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7#include <linux/backlight.h>
8#include <linux/delay.h>
9#include <linux/err.h>
10#include <linux/fb.h>
11#include <linux/gpio/consumer.h>
12#include <linux/init.h>
13#include <linux/kernel.h>
14#include <linux/limits.h>
15#include <linux/module.h>
16#include <linux/of.h>
17#include <linux/platform_device.h>
18#include <linux/property.h>
19#include <linux/slab.h>
20
21
22#define KTD253_MIN_RATIO 1
23#define KTD253_MAX_RATIO 32
24#define KTD253_DEFAULT_RATIO 13
25
26#define KTD253_T_LOW_NS (200 + 10)
27#define KTD253_T_HIGH_NS (200 + 10)
28#define KTD253_T_OFF_CRIT_NS 100000
29#define KTD253_T_OFF_MS 3
30
31struct ktd253_backlight {
32 struct device *dev;
33 struct backlight_device *bl;
34 struct gpio_desc *gpiod;
35 u16 ratio;
36};
37
38static void ktd253_backlight_set_max_ratio(struct ktd253_backlight *ktd253)
39{
40 gpiod_set_value_cansleep(ktd253->gpiod, 1);
41 ndelay(KTD253_T_HIGH_NS);
42
43}
44
45static int ktd253_backlight_stepdown(struct ktd253_backlight *ktd253)
46{
47
48
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57
58
59
60 u64 ns;
61
62 ns = ktime_get_ns();
63 gpiod_set_value(ktd253->gpiod, 0);
64 ndelay(KTD253_T_LOW_NS);
65 gpiod_set_value(ktd253->gpiod, 1);
66 ns = ktime_get_ns() - ns;
67 if (ns >= KTD253_T_OFF_CRIT_NS) {
68 dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns);
69 return -EAGAIN;
70 }
71 ndelay(KTD253_T_HIGH_NS);
72 return 0;
73}
74
75static int ktd253_backlight_update_status(struct backlight_device *bl)
76{
77 struct ktd253_backlight *ktd253 = bl_get_data(bl);
78 int brightness = backlight_get_brightness(bl);
79 u16 target_ratio;
80 u16 current_ratio = ktd253->ratio;
81 int ret;
82
83 dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);
84
85 target_ratio = brightness;
86
87 if (target_ratio == current_ratio)
88
89 return 0;
90
91 if (target_ratio == 0) {
92 gpiod_set_value_cansleep(ktd253->gpiod, 0);
93
94
95
96
97 msleep(KTD253_T_OFF_MS);
98 ktd253->ratio = 0;
99 return 0;
100 }
101
102 if (current_ratio == 0) {
103 ktd253_backlight_set_max_ratio(ktd253);
104 current_ratio = KTD253_MAX_RATIO;
105 }
106
107 while (current_ratio != target_ratio) {
108
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111
112
113 ret = ktd253_backlight_stepdown(ktd253);
114 if (ret == -EAGAIN) {
115
116
117
118
119
120 gpiod_set_value_cansleep(ktd253->gpiod, 0);
121 msleep(KTD253_T_OFF_MS);
122 ktd253_backlight_set_max_ratio(ktd253);
123 current_ratio = KTD253_MAX_RATIO;
124 } else if (current_ratio == KTD253_MIN_RATIO) {
125
126 current_ratio = KTD253_MAX_RATIO;
127 } else {
128 current_ratio--;
129 }
130 }
131 ktd253->ratio = current_ratio;
132
133 dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);
134
135 return 0;
136}
137
138static const struct backlight_ops ktd253_backlight_ops = {
139 .options = BL_CORE_SUSPENDRESUME,
140 .update_status = ktd253_backlight_update_status,
141};
142
143static int ktd253_backlight_probe(struct platform_device *pdev)
144{
145 struct device *dev = &pdev->dev;
146 struct backlight_device *bl;
147 struct ktd253_backlight *ktd253;
148 u32 max_brightness;
149 u32 brightness;
150 int ret;
151
152 ktd253 = devm_kzalloc(dev, sizeof(*ktd253), GFP_KERNEL);
153 if (!ktd253)
154 return -ENOMEM;
155 ktd253->dev = dev;
156
157 ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
158 if (ret)
159 max_brightness = KTD253_MAX_RATIO;
160 if (max_brightness > KTD253_MAX_RATIO) {
161
162 dev_err(dev, "illegal max brightness specified\n");
163 max_brightness = KTD253_MAX_RATIO;
164 }
165
166 ret = device_property_read_u32(dev, "default-brightness", &brightness);
167 if (ret)
168 brightness = KTD253_DEFAULT_RATIO;
169 if (brightness > max_brightness) {
170
171 dev_err(dev, "default brightness exceeds max brightness\n");
172 brightness = max_brightness;
173 }
174
175 ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
176 if (IS_ERR(ktd253->gpiod)) {
177 ret = PTR_ERR(ktd253->gpiod);
178 if (ret != -EPROBE_DEFER)
179 dev_err(dev, "gpio line missing or invalid.\n");
180 return ret;
181 }
182 gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));
183
184 msleep(KTD253_T_OFF_MS);
185
186 bl = devm_backlight_device_register(dev, dev_name(dev), dev, ktd253,
187 &ktd253_backlight_ops, NULL);
188 if (IS_ERR(bl)) {
189 dev_err(dev, "failed to register backlight\n");
190 return PTR_ERR(bl);
191 }
192 bl->props.max_brightness = max_brightness;
193
194 if (brightness) {
195 bl->props.brightness = brightness;
196 bl->props.power = FB_BLANK_UNBLANK;
197 } else {
198 bl->props.brightness = 0;
199 bl->props.power = FB_BLANK_POWERDOWN;
200 }
201
202 ktd253->bl = bl;
203 platform_set_drvdata(pdev, bl);
204 backlight_update_status(bl);
205
206 return 0;
207}
208
209static const struct of_device_id ktd253_backlight_of_match[] = {
210 { .compatible = "kinetic,ktd253" },
211 { .compatible = "kinetic,ktd259" },
212 { }
213};
214MODULE_DEVICE_TABLE(of, ktd253_backlight_of_match);
215
216static struct platform_driver ktd253_backlight_driver = {
217 .driver = {
218 .name = "ktd253-backlight",
219 .of_match_table = ktd253_backlight_of_match,
220 },
221 .probe = ktd253_backlight_probe,
222};
223module_platform_driver(ktd253_backlight_driver);
224
225MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
226MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
227MODULE_LICENSE("GPL");
228MODULE_ALIAS("platform:ktd253-backlight");
229