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         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         int retval;
 128
 129         pwmbl = kzalloc(sizeof(struct atmel_pwm_bl), GFP_KERNEL);
 130         if (!pwmbl)
 131                 return -ENOMEM;
 132
 133         pwmbl->pdev = pdev;
 134
 135         pdata = pdev->dev.platform_data;
 136         if (!pdata) {
 137                 retval = -ENODEV;
 138                 goto err_free_mem;
 139         }
 140
 141         if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
 142                         pdata->pwm_duty_min > pdata->pwm_duty_max ||
 143                         pdata->pwm_frequency == 0) {
 144                 retval = -EINVAL;
 145                 goto err_free_mem;
 146         }
 147
 148         pwmbl->pdata = pdata;
 149         pwmbl->gpio_on = pdata->gpio_on;
 150
 151         retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
 152         if (retval)
 153                 goto err_free_mem;
 154
 155         if (pwmbl->gpio_on != -1) {
 156                 retval = gpio_request(pwmbl->gpio_on, "gpio_atmel_pwm_bl");
 157                 if (retval) {
 158                         pwmbl->gpio_on = -1;
 159                         goto err_free_pwm;
 160                 }
 161
 162                 /* Turn display off by default. */
 163                 retval = gpio_direction_output(pwmbl->gpio_on,
 164                                 0 ^ pdata->on_active_low);
 165                 if (retval)
 166                         goto err_free_gpio;
 167         }
 168
 169         memset(&props, 0, sizeof(struct backlight_properties));
 170         props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
 171         bldev = backlight_device_register("atmel-pwm-bl", &pdev->dev, pwmbl,
 172                                           &atmel_pwm_bl_ops, &props);
 173         if (IS_ERR(bldev)) {
 174                 retval = PTR_ERR(bldev);
 175                 goto err_free_gpio;
 176         }
 177
 178         pwmbl->bldev = bldev;
 179
 180         platform_set_drvdata(pdev, pwmbl);
 181
 182         /* Power up the backlight by default at middle intesity. */
 183         bldev->props.power = FB_BLANK_UNBLANK;
 184         bldev->props.brightness = bldev->props.max_brightness / 2;
 185
 186         retval = atmel_pwm_bl_init_pwm(pwmbl);
 187         if (retval)
 188                 goto err_free_bl_dev;
 189
 190         atmel_pwm_bl_set_intensity(bldev);
 191
 192         return 0;
 193
 194 err_free_bl_dev:
 195         platform_set_drvdata(pdev, NULL);
 196         backlight_device_unregister(bldev);
 197 err_free_gpio:
 198         if (pwmbl->gpio_on != -1)
 199                 gpio_free(pwmbl->gpio_on);
 200 err_free_pwm:
 201         pwm_channel_free(&pwmbl->pwmc);
 202 err_free_mem:
 203         kfree(pwmbl);
 204         return retval;
 205 }
 206
 207 static int __exit atmel_pwm_bl_remove(struct platform_device *pdev)
 208 {
 209         struct atmel_pwm_bl *pwmbl = platform_get_drvdata(pdev);
 210
 211         if (pwmbl->gpio_on != -1) {
 212                 gpio_set_value(pwmbl->gpio_on, 0);
 213                 gpio_free(pwmbl->gpio_on);
 214         }
 215         pwm_channel_disable(&pwmbl->pwmc);
 216         pwm_channel_free(&pwmbl->pwmc);
 217         backlight_device_unregister(pwmbl->bldev);
 218         platform_set_drvdata(pdev, NULL);
 219         kfree(pwmbl);
 220
 221         return 0;
 222 }
 223
 224 static struct platform_driver atmel_pwm_bl_driver = {
 225         .driver = {
 226                 .name = "atmel-pwm-bl",
 227         },
 228         /* REVISIT add suspend() and resume() */
 229         .remove = __exit_p(atmel_pwm_bl_remove),
 230 };
 231
 232 static int __init atmel_pwm_bl_init(void)
 233 {
 234         return platform_driver_probe(&atmel_pwm_bl_driver, atmel_pwm_bl_probe);
 235 }
 236 module_init(atmel_pwm_bl_init);
 237
 238 static void __exit atmel_pwm_bl_exit(void)
 239 {
 240         platform_driver_unregister(&atmel_pwm_bl_driver);
 241 }
 242 module_exit(atmel_pwm_bl_exit);
 243
 244 MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
 245 MODULE_DESCRIPTION("Atmel PWM backlight driver");
 246 MODULE_LICENSE("GPL");