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/clk.h>
  16 #include <linux/gpio.h>
  17 #include <linux/backlight.h>
  18 #include <linux/atmel_pwm.h>
  19 #include <linux/atmel-pwm-bl.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 int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
  30 {
  31         struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
  32         int intensity = bd->props.brightness;
  33         int pwm_duty;
  34
  35         if (bd->props.power != FB_BLANK_UNBLANK)
  36                 intensity = 0;
  37         if (bd->props.fb_blank != FB_BLANK_UNBLANK)
  38                 intensity = 0;
  39
  40         if (pwmbl->pdata->pwm_active_low)
  41                 pwm_duty = pwmbl->pdata->pwm_duty_min + intensity;
  42         else
  43                 pwm_duty = pwmbl->pdata->pwm_duty_max - intensity;
  44
  45         if (pwm_duty > pwmbl->pdata->pwm_duty_max)
  46                 pwm_duty = pwmbl->pdata->pwm_duty_max;
  47         if (pwm_duty < pwmbl->pdata->pwm_duty_min)
  48                 pwm_duty = pwmbl->pdata->pwm_duty_min;
  49
  50         if (!intensity) {
  51                 if (pwmbl->gpio_on != -1) {
  52                         gpio_set_value(pwmbl->gpio_on,
  53                                         0 ^ pwmbl->pdata->on_active_low);
  54                 }
  55                 pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
  56                 pwm_channel_disable(&pwmbl->pwmc);
  57         } else {
  58                 pwm_channel_enable(&pwmbl->pwmc);
  59                 pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
  60                 if (pwmbl->gpio_on != -1) {
  61                         gpio_set_value(pwmbl->gpio_on,
  62                                         1 ^ pwmbl->pdata->on_active_low);
  63                 }
  64         }
  65
  66         return 0;
  67 }
  68
  69 static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
  70 {
  71         struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
  72         u8 intensity;
  73
  74         if (pwmbl->pdata->pwm_active_low) {
  75                 intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
  76                         pwmbl->pdata->pwm_duty_min;
  77         } else {
  78                 intensity = pwmbl->pdata->pwm_duty_max -
  79                         pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
  80         }
  81
  82         return intensity;
  83 }
  84
  85 static int atmel_pwm_bl_init_pwm(struct atmel_pwm_bl *pwmbl)
  86 {
  87         unsigned long pwm_rate = pwmbl->pwmc.mck;
  88         unsigned long prescale = DIV_ROUND_UP(pwm_rate,
  89                         (pwmbl->pdata->pwm_frequency *
  90                          pwmbl->pdata->pwm_compare_max)) - 1;
  91
  92         /*
  93          * Prescale must be power of two and maximum 0xf in size because of
  94          * hardware limit. PWM speed will be:
  95          *      PWM module clock speed / (2 ^ prescale).
  96          */
  97         prescale = fls(prescale);
  98         if (prescale > 0xf)
  99                 prescale = 0xf;
 100
 101         pwm_channel_writel(&pwmbl->pwmc, PWM_CMR, prescale);
 102         pwm_channel_writel(&pwmbl->pwmc, PWM_CDTY,
 103                         pwmbl->pdata->pwm_duty_min +
 104                         pwmbl->bldev->props.brightness);
 105         pwm_channel_writel(&pwmbl->pwmc, PWM_CPRD,
 106                         pwmbl->pdata->pwm_compare_max);
 107
 108         dev_info(&pwmbl->pdev->dev, "Atmel PWM backlight driver "
 109                         "(%lu Hz)\n", pwmbl->pwmc.mck /
 110                         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         const struct atmel_pwm_bl_platform_data *pdata;
 124         struct backlight_device *bldev;
 125         struct atmel_pwm_bl *pwmbl;
 126         int retval;
 127
 128         pwmbl = kzalloc(sizeof(struct atmel_pwm_bl), GFP_KERNEL);
 129         if (!pwmbl)
 130                 return -ENOMEM;
 131
 132         pwmbl->pdev = pdev;
 133
 134         pdata = pdev->dev.platform_data;
 135         if (!pdata) {
 136                 retval = -ENODEV;
 137                 goto err_free_mem;
 138         }
 139
 140         if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
 141                         pdata->pwm_duty_min > pdata->pwm_duty_max ||
 142                         pdata->pwm_frequency == 0) {
 143                 retval = -EINVAL;
 144                 goto err_free_mem;
 145         }
 146
 147         pwmbl->pdata = pdata;
 148         pwmbl->gpio_on = pdata->gpio_on;
 149
 150         retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
 151         if (retval)
 152                 goto err_free_mem;
 153
 154         if (pwmbl->gpio_on != -1) {
 155                 retval = gpio_request(pwmbl->gpio_on, "gpio_atmel_pwm_bl");
 156                 if (retval) {
 157                         pwmbl->gpio_on = -1;
 158                         goto err_free_pwm;
 159                 }
 160
 161                 /* Turn display off by default. */
 162                 retval = gpio_direction_output(pwmbl->gpio_on,
 163                                 0 ^ pdata->on_active_low);
 164                 if (retval)
 165                         goto err_free_gpio;
 166         }
 167
 168         bldev = backlight_device_register("atmel-pwm-bl",
 169                         &pdev->dev, pwmbl, &atmel_pwm_bl_ops);
 170         if (IS_ERR(bldev)) {
 171                 retval = PTR_ERR(bldev);
 172                 goto err_free_gpio;
 173         }
 174
 175         pwmbl->bldev = bldev;
 176
 177         platform_set_drvdata(pdev, pwmbl);
 178
 179         /* Power up the backlight by default at middle intesity. */
 180         bldev->props.power = FB_BLANK_UNBLANK;
 181         bldev->props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
 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_bl_dev;
 187
 188         atmel_pwm_bl_set_intensity(bldev);
 189
 190         return 0;
 191
 192 err_free_bl_dev:
 193         platform_set_drvdata(pdev, NULL);
 194         backlight_device_unregister(bldev);
 195 err_free_gpio:
 196         if (pwmbl->gpio_on != -1)
 197                 gpio_free(pwmbl->gpio_on);
 198 err_free_pwm:
 199         pwm_channel_free(&pwmbl->pwmc);
 200 err_free_mem:
 201         kfree(pwmbl);
 202         return retval;
 203 }
 204
 205 static int __exit atmel_pwm_bl_remove(struct platform_device *pdev)
 206 {
 207         struct atmel_pwm_bl *pwmbl = platform_get_drvdata(pdev);
 208
 209         if (pwmbl->gpio_on != -1) {
 210                 gpio_set_value(pwmbl->gpio_on, 0);
 211                 gpio_free(pwmbl->gpio_on);
 212         }
 213         pwm_channel_disable(&pwmbl->pwmc);
 214         pwm_channel_free(&pwmbl->pwmc);
 215         backlight_device_unregister(pwmbl->bldev);
 216         platform_set_drvdata(pdev, NULL);
 217         kfree(pwmbl);
 218
 219         return 0;
 220 }
 221
 222 static struct platform_driver atmel_pwm_bl_driver = {
 223         .driver = {
 224                 .name = "atmel-pwm-bl",
 225         },
 226         /* REVISIT add suspend() and resume() */
 227         .remove = __exit_p(atmel_pwm_bl_remove),
 228 };
 229
 230 static int __init atmel_pwm_bl_init(void)
 231 {
 232         return platform_driver_probe(&atmel_pwm_bl_driver, atmel_pwm_bl_probe);
 233 }
 234 module_init(atmel_pwm_bl_init);
 235
 236 static void __exit atmel_pwm_bl_exit(void)
 237 {
 238         platform_driver_unregister(&atmel_pwm_bl_driver);
 239 }
 240 module_exit(atmel_pwm_bl_exit);
 241
 242 MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
 243 MODULE_DESCRIPTION("Atmel PWM backlight driver");
 244 MODULE_LICENSE("GPL");