drivers/video/backlight/gpio_backlight.c

   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");