tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
21struct 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
29static 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
69static 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
85static 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
116static 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
121static 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 defatult. */
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
192err_free_bl_dev:
193 platform_set_drvdata(pdev, NULL);
194 backlight_device_unregister(bldev);
195err_free_gpio:
196 if (pwmbl->gpio_on != -1)
197 gpio_free(pwmbl->gpio_on);
198err_free_pwm:
199 pwm_channel_free(&pwmbl->pwmc);
200err_free_mem:
201 kfree(pwmbl);
202 return retval;
203}
204
205static 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
222static 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
230static int __init atmel_pwm_bl_init(void)
231{
232 return platform_driver_probe(&atmel_pwm_bl_driver, atmel_pwm_bl_probe);
233}
234module_init(atmel_pwm_bl_init);
235
236static void __exit atmel_pwm_bl_exit(void)
237{
238 platform_driver_unregister(&atmel_pwm_bl_driver);
239}
240module_exit(atmel_pwm_bl_exit);
241
242MODULE_AUTHOR("Hans-Christian egtvedt <hans-christian.egtvedt@atmel.com>");
243MODULE_DESCRIPTION("Atmel PWM backlight driver");
244MODULE_LICENSE("GPL");