drivers/video/backlight/atmel-pwm-bl.c

   1 /*
   2  * Copyright (C) 2008 Atmel Corporation
   3  *
   4  * Backlight driver using Atmel PWM peripheral.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 as published by
   8  * the Free Software Foundation.
   9  */
  10 #include <linux/init.h>
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/fb.h>
  15 #include <linux/gpio.h>
  16 #include <linux/backlight.h>
  17 #include <linux/atmel_pwm.h>
  18 #include <linux/atmel-pwm-bl.h>
  19 #include <linux/slab.h>
  20
  21 struct atmel_pwm_bl {
  22         const struct atmel_pwm_bl_platform_data *pdata;
  23         struct backlight_device                 *bldev;
  24         struct platform_device                  *pdev;
  25         struct pwm_channel                      pwmc;
  26         int                                     gpio_on;
  27 };
  28
  29 static void atmel_pwm_bl_set_gpio_on(struct atmel_pwm_bl *pwmbl, int on)
  30 {
  31         if (!gpio_is_valid(pwmbl->gpio_on))
  32                 return;
  33
  34         gpio_set_value(pwmbl->gpio_on, on ^ pwmbl->pdata->on_active_low);
  35 }
  36
  37 static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
  38 {
  39         struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
  40         int intensity = bd->props.brightness;
  41         int pwm_duty;
  42
  43         if (bd->props.power != FB_BLANK_UNBLANK)
  44                 intensity = 0;
  45         if (bd->props.fb_blank != FB_BLANK_UNBLANK)
  46                 intensity = 0;
  47
  48         if (pwmbl->pdata->pwm_active_low)
  49                 pwm_duty = pwmbl->pdata->pwm_duty_min + intensity;
  50         else
  51                 pwm_duty = pwmbl->pdata->pwm_duty_max - intensity;
  52
  53         if (pwm_duty > pwmbl->pdata->pwm_duty_max)
  54                 pwm_duty = pwmbl->pdata->pwm_duty_max;
  55         if (pwm_duty < pwmbl->pdata->pwm_duty_min)
  56                 pwm_duty = pwmbl->pdata->pwm_duty_min;
  57
  58         if (!intensity) {
  59                 atmel_pwm_bl_set_gpio_on(pwmbl, 0);
  60                 pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
  61                 pwm_channel_disable(&pwmbl->pwmc);
  62         } else {
  63                 pwm_channel_enable(&pwmbl->pwmc);
  64                 pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
  65                 atmel_pwm_bl_set_gpio_on(pwmbl, 1);
  66         }
  67
  68         return 0;
  69 }
  70
  71 static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
  72 {
  73         struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
  74         u32 cdty;
  75         u32 intensity;
  76
  77         cdty = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
  78         if (pwmbl->pdata->pwm_active_low)
  79                 intensity = cdty - pwmbl->pdata->pwm_duty_min;
  80         else
  81                 intensity = pwmbl->pdata->pwm_duty_max - cdty;
  82
  83         return intensity & 0xffff;
  84 }
  85
  86 static int atmel_pwm_bl_init_pwm(struct atmel_pwm_bl *pwmbl)
  87 {
  88         unsigned long pwm_rate = pwmbl->pwmc.mck;
  89         unsigned long prescale = DIV_ROUND_UP(pwm_rate,
  90                         (pwmbl->pdata->pwm_frequency *
  91                          pwmbl->pdata->pwm_compare_max)) - 1;
  92
  93         /*
  94          * Prescale must be power of two and maximum 0xf in size because of
  95          * hardware limit. PWM speed will be:
  96          *      PWM module clock speed / (2 ^ prescale).
  97          */
  98         prescale = fls(prescale);
  99         if (prescale > 0xf)
 100                 prescale = 0xf;
 101
 102         pwm_channel_writel(&pwmbl->pwmc, PWM_CMR, prescale);
 103         pwm_channel_writel(&pwmbl->pwmc, PWM_CDTY,
 104                         pwmbl->pdata->pwm_duty_min +
 105                         pwmbl->bldev->props.brightness);
 106         pwm_channel_writel(&pwmbl->pwmc, PWM_CPRD,
 107                         pwmbl->pdata->pwm_compare_max);
 108
 109         dev_info(&pwmbl->pdev->dev, "Atmel PWM backlight driver (%lu Hz)\n",
 110                 pwmbl->pwmc.mck / pwmbl->pdata->pwm_compare_max /
 111                 (1 << prescale));
 112
 113         return pwm_channel_enable(&pwmbl->pwmc);
 114 }
 115
 116 static const struct backlight_ops atmel_pwm_bl_ops = {
 117         .get_brightness = atmel_pwm_bl_get_intensity,
 118         .update_status  = atmel_pwm_bl_set_intensity,
 119 };
 120
 121 static int atmel_pwm_bl_probe(struct platform_device *pdev)
 122 {
 123         struct backlight_properties props;
 124         const struct atmel_pwm_bl_platform_data *pdata;
 125         struct backlight_device *bldev;
 126         struct atmel_pwm_bl *pwmbl;
 127         unsigned long flags;
 128         int retval;
 129
 130         pdata = dev_get_platdata(&pdev->dev);
 131         if (!pdata)
 132                 return -ENODEV;
 133
 134         if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
 135                         pdata->pwm_duty_min > pdata->pwm_duty_max ||
 136                         pdata->pwm_frequency == 0)
 137                 return -EINVAL;
 138
 139         pwmbl = devm_kzalloc(&pdev->dev, sizeof(struct atmel_pwm_bl),
 140                                 GFP_KERNEL);
 141         if (!pwmbl)
 142                 return -ENOMEM;
 143
 144         pwmbl->pdev = pdev;
 145         pwmbl->pdata = pdata;
 146         pwmbl->gpio_on = pdata->gpio_on;
 147
 148         retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
 149         if (retval)
 150                 return retval;
 151
 152         if (gpio_is_valid(pwmbl->gpio_on)) {
 153                 /* Turn display off by default. */
 154                 if (pdata->on_active_low)
 155                         flags = GPIOF_OUT_INIT_HIGH;
 156                 else
 157                         flags = GPIOF_OUT_INIT_LOW;
 158
 159                 retval = devm_gpio_request_one(&pdev->dev, pwmbl->gpio_on,
 160                                                 flags, "gpio_atmel_pwm_bl");
 161                 if (retval)
 162                         goto err_free_pwm;
 163         }
 164
 165         memset(&props, 0, sizeof(struct backlight_properties));
 166         props.type = BACKLIGHT_RAW;
 167         props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
 168         bldev = devm_backlight_device_register(&pdev->dev, "atmel-pwm-bl",
 169                                         &pdev->dev, pwmbl, &atmel_pwm_bl_ops,
 170                                         &props);
 171         if (IS_ERR(bldev)) {
 172                 retval = PTR_ERR(bldev);
 173                 goto err_free_pwm;
 174         }
 175
 176         pwmbl->bldev = bldev;
 177
 178         platform_set_drvdata(pdev, pwmbl);
 179
 180         /* Power up the backlight by default at middle intesity. */
 181         bldev->props.power = FB_BLANK_UNBLANK;
 182         bldev->props.brightness = bldev->props.max_brightness / 2;
 183
 184         retval = atmel_pwm_bl_init_pwm(pwmbl);
 185         if (retval)
 186                 goto err_free_pwm;
 187
 188         atmel_pwm_bl_set_intensity(bldev);
 189
 190         return 0;
 191
 192 err_free_pwm:
 193         pwm_channel_free(&pwmbl->pwmc);
 194
 195         return retval;
 196 }
 197
 198 static int atmel_pwm_bl_remove(struct platform_device *pdev)
 199 {
 200         struct atmel_pwm_bl *pwmbl = platform_get_drvdata(pdev);
 201
 202         atmel_pwm_bl_set_gpio_on(pwmbl, 0);
 203         pwm_channel_disable(&pwmbl->pwmc);
 204         pwm_channel_free(&pwmbl->pwmc);
 205
 206         return 0;
 207 }
 208
 209 static struct platform_driver atmel_pwm_bl_driver = {
 210         .driver = {
 211                 .name = "atmel-pwm-bl",
 212         },
 213         /* REVISIT add suspend() and resume() */
 214         .probe = atmel_pwm_bl_probe,
 215         .remove = atmel_pwm_bl_remove,
 216 };
 217
 218 module_platform_driver(atmel_pwm_bl_driver);
 219
 220 MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
 221 MODULE_DESCRIPTION("Atmel PWM backlight driver");
 222 MODULE_LICENSE("GPL");
 223 MODULE_ALIAS("platform:atmel-pwm-bl");