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>
10 #include <linux/gpio/consumer.h>
39 	gpiod_set_value_cansleep(ktd253->gpiod, 1);  in ktd253_backlight_set_max_ratio()
47 	 * These GPIO operations absolutely can NOT sleep so no _cansleep  in ktd253_backlight_stepdown()
48 	 * suffixes, and no using GPIO expanders on slow buses for this!  in ktd253_backlight_stepdown()
57 	 * top so we have the backlight in a known state.  in ktd253_backlight_stepdown()
62 	gpiod_set_value(ktd253->gpiod, 0);  in ktd253_backlight_stepdown()
64 	gpiod_set_value(ktd253->gpiod, 1);  in ktd253_backlight_stepdown()
65 	ns = ktime_get_ns() - ns;  in ktd253_backlight_stepdown()
67 		dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns);  in ktd253_backlight_stepdown()
68 		return -EAGAIN;  in ktd253_backlight_stepdown()
79 	u16 current_ratio = ktd253->ratio;  in ktd253_backlight_update_status()
82 	dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);  in ktd253_backlight_update_status()
91 		gpiod_set_value_cansleep(ktd253->gpiod, 0);  in ktd253_backlight_update_status()
93 		 * We need to keep the GPIO low for at least this long  in ktd253_backlight_update_status()
97 		ktd253->ratio = 0;  in ktd253_backlight_update_status()
108 		 * These GPIO operations absolutely can NOT sleep so no  in ktd253_backlight_update_status()
109 		 * _cansleep suffixes, and no using GPIO expanders on  in ktd253_backlight_update_status()
113 		if (ret == -EAGAIN) {  in ktd253_backlight_update_status()
115 			 * Something disturbed the backlight setting code when  in ktd253_backlight_update_status()
119 			gpiod_set_value_cansleep(ktd253->gpiod, 0);  in ktd253_backlight_update_status()
127 			current_ratio--;  in ktd253_backlight_update_status()
130 	ktd253->ratio = current_ratio;  in ktd253_backlight_update_status()
132 	dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);  in ktd253_backlight_update_status()
144 	struct device *dev = &pdev->dev;  in ktd253_backlight_probe()
153 		return -ENOMEM;  in ktd253_backlight_probe()
154 	ktd253->dev = dev;  in ktd253_backlight_probe()
156 	ret = device_property_read_u32(dev, "max-brightness", &max_brightness);  in ktd253_backlight_probe()
165 	ret = device_property_read_u32(dev, "default-brightness", &brightness);  in ktd253_backlight_probe()
174 	ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);  in ktd253_backlight_probe()
175 	if (IS_ERR(ktd253->gpiod))  in ktd253_backlight_probe()
176 		return dev_err_probe(dev, PTR_ERR(ktd253->gpiod),  in ktd253_backlight_probe()
177 				     "gpio line missing or invalid.\n");  in ktd253_backlight_probe()
178 	gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));  in ktd253_backlight_probe()
179 	/* Bring backlight to a known off state */  in ktd253_backlight_probe()
185 		dev_err(dev, "failed to register backlight\n");  in ktd253_backlight_probe()
188 	bl->props.max_brightness = max_brightness;  in ktd253_backlight_probe()
189 	/* When we just enable the GPIO line we set max brightness */  in ktd253_backlight_probe()
191 		bl->props.brightness = brightness;  in ktd253_backlight_probe()
192 		bl->props.power = BACKLIGHT_POWER_ON;  in ktd253_backlight_probe()
194 		bl->props.brightness = 0;  in ktd253_backlight_probe()
195 		bl->props.power = BACKLIGHT_POWER_OFF;  in ktd253_backlight_probe()
198 	ktd253->bl = bl;  in ktd253_backlight_probe()
214 		.name = "ktd253-backlight",
222 MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
224 MODULE_ALIAS("platform:ktd253-backlight");