/*
 * STMicroelectronics sensors trigger library driver
 *
 * Copyright 2012-2013 STMicroelectronics Inc.
 *
 * Denis Ciocca <denis.ciocca@st.com>
 *
 * Licensed under the GPL-2.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/iio/iio.h>
#include <linux/iio/trigger.h>
#include <linux/interrupt.h>
#include <linux/iio/common/st_sensors.h>
#include "st_sensors_core.h"

/**
 * st_sensors_new_samples_available() - check if more samples came in
 * returns:
 * 0 - no new samples available
 * 1 - new samples available
 * negative - error or unknown
 */
static int st_sensors_new_samples_available(struct iio_dev *indio_dev,
                                            struct st_sensor_data *sdata)
{
        u8 status;
        int ret;

        /* How would I know if I can't check it? */
        if (!sdata->sensor_settings->drdy_irq.stat_drdy.addr)
                return -EINVAL;

        /* No scan mask, no interrupt */
        if (!indio_dev->active_scan_mask)
                return 0;

        ret = sdata->tf->read_byte(&sdata->tb, sdata->dev,
                        sdata->sensor_settings->drdy_irq.stat_drdy.addr,
                        &status);
        if (ret < 0) {
                dev_err(sdata->dev,
                        "error checking samples available\n");
                return ret;
        }

        if (status & sdata->sensor_settings->drdy_irq.stat_drdy.mask)
                return 1;

        return 0;
}

/**
 * st_sensors_irq_handler() - top half of the IRQ-based triggers
 * @irq: irq number
 * @p: private handler data
 */
static irqreturn_t st_sensors_irq_handler(int irq, void *p)
{
        struct iio_trigger *trig = p;
        struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        struct st_sensor_data *sdata = iio_priv(indio_dev);

        /* Get the time stamp as close in time as possible */
        sdata->hw_timestamp = iio_get_time_ns(indio_dev);
        return IRQ_WAKE_THREAD;
}

/**
 * st_sensors_irq_thread() - bottom half of the IRQ-based triggers
 * @irq: irq number
 * @p: private handler data
 */
static irqreturn_t st_sensors_irq_thread(int irq, void *p)
{
        struct iio_trigger *trig = p;
        struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
        struct st_sensor_data *sdata = iio_priv(indio_dev);

        /*
         * If this trigger is backed by a hardware interrupt and we have a
         * status register, check if this IRQ came from us. Notice that
         * we will process also if st_sensors_new_samples_available()
         * returns negative: if we can't check status, then poll
         * unconditionally.
         */
        if (sdata->hw_irq_trigger &&
            st_sensors_new_samples_available(indio_dev, sdata)) {
                iio_trigger_poll_chained(p);
        } else {
                dev_dbg(sdata->dev, "spurious IRQ\n");
                return IRQ_NONE;
        }

        /*
         * If we have proper level IRQs the handler will be re-entered if
         * the line is still active, so return here and come back in through
         * the top half if need be.
         */
        if (!sdata->edge_irq)
                return IRQ_HANDLED;

        /*
         * If we are using egde IRQs, new samples arrived while processing
         * the IRQ and those may be missed unless we pick them here, so poll
         * again. If the sensor delivery frequency is very high, this thread
         * turns into a polled loop handler.
         */
        while (sdata->hw_irq_trigger &&
               st_sensors_new_samples_available(indio_dev, sdata)) {
                dev_dbg(sdata->dev, "more samples came in during polling\n");
                sdata->hw_timestamp = iio_get_time_ns(indio_dev);
                iio_trigger_poll_chained(p);
        }

        return IRQ_HANDLED;
}

int st_sensors_allocate_trigger(struct iio_dev *indio_dev,
                                const struct iio_trigger_ops *trigger_ops)
{
        int err, irq;
        struct st_sensor_data *sdata = iio_priv(indio_dev);
        unsigned long irq_trig;

        sdata->trig = iio_trigger_alloc("%s-trigger", indio_dev->name);
        if (sdata->trig == NULL) {
                dev_err(&indio_dev->dev, "failed to allocate iio trigger.\n");
                return -ENOMEM;
        }

        iio_trigger_set_drvdata(sdata->trig, indio_dev);
        sdata->trig->ops = trigger_ops;
        sdata->trig->dev.parent = sdata->dev;

        irq = sdata->get_irq_data_ready(indio_dev);
        irq_trig = irqd_get_trigger_type(irq_get_irq_data(irq));
        /*
         * If the IRQ is triggered on falling edge, we need to mark the
         * interrupt as active low, if the hardware supports this.
         */
        switch(irq_trig) {
        case IRQF_TRIGGER_FALLING:
        case IRQF_TRIGGER_LOW:
                if (!sdata->sensor_settings->drdy_irq.addr_ihl) {
                        dev_err(&indio_dev->dev,
                                "falling/low specified for IRQ "
                                "but hardware only support rising/high: "
                                "will request rising/high\n");
                        if (irq_trig == IRQF_TRIGGER_FALLING)
                                irq_trig = IRQF_TRIGGER_RISING;
                        if (irq_trig == IRQF_TRIGGER_LOW)
                                irq_trig = IRQF_TRIGGER_HIGH;
                } else {
                        /* Set up INT active low i.e. falling edge */
                        err = st_sensors_write_data_with_mask(indio_dev,
                                sdata->sensor_settings->drdy_irq.addr_ihl,
                                sdata->sensor_settings->drdy_irq.mask_ihl, 1);
                        if (err < 0)
                                goto iio_trigger_free;
                        dev_info(&indio_dev->dev,
                                 "interrupts on the falling edge or "
                                 "active low level\n");
                }
                break;
        case IRQF_TRIGGER_RISING:
                dev_info(&indio_dev->dev,
                         "interrupts on the rising edge\n");
                break;
        case IRQF_TRIGGER_HIGH:
                dev_info(&indio_dev->dev,
                         "interrupts active high level\n");
                break;
        default:
                /* This is the most preferred mode, if possible */
                dev_err(&indio_dev->dev,
                        "unsupported IRQ trigger specified (%lx), enforce "
                        "rising edge\n", irq_trig);
                irq_trig = IRQF_TRIGGER_RISING;
        }

        /* Tell the interrupt handler that we're dealing with edges */
        if (irq_trig == IRQF_TRIGGER_FALLING ||
            irq_trig == IRQF_TRIGGER_RISING)
                sdata->edge_irq = true;
        else
                /*
                 * If we're not using edges (i.e. level interrupts) we
                 * just mask off the IRQ, handle one interrupt, then
                 * if the line is still low, we return to the
                 * interrupt handler top half again and start over.
                 */
                irq_trig |= IRQF_ONESHOT;

        /*
         * If the interrupt pin is Open Drain, by definition this
         * means that the interrupt line may be shared with other
         * peripherals. But to do this we also need to have a status
         * register and mask to figure out if this sensor was firing
         * the IRQ or not, so we can tell the interrupt handle that
         * it was "our" interrupt.
         */
        if (sdata->int_pin_open_drain &&
            sdata->sensor_settings->drdy_irq.stat_drdy.addr)
                irq_trig |= IRQF_SHARED;

        err = request_threaded_irq(sdata->get_irq_data_ready(indio_dev),
                        st_sensors_irq_handler,
                        st_sensors_irq_thread,
                        irq_trig,
                        sdata->trig->name,
                        sdata->trig);
        if (err) {
                dev_err(&indio_dev->dev, "failed to request trigger IRQ.\n");
                goto iio_trigger_free;
        }

        err = iio_trigger_register(sdata->trig);
        if (err < 0) {
                dev_err(&indio_dev->dev, "failed to register iio trigger.\n");
                goto iio_trigger_register_error;
        }
        indio_dev->trig = iio_trigger_get(sdata->trig);

        return 0;

iio_trigger_register_error:
        free_irq(sdata->get_irq_data_ready(indio_dev), sdata->trig);
iio_trigger_free:
        iio_trigger_free(sdata->trig);
        return err;
}
EXPORT_SYMBOL(st_sensors_allocate_trigger);

void st_sensors_deallocate_trigger(struct iio_dev *indio_dev)
{
        struct st_sensor_data *sdata = iio_priv(indio_dev);

        iio_trigger_unregister(sdata->trig);
        free_irq(sdata->get_irq_data_ready(indio_dev), sdata->trig);
        iio_trigger_free(sdata->trig);
}
EXPORT_SYMBOL(st_sensors_deallocate_trigger);

int st_sensors_validate_device(struct iio_trigger *trig,
                               struct iio_dev *indio_dev)
{
        struct iio_dev *indio = iio_trigger_get_drvdata(trig);

        if (indio != indio_dev)
                return -EINVAL;

        return 0;
}
EXPORT_SYMBOL(st_sensors_validate_device);

MODULE_AUTHOR("Denis Ciocca <denis.ciocca@st.com>");
MODULE_DESCRIPTION("STMicroelectronics ST-sensors trigger");
MODULE_LICENSE("GPL v2");