drivers/video/backlight/ot200_bl.c

   1 /*
   2  * Copyright (C) 2012 Bachmann electronic GmbH
   3  *      Christian Gmeiner <christian.gmeiner@gmail.com>
   4  *
   5  * Backlight driver for ot200 visualisation device from
   6  * Bachmann electronic GmbH.
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 as published by
  10  * the Free Software Foundation.
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/fb.h>
  15 #include <linux/backlight.h>
  16 #include <linux/gpio.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/cs5535.h>
  19
  20 static struct cs5535_mfgpt_timer *pwm_timer;
  21
  22 /* this array defines the mapping of brightness in % to pwm frequency */
  23 static const u8 dim_table[101] = {0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
  24                                   2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4,
  25                                   4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 9,
  26                                   10, 10, 11, 11, 12, 12, 13, 14, 15, 15, 16,
  27                                   17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28,
  28                                   30, 31, 33, 35, 37, 39, 41, 43, 45, 47, 50,
  29                                   53, 55, 58, 61, 65, 68, 72, 75, 79, 84, 88,
  30                                   93, 97, 103, 108, 114, 120, 126, 133, 140,
  31                                   147, 155, 163};
  32
  33 struct ot200_backlight_data {
  34         int current_brightness;
  35 };
  36
  37 #define GPIO_DIMM       27
  38 #define SCALE           1
  39 #define CMP1MODE        0x2     /* compare on GE; output high on compare
  40                                  * greater than or equal */
  41 #define PWM_SETUP       (SCALE | CMP1MODE << 6 | MFGPT_SETUP_CNTEN)
  42 #define MAX_COMP2       163
  43
  44 static int ot200_backlight_update_status(struct backlight_device *bl)
  45 {
  46         struct ot200_backlight_data *data = bl_get_data(bl);
  47         int brightness = bl->props.brightness;
  48
  49         if (bl->props.state & BL_CORE_FBBLANK)
  50                 brightness = 0;
  51
  52         /* enable or disable PWM timer */
  53         if (brightness == 0)
  54                 cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, 0);
  55         else if (data->current_brightness == 0) {
  56                 cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
  57                 cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP,
  58                         MFGPT_SETUP_CNTEN);
  59         }
  60
  61         /* apply new brightness value */
  62         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
  63                 MAX_COMP2 - dim_table[brightness]);
  64         data->current_brightness = brightness;
  65
  66         return 0;
  67 }
  68
  69 static int ot200_backlight_get_brightness(struct backlight_device *bl)
  70 {
  71         struct ot200_backlight_data *data = bl_get_data(bl);
  72         return data->current_brightness;
  73 }
  74
  75 static const struct backlight_ops ot200_backlight_ops = {
  76         .update_status  = ot200_backlight_update_status,
  77         .get_brightness = ot200_backlight_get_brightness,
  78 };
  79
  80 static int ot200_backlight_probe(struct platform_device *pdev)
  81 {
  82         struct backlight_device *bl;
  83         struct ot200_backlight_data *data;
  84         struct backlight_properties props;
  85         int retval = 0;
  86
  87         /* request gpio */
  88         if (devm_gpio_request(&pdev->dev, GPIO_DIMM,
  89                                 "ot200 backlight dimmer") < 0) {
  90                 dev_err(&pdev->dev, "failed to request GPIO %d\n", GPIO_DIMM);
  91                 return -ENODEV;
  92         }
  93
  94         /* request timer */
  95         pwm_timer = cs5535_mfgpt_alloc_timer(7, MFGPT_DOMAIN_ANY);
  96         if (!pwm_timer) {
  97                 dev_err(&pdev->dev, "MFGPT 7 not available\n");
  98                 return -ENODEV;
  99         }
 100
 101         data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
 102         if (!data) {
 103                 retval = -ENOMEM;
 104                 goto error_devm_kzalloc;
 105         }
 106
 107         /* setup gpio */
 108         cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_ENABLE);
 109         cs5535_gpio_set(GPIO_DIMM, GPIO_OUTPUT_AUX1);
 110
 111         /* setup timer */
 112         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1, 0);
 113         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP2, MAX_COMP2);
 114         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, PWM_SETUP);
 115
 116         data->current_brightness = 100;
 117         props.max_brightness = 100;
 118         props.brightness = 100;
 119         props.type = BACKLIGHT_RAW;
 120
 121         bl = devm_backlight_device_register(&pdev->dev, dev_name(&pdev->dev),
 122                                         &pdev->dev, data, &ot200_backlight_ops,
 123                                         &props);
 124         if (IS_ERR(bl)) {
 125                 dev_err(&pdev->dev, "failed to register backlight\n");
 126                 retval = PTR_ERR(bl);
 127                 goto error_devm_kzalloc;
 128         }
 129
 130         platform_set_drvdata(pdev, bl);
 131
 132         return 0;
 133
 134 error_devm_kzalloc:
 135         cs5535_mfgpt_free_timer(pwm_timer);
 136         return retval;
 137 }
 138
 139 static int ot200_backlight_remove(struct platform_device *pdev)
 140 {
 141         /* on module unload set brightness to 100% */
 142         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_COUNTER, 0);
 143         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
 144         cs5535_mfgpt_write(pwm_timer, MFGPT_REG_CMP1,
 145                 MAX_COMP2 - dim_table[100]);
 146
 147         cs5535_mfgpt_free_timer(pwm_timer);
 148
 149         return 0;
 150 }
 151
 152 static struct platform_driver ot200_backlight_driver = {
 153         .driver         = {
 154                 .name   = "ot200-backlight",
 155                 .owner  = THIS_MODULE,
 156         },
 157         .probe          = ot200_backlight_probe,
 158         .remove         = ot200_backlight_remove,
 159 };
 160
 161 module_platform_driver(ot200_backlight_driver);
 162
 163 MODULE_DESCRIPTION("backlight driver for ot200 visualisation device");
 164 MODULE_AUTHOR("Christian Gmeiner <christian.gmeiner@gmail.com>");
 165 MODULE_LICENSE("GPL");
 166 MODULE_ALIAS("platform:ot200-backlight");