diff options
Diffstat (limited to 'target/linux/generic/files/drivers/pwm/gpio-pwm.c')
| -rw-r--r-- | target/linux/generic/files/drivers/pwm/gpio-pwm.c | 298 |
1 files changed, 298 insertions, 0 deletions
diff --git a/target/linux/generic/files/drivers/pwm/gpio-pwm.c b/target/linux/generic/files/drivers/pwm/gpio-pwm.c new file mode 100644 index 000000000..dff5d1d62 --- /dev/null +++ b/target/linux/generic/files/drivers/pwm/gpio-pwm.c @@ -0,0 +1,298 @@ +/* + * drivers/pwm/gpio.c + * + * Models a single-channel PWM device using a timer and a GPIO pin. + * + * Copyright (C) 2010 Bill Gatliff <bgat@billgatliff.com> + * + * This program is free software; you may redistribute and/or modify + * it under the terms of the GNU General Public License Version 2, as + * published by the Free Software Foundation. + * + * 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. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 + * USA + */ + +#include <linux/module.h> +#include <linux/init.h> +#include <linux/hrtimer.h> +#include <linux/err.h> +#include <linux/platform_device.h> +#include <linux/workqueue.h> +#include <linux/gpio.h> +#include <linux/slab.h> +#include <linux/pwm/pwm.h> + +struct gpio_pwm { + struct pwm_device pwm; + struct hrtimer timer; + struct work_struct work; + pwm_callback_t callback; + int gpio; + unsigned long polarity : 1; + unsigned long active : 1; +}; + +static inline struct gpio_pwm *to_gpio_pwm(const struct pwm_channel *p) +{ + return container_of(p->pwm, struct gpio_pwm, pwm); +} + +static void +gpio_pwm_work (struct work_struct *work) +{ + struct gpio_pwm *gp = container_of(work, struct gpio_pwm, work); + + if (gp->active) + gpio_direction_output(gp->gpio, gp->polarity ? 1 : 0); + else + gpio_direction_output(gp->gpio, gp->polarity ? 0 : 1); +} + +static enum hrtimer_restart +gpio_pwm_timeout(struct hrtimer *t) +{ + struct gpio_pwm *gp = container_of(t, struct gpio_pwm, timer); + ktime_t tnew; + + if (unlikely(gp->pwm.channels[0].duty_ticks == 0)) + gp->active = 0; + else if (unlikely(gp->pwm.channels[0].duty_ticks + == gp->pwm.channels[0].period_ticks)) + gp->active = 1; + else + gp->active ^= 1; + + if (gpio_cansleep(gp->gpio)) + schedule_work(&gp->work); + else + gpio_pwm_work(&gp->work); + + if (!gp->active && gp->pwm.channels[0].callback) + gp->pwm.channels[0].callback(&gp->pwm.channels[0]); + + if (unlikely(!gp->active && + (gp->pwm.channels[0].flags & BIT(FLAG_STOP)))) { + clear_bit(FLAG_STOP, &gp->pwm.channels[0].flags); + complete_all(&gp->pwm.channels[0].complete); + return HRTIMER_NORESTART; + } + + if (gp->active) + tnew = ktime_set(0, gp->pwm.channels[0].duty_ticks); + else + tnew = ktime_set(0, gp->pwm.channels[0].period_ticks + - gp->pwm.channels[0].duty_ticks); + hrtimer_start(&gp->timer, tnew, HRTIMER_MODE_REL); + + return HRTIMER_NORESTART; +} + +static void gpio_pwm_start(struct pwm_channel *p) +{ + struct gpio_pwm *gp = to_gpio_pwm(p); + + gp->active = 0; + gpio_pwm_timeout(&gp->timer); +} + +static int +gpio_pwm_config_nosleep(struct pwm_channel *p, + struct pwm_channel_config *c) +{ + struct gpio_pwm *gp = to_gpio_pwm(p); + int ret = 0; + unsigned long flags; + + spin_lock_irqsave(&p->lock, flags); + + switch (c->config_mask) { + + case PWM_CONFIG_DUTY_TICKS: + p->duty_ticks = c->duty_ticks; + break; + + case PWM_CONFIG_START: + if (!hrtimer_active(&gp->timer)) { + gpio_pwm_start(p); + } + break; + default: + ret = -EINVAL; + break; + } + + spin_unlock_irqrestore(&p->lock, flags); + return ret; +} + +static int +gpio_pwm_stop_sync(struct pwm_channel *p) +{ + struct gpio_pwm *gp = to_gpio_pwm(p); + int ret; + int was_on = hrtimer_active(&gp->timer); + + if (was_on) { + do { + init_completion(&p->complete); + set_bit(FLAG_STOP, &p->flags); + ret = wait_for_completion_interruptible(&p->complete); + if (ret) + return ret; + } while (p->flags & BIT(FLAG_STOP)); + } + + return was_on; +} + +static int +gpio_pwm_config(struct pwm_channel *p, + struct pwm_channel_config *c) +{ + struct gpio_pwm *gp = to_gpio_pwm(p); + int was_on = 0; + + if (p->pwm->config_nosleep) { + if (!p->pwm->config_nosleep(p, c)) + return 0; + } + + might_sleep(); + + was_on = gpio_pwm_stop_sync(p); + if (was_on < 0) + return was_on; + + if (c->config_mask & PWM_CONFIG_PERIOD_TICKS) + p->period_ticks = c->period_ticks; + + if (c->config_mask & PWM_CONFIG_DUTY_TICKS) + p->duty_ticks = c->duty_ticks; + + if (c->config_mask & PWM_CONFIG_POLARITY) { + gp->polarity = c->polarity ? 1 : 0; + p->active_high = gp->polarity; + } + + if ((c->config_mask & PWM_CONFIG_START) + || (was_on && !(c->config_mask & PWM_CONFIG_STOP))) + gpio_pwm_start(p); + + return 0; +} + +static int +gpio_pwm_set_callback(struct pwm_channel *p, + pwm_callback_t callback) +{ + struct gpio_pwm *gp = to_gpio_pwm(p); + gp->callback = callback; + return 0; +} + +static int +gpio_pwm_request(struct pwm_channel *p) +{ + p->tick_hz = 1000000000UL; + return 0; +} + +static int __devinit +gpio_pwm_probe(struct platform_device *pdev) +{ + struct gpio_pwm *gp; + struct gpio_pwm_platform_data *gpd = pdev->dev.platform_data; + int ret = 0; + + /* TODO: create configfs entries, so users can assign GPIOs to + * PWMs at runtime instead of creating a platform_device + * specification and rebuilding their kernel */ + + if (!gpd || gpio_request(gpd->gpio, dev_name(&pdev->dev))) + return -EINVAL; + + gp = kzalloc(sizeof(*gp), GFP_KERNEL); + if (!gp) { + ret = -ENOMEM; + goto err_alloc; + } + + platform_set_drvdata(pdev, gp); + + gp->pwm.dev = &pdev->dev; + gp->pwm.bus_id = dev_name(&pdev->dev); + gp->pwm.nchan = 1; + gp->gpio = gpd->gpio; + + INIT_WORK(&gp->work, gpio_pwm_work); + + hrtimer_init(&gp->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + gp->timer.function = gpio_pwm_timeout; + + gp->pwm.owner = THIS_MODULE; + gp->pwm.config_nosleep = gpio_pwm_config_nosleep; + gp->pwm.config = gpio_pwm_config; + gp->pwm.request = gpio_pwm_request; + gp->pwm.set_callback = gpio_pwm_set_callback; + + ret = pwm_register(&gp->pwm); + if (ret) + goto err_pwm_register; + + return 0; + +err_pwm_register: + platform_set_drvdata(pdev, 0); + kfree(gp); +err_alloc: + return ret; +} + +static int __devexit +gpio_pwm_remove(struct platform_device *pdev) +{ + struct gpio_pwm *gp = platform_get_drvdata(pdev); + int ret; + + ret = pwm_unregister(&gp->pwm); + hrtimer_cancel(&gp->timer); + cancel_work_sync(&gp->work); + platform_set_drvdata(pdev, 0); + kfree(gp); + + return 0; +} + +static struct platform_driver gpio_pwm_driver = { + .driver = { + .name = "gpio_pwm", + .owner = THIS_MODULE, + }, + .probe = gpio_pwm_probe, + .remove = __devexit_p(gpio_pwm_remove), +}; + +static int __init gpio_pwm_init(void) +{ + return platform_driver_register(&gpio_pwm_driver); +} +module_init(gpio_pwm_init); + +static void __exit gpio_pwm_exit(void) +{ + platform_driver_unregister(&gpio_pwm_driver); +} +module_exit(gpio_pwm_exit); + +MODULE_AUTHOR("Bill Gatliff <bgat@billgatliff.com>"); +MODULE_DESCRIPTION("PWM output using GPIO and a high-resolution timer"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:gpio_pwm"); |