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 #include <linux/slab.h>
  21
  22 struct atmel_pwm_bl {
  23         const struct atmel_pwm_bl_platform_data *pdata;
  24         struct backlight_device                 *bldev;
  25         struct platform_device                  *pdev;
  26         struct pwm_channel                      pwmc;
  27         int                                     gpio_on;
  28 };
  29
  30 static int atmel_pwm_bl_set_intensity(struct backlight_device *bd)
  31 {
  32         struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
  33         int intensity = bd->props.brightness;
  34         int pwm_duty;
  35
  36         if (bd->props.power != FB_BLANK_UNBLANK)
  37                 intensity = 0;
  38         if (bd->props.fb_blank != FB_BLANK_UNBLANK)
  39                 intensity = 0;
  40
  41         if (pwmbl->pdata->pwm_active_low)
  42                 pwm_duty = pwmbl->pdata->pwm_duty_min + intensity;
  43         else
  44                 pwm_duty = pwmbl->pdata->pwm_duty_max - intensity;
  45
  46         if (pwm_duty > pwmbl->pdata->pwm_duty_max)
  47                 pwm_duty = pwmbl->pdata->pwm_duty_max;
  48         if (pwm_duty < pwmbl->pdata->pwm_duty_min)
  49                 pwm_duty = pwmbl->pdata->pwm_duty_min;
  50
  51         if (!intensity) {
  52                 if (pwmbl->gpio_on != -1) {
  53                         gpio_set_value(pwmbl->gpio_on,
  54                                         0 ^ pwmbl->pdata->on_active_low);
  55                 }
  56                 pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
  57                 pwm_channel_disable(&pwmbl->pwmc);
  58         } else {
  59                 pwm_channel_enable(&pwmbl->pwmc);
  60                 pwm_channel_writel(&pwmbl->pwmc, PWM_CUPD, pwm_duty);
  61                 if (pwmbl->gpio_on != -1) {
  62                         gpio_set_value(pwmbl->gpio_on,
  63                                         1 ^ pwmbl->pdata->on_active_low);
  64                 }
  65         }
  66
  67         return 0;
  68 }
  69
  70 static int atmel_pwm_bl_get_intensity(struct backlight_device *bd)
  71 {
  72         struct atmel_pwm_bl *pwmbl = bl_get_data(bd);
  73         u8 intensity;
  74
  75         if (pwmbl->pdata->pwm_active_low) {
  76                 intensity = pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY) -
  77                         pwmbl->pdata->pwm_duty_min;
  78         } else {
  79                 intensity = pwmbl->pdata->pwm_duty_max -
  80                         pwm_channel_readl(&pwmbl->pwmc, PWM_CDTY);
  81         }
  82
  83         return intensity;
  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 __init 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 = devm_kzalloc(&pdev->dev, sizeof(struct atmel_pwm_bl),
 130                                 GFP_KERNEL);
 131         if (!pwmbl)
 132                 return -ENOMEM;
 133
 134         pwmbl->pdev = pdev;
 135
 136         pdata = pdev->dev.platform_data;
 137         if (!pdata) {
 138                 retval = -ENODEV;
 139                 goto err_free_mem;
 140         }
 141
 142         if (pdata->pwm_compare_max < pdata->pwm_duty_max ||
 143                         pdata->pwm_duty_min > pdata->pwm_duty_max ||
 144                         pdata->pwm_frequency == 0) {
 145                 retval = -EINVAL;
 146                 goto err_free_mem;
 147         }
 148
 149         pwmbl->pdata = pdata;
 150         pwmbl->gpio_on = pdata->gpio_on;
 151
 152         retval = pwm_channel_alloc(pdata->pwm_channel, &pwmbl->pwmc);
 153         if (retval)
 154                 goto err_free_mem;
 155
 156         if (pwmbl->gpio_on != -1) {
 157                 retval = devm_gpio_request(&pdev->dev, pwmbl->gpio_on,
 158                                         "gpio_atmel_pwm_bl");
 159                 if (retval) {
 160                         pwmbl->gpio_on = -1;
 161                         goto err_free_pwm;
 162                 }
 163
 164                 /* Turn display off by default. */
 165                 retval = gpio_direction_output(pwmbl->gpio_on,
 166                                 0 ^ pdata->on_active_low);
 167                 if (retval)
 168                         goto err_free_pwm;
 169         }
 170
 171         memset(&props, 0, sizeof(struct backlight_properties));
 172         props.type = BACKLIGHT_RAW;
 173         props.max_brightness = pdata->pwm_duty_max - pdata->pwm_duty_min;
 174         bldev = backlight_device_register("atmel-pwm-bl", &pdev->dev, pwmbl,
 175                                           &atmel_pwm_bl_ops, &props);
 176         if (IS_ERR(bldev)) {
 177                 retval = PTR_ERR(bldev);
 178                 goto err_free_pwm;
 179         }
 180
 181         pwmbl->bldev = bldev;
 182
 183         platform_set_drvdata(pdev, pwmbl);
 184
 185         /* Power up the backlight by default at middle intesity. */
 186         bldev->props.power = FB_BLANK_UNBLANK;
 187         bldev->props.brightness = bldev->props.max_brightness / 2;
 188
 189         retval = atmel_pwm_bl_init_pwm(pwmbl);
 190         if (retval)
 191                 goto err_free_bl_dev;
 192
 193         atmel_pwm_bl_set_intensity(bldev);
 194
 195         return 0;
 196
 197 err_free_bl_dev:
 198         backlight_device_unregister(bldev);
 199 err_free_pwm:
 200         pwm_channel_free(&pwmbl->pwmc);
 201 err_free_mem:
 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         pwm_channel_disable(&pwmbl->pwmc);
 212         pwm_channel_free(&pwmbl->pwmc);
 213         backlight_device_unregister(pwmbl->bldev);
 214
 215         return 0;
 216 }
 217
 218 static struct platform_driver atmel_pwm_bl_driver = {
 219         .driver = {
 220                 .name = "atmel-pwm-bl",
 221         },
 222         /* REVISIT add suspend() and resume() */
 223         .remove = __exit_p(atmel_pwm_bl_remove),
 224 };
 225
 226 module_platform_driver_probe(atmel_pwm_bl_driver, atmel_pwm_bl_probe);
 227
 228 MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
 229 MODULE_DESCRIPTION("Atmel PWM backlight driver");
 230 MODULE_LICENSE("GPL");