1 // SPDX-License-Identifier: GPL-2.0-only
3  * Backlight driver for the Kinetic KTD253
4  * Based on code and know-how from the Samsung GT-S7710
7 #include <linux/backlight.h>
11 #include <linux/gpio/consumer.h>
40 	gpiod_set_value_cansleep(ktd253->gpiod, 1);  in ktd253_backlight_set_max_ratio()
48 	 * These GPIO operations absolutely can NOT sleep so no _cansleep  in ktd253_backlight_stepdown()
49 	 * suffixes, and no using GPIO expanders on slow buses for this!  in ktd253_backlight_stepdown()
58 	 * top so we have the backlight in a known state.  in ktd253_backlight_stepdown()
63 	gpiod_set_value(ktd253->gpiod, 0);  in ktd253_backlight_stepdown()
65 	gpiod_set_value(ktd253->gpiod, 1);  in ktd253_backlight_stepdown()
66 	ns = ktime_get_ns() - ns;  in ktd253_backlight_stepdown()
68 		dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns);  in ktd253_backlight_stepdown()
69 		return -EAGAIN;  in ktd253_backlight_stepdown()
80 	u16 current_ratio = ktd253->ratio;  in ktd253_backlight_update_status()
83 	dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);  in ktd253_backlight_update_status()
92 		gpiod_set_value_cansleep(ktd253->gpiod, 0);  in ktd253_backlight_update_status()
94 		 * We need to keep the GPIO low for at least this long  in ktd253_backlight_update_status()
98 		ktd253->ratio = 0;  in ktd253_backlight_update_status()
109 		 * These GPIO operations absolutely can NOT sleep so no  in ktd253_backlight_update_status()
110 		 * _cansleep suffixes, and no using GPIO expanders on  in ktd253_backlight_update_status()
114 		if (ret == -EAGAIN) {  in ktd253_backlight_update_status()
116 			 * Something disturbed the backlight setting code when  in ktd253_backlight_update_status()
120 			gpiod_set_value_cansleep(ktd253->gpiod, 0);  in ktd253_backlight_update_status()
128 			current_ratio--;  in ktd253_backlight_update_status()
131 	ktd253->ratio = current_ratio;  in ktd253_backlight_update_status()
133 	dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);  in ktd253_backlight_update_status()
145 	struct device *dev = &pdev->dev;  in ktd253_backlight_probe()
154 		return -ENOMEM;  in ktd253_backlight_probe()
155 	ktd253->dev = dev;  in ktd253_backlight_probe()
157 	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);  in ktd253_backlight_probe()
166 	ret = device_property_read_u32(dev, "default-brightness", &brightness);  in ktd253_backlight_probe()
175 	ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);  in ktd253_backlight_probe()
176 	if (IS_ERR(ktd253->gpiod))  in ktd253_backlight_probe()
177 		return dev_err_probe(dev, PTR_ERR(ktd253->gpiod),  in ktd253_backlight_probe()
178 				     "gpio line missing or invalid.\n");  in ktd253_backlight_probe()
179 	gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));  in ktd253_backlight_probe()
180 	/* Bring backlight to a known off state */  in ktd253_backlight_probe()
186 		dev_err(dev, "failed to register backlight\n");  in ktd253_backlight_probe()
189 	bl->props.max_brightness = max_brightness;  in ktd253_backlight_probe()
190 	/* When we just enable the GPIO line we set max brightness */  in ktd253_backlight_probe()
192 		bl->props.brightness = brightness;  in ktd253_backlight_probe()
193 		bl->props.power = FB_BLANK_UNBLANK;  in ktd253_backlight_probe()
195 		bl->props.brightness = 0;  in ktd253_backlight_probe()
196 		bl->props.power = FB_BLANK_POWERDOWN;  in ktd253_backlight_probe()
199 	ktd253->bl = bl;  in ktd253_backlight_probe()
215 		.name = "ktd253-backlight",
223 MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
225 MODULE_ALIAS("platform:ktd253-backlight");