diff options
Diffstat (limited to 'drivers/video/backlight-pwm.c')
| -rw-r--r-- | drivers/video/backlight-pwm.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/drivers/video/backlight-pwm.c b/drivers/video/backlight-pwm.c new file mode 100644 index 0000000000..91b148109b --- /dev/null +++ b/drivers/video/backlight-pwm.c @@ -0,0 +1,199 @@ +/* + * pwm backlight support for barebox + * + * (C) Copyright 2014 Sascha Hauer, Pengutronix + * + * See file CREDITS for list of people who contributed to this + * project. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of + * the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + */ +#include <common.h> +#include <malloc.h> +#include <init.h> +#include <video/backlight.h> +#include <pwm.h> +#include <linux/err.h> +#include <of.h> +#include <gpio.h> +#include <of_gpio.h> +#include <asm-generic/div64.h> + +struct pwm_backlight { + struct backlight_device backlight; + struct pwm_device *pwm; + uint32_t period; + unsigned int *levels; + int enable_gpio; + int enable_active_high; + int max_value; + int enabled; +}; + +static int backlight_pwm_enable(struct pwm_backlight *pwm_backlight) +{ + int ret; + + if (pwm_backlight->enabled) + return 0; + + ret = pwm_enable(pwm_backlight->pwm); + if (ret) + return ret; + + if (gpio_is_valid(pwm_backlight->enable_gpio)) { + gpio_direction_output(pwm_backlight->enable_gpio, + pwm_backlight->enable_active_high); + } + + pwm_backlight->enabled = 1; + + return 0; +} + +static int backlight_pwm_disable(struct pwm_backlight *pwm_backlight) +{ + if (!pwm_backlight->enabled) + return 0; + + if (gpio_is_valid(pwm_backlight->enable_gpio)) { + gpio_direction_output(pwm_backlight->enable_gpio, + !pwm_backlight->enable_active_high); + /* + * Only disable PWM when an enable gpio is present. + * The output of the PWM is undefined when the PWM + * is disabled. + */ + pwm_disable(pwm_backlight->pwm); + pwm_backlight->enabled = 0; + } + + return 0; +} + +static int backlight_pwm_set(struct backlight_device *backlight, + int brightness) +{ + struct pwm_backlight *pwm_backlight = container_of(backlight, + struct pwm_backlight, backlight); + unsigned long long duty = pwm_backlight->period; + unsigned int max = pwm_backlight->backlight.brightness_max; + + duty *= brightness; + do_div(duty, max); + + pwm_config(pwm_backlight->pwm, duty, pwm_backlight->period); + + if (brightness) + return backlight_pwm_enable(pwm_backlight); + else + return backlight_pwm_disable(pwm_backlight); +} + +static int pwm_backlight_parse_dt(struct device_d *dev, + struct pwm_backlight *pwm_backlight) +{ + struct device_node *node = dev->device_node; + struct property *prop; + int length; + u32 value; + int ret; + enum of_gpio_flags flags; + + if (!node) + return -ENODEV; + + /* determine the number of brightness levels */ + prop = of_find_property(node, "brightness-levels", &length); + if (!prop) + return -EINVAL; + + pwm_backlight->backlight.brightness_max = length / sizeof(u32); + + /* read brightness levels from DT property */ + if (pwm_backlight->backlight.brightness_max > 0) { + size_t size = sizeof(*pwm_backlight->levels) * + pwm_backlight->backlight.brightness_max; + + pwm_backlight->levels = xzalloc(size); + if (!pwm_backlight->levels) + return -ENOMEM; + + ret = of_property_read_u32_array(node, "brightness-levels", + pwm_backlight->levels, + pwm_backlight->backlight.brightness_max); + if (ret < 0) + return ret; + + ret = of_property_read_u32(node, "default-brightness-level", + &value); + if (ret < 0) + return ret; + + pwm_backlight->backlight.brightness_default = value; + pwm_backlight->backlight.brightness_max--; + } + + pwm_backlight->enable_gpio = of_get_named_gpio_flags(node, "enable-gpios", 0, &flags); + + if (gpio_is_valid(pwm_backlight->enable_gpio)) { + if (!(flags & OF_GPIO_ACTIVE_LOW)) + pwm_backlight->enable_active_high = 1; + } + + return 0; +} + +static int backlight_pwm_of_probe(struct device_d *dev) +{ + int ret; + struct pwm_backlight *pwm_backlight; + struct pwm_device *pwm; + + pwm = of_pwm_request(dev->device_node, NULL); + if (IS_ERR(pwm)) + return PTR_ERR(pwm); + + pwm_backlight = xzalloc(sizeof(*pwm_backlight)); + pwm_backlight->pwm = pwm; + pwm_backlight->period = pwm_get_period(pwm); + + ret = pwm_backlight_parse_dt(dev, pwm_backlight); + if (ret) + return ret; + + pwm_backlight->period = pwm_get_period(pwm_backlight->pwm); + + pwm_backlight->backlight.brightness_set = backlight_pwm_set; + pwm_backlight->backlight.node = dev->device_node; + + ret = backlight_register(&pwm_backlight->backlight); + if (ret) + return ret; + + return 0; +} + +static struct of_device_id backlight_pwm_of_ids[] = { + { + .compatible = "pwm-backlight", + }, { + /* sentinel */ + } +}; + +static struct driver_d backlight_pwm_of_driver = { + .name = "pwm-backlight", + .probe = backlight_pwm_of_probe, + .of_compatible = DRV_OF_COMPAT(backlight_pwm_of_ids), +}; +device_platform_driver(backlight_pwm_of_driver); |