
219 EXPORT_SYMBOL_GPL(pmac_backlight_mutex);
220 EXPORT_SYMBOL_GPL(pmac_has_backlight_type);
221