1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * gpio_backlight.c - Simple GPIO-controlled backlight 4 */ 5 6 #include <linux/backlight.h> 7 #include <linux/err.h> 8 #include <linux/fb.h> 9 #include <linux/gpio.h> /* Only for legacy support */ 10 #include <linux/gpio/consumer.h> 11 #include <linux/init.h> 12 #include <linux/kernel.h> 13 #include <linux/module.h> 14 #include <linux/of.h> 15 #include <linux/of_gpio.h> 16 #include <linux/platform_data/gpio_backlight.h> 17 #include <linux/platform_device.h> 18 #include <linux/property.h> 19 #include <linux/slab.h> 20 21 struct gpio_backlight { 22 struct device *dev; 23 struct device *fbdev; 24 25 struct gpio_desc *gpiod; 26 int def_value; 27 }; 28 29 static int gpio_backlight_update_status(struct backlight_device *bl) 30 { 31 struct gpio_backlight *gbl = bl_get_data(bl); 32 int brightness = bl->props.brightness; 33 34 if (bl->props.power != FB_BLANK_UNBLANK || 35 bl->props.fb_blank != FB_BLANK_UNBLANK || 36 bl->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK)) 37 brightness = 0; 38 39 gpiod_set_value_cansleep(gbl->gpiod, brightness); 40 41 return 0; 42 } 43 44 static int gpio_backlight_check_fb(struct backlight_device *bl, 45 struct fb_info *info) 46 { 47 struct gpio_backlight *gbl = bl_get_data(bl); 48 49 return gbl->fbdev == NULL || gbl->fbdev == info->dev; 50 } 51 52 static const struct backlight_ops gpio_backlight_ops = { 53 .options = BL_CORE_SUSPENDRESUME, 54 .update_status = gpio_backlight_update_status, 55 .check_fb = gpio_backlight_check_fb, 56 }; 57 58 static int gpio_backlight_probe_dt(struct platform_device *pdev, 59 struct gpio_backlight *gbl) 60 { 61 struct device *dev = &pdev->dev; 62 int ret; 63 64 gbl->def_value = device_property_read_bool(dev, "default-on"); 65 66 gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS); 67 if (IS_ERR(gbl->gpiod)) { 68 ret = PTR_ERR(gbl->gpiod); 69 70 if (ret != -EPROBE_DEFER) { 71 dev_err(dev, 72 "Error: The gpios parameter is missing or invalid.\n"); 73 } 74 return ret; 75 } 76 77 return 0; 78 } 79 80 static int gpio_backlight_initial_power_state(struct gpio_backlight *gbl) 81 { 82 struct device_node *node = gbl->dev->of_node; 83 84 /* Not booted with device tree or no phandle link to the node */ 85 if (!node || !node->phandle) 86 return gbl->def_value ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN; 87 88 /* if the enable GPIO is disabled, do not enable the backlight */ 89 if (gpiod_get_value_cansleep(gbl->gpiod) == 0) 90 return FB_BLANK_POWERDOWN; 91 92 return FB_BLANK_UNBLANK; 93 } 94 95 96 static int gpio_backlight_probe(struct platform_device *pdev) 97 { 98 struct gpio_backlight_platform_data *pdata = 99 dev_get_platdata(&pdev->dev); 100 struct backlight_properties props; 101 struct backlight_device *bl; 102 struct gpio_backlight *gbl; 103 int ret; 104 105 gbl = devm_kzalloc(&pdev->dev, sizeof(*gbl), GFP_KERNEL); 106 if (gbl == NULL) 107 return -ENOMEM; 108 109 gbl->dev = &pdev->dev; 110 111 if (pdev->dev.fwnode) { 112 ret = gpio_backlight_probe_dt(pdev, gbl); 113 if (ret) 114 return ret; 115 } else if (pdata) { 116 /* 117 * Legacy platform data GPIO retrieveal. Do not expand 118 * the use of this code path, currently only used by one 119 * SH board. 120 */ 121 unsigned long flags = GPIOF_DIR_OUT; 122 123 gbl->fbdev = pdata->fbdev; 124 gbl->def_value = pdata->def_value; 125 flags |= gbl->def_value ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW; 126 127 ret = devm_gpio_request_one(gbl->dev, pdata->gpio, flags, 128 pdata ? pdata->name : "backlight"); 129 if (ret < 0) { 130 dev_err(&pdev->dev, "unable to request GPIO\n"); 131 return ret; 132 } 133 gbl->gpiod = gpio_to_desc(pdata->gpio); 134 if (!gbl->gpiod) 135 return -EINVAL; 136 } else { 137 dev_err(&pdev->dev, 138 "failed to find platform data or device tree node.\n"); 139 return -ENODEV; 140 } 141 142 memset(&props, 0, sizeof(props)); 143 props.type = BACKLIGHT_RAW; 144 props.max_brightness = 1; 145 bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev), 146 &pdev->dev, gbl, &gpio_backlight_ops, 147 &props); 148 if (IS_ERR(bl)) { 149 dev_err(&pdev->dev, "failed to register backlight\n"); 150 return PTR_ERR(bl); 151 } 152 153 bl->props.power = gpio_backlight_initial_power_state(gbl); 154 bl->props.brightness = 1; 155 156 backlight_update_status(bl); 157 158 platform_set_drvdata(pdev, bl); 159 return 0; 160 } 161 162 static struct of_device_id gpio_backlight_of_match[] = { 163 { .compatible = "gpio-backlight" }, 164 { /* sentinel */ } 165 }; 166 167 MODULE_DEVICE_TABLE(of, gpio_backlight_of_match); 168 169 static struct platform_driver gpio_backlight_driver = { 170 .driver = { 171 .name = "gpio-backlight", 172 .of_match_table = gpio_backlight_of_match, 173 }, 174 .probe = gpio_backlight_probe, 175 }; 176 177 module_platform_driver(gpio_backlight_driver); 178 179 MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); 180 MODULE_DESCRIPTION("GPIO-based Backlight Driver"); 181 MODULE_LICENSE("GPL"); 182 MODULE_ALIAS("platform:gpio-backlight"); 183