/* NXP PCF50633 ADC Driver
 *
 * (C) 2006-2008 by Openmoko, Inc.
 * Author: Balaji Rao <balajirrao@openmoko.org>
 * All rights reserved.
 *
 * Broken down from monstrous PCF50633 driver mainly by
 * Harald Welte, Andy Green and Werner Almesberger
 *
 *  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.
 *
 *  NOTE: This driver does not yet support subtractive ADC mode, which means
 *  you can do only one measurement per read request.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/completion.h>

#include <linux/mfd/pcf50633/core.h>
#include <linux/mfd/pcf50633/adc.h>

struct pcf50633_adc_request {
        int mux;
        int avg;
        int result;
        void (*callback)(struct pcf50633 *, void *, int);
        void *callback_param;

        /* Used in case of sync requests */
        struct completion completion;

};

#define PCF50633_MAX_ADC_FIFO_DEPTH 8

struct pcf50633_adc {
        struct pcf50633 *pcf;

        /* Private stuff */
        struct pcf50633_adc_request *queue[PCF50633_MAX_ADC_FIFO_DEPTH];
        int queue_head;
        int queue_tail;
        struct mutex queue_mutex;
};

static inline struct pcf50633_adc *__to_adc(struct pcf50633 *pcf)
{
        return platform_get_drvdata(pcf->adc_pdev);
}

static void adc_setup(struct pcf50633 *pcf, int channel, int avg)
{
        channel &= PCF50633_ADCC1_ADCMUX_MASK;

        /* kill ratiometric, but enable ACCSW biasing */
        pcf50633_reg_write(pcf, PCF50633_REG_ADCC2, 0x00);
        pcf50633_reg_write(pcf, PCF50633_REG_ADCC3, 0x01);

        /* start ADC conversion on selected channel */
        pcf50633_reg_write(pcf, PCF50633_REG_ADCC1, channel | avg |
                    PCF50633_ADCC1_ADCSTART | PCF50633_ADCC1_RES_10BIT);
}

static void trigger_next_adc_job_if_any(struct pcf50633 *pcf)
{
        struct pcf50633_adc *adc = __to_adc(pcf);
        int head;

        head = adc->queue_head;

        if (!adc->queue[head])
                return;

        adc_setup(pcf, adc->queue[head]->mux, adc->queue[head]->avg);
}

static int
adc_enqueue_request(struct pcf50633 *pcf, struct pcf50633_adc_request *req)
{
        struct pcf50633_adc *adc = __to_adc(pcf);
        int head, tail;

        mutex_lock(&adc->queue_mutex);

        head = adc->queue_head;
        tail = adc->queue_tail;

        if (adc->queue[tail]) {
                mutex_unlock(&adc->queue_mutex);
                dev_err(pcf->dev, "ADC queue is full, dropping request\n");
                return -EBUSY;
        }

        adc->queue[tail] = req;
        if (head == tail)
                trigger_next_adc_job_if_any(pcf);
        adc->queue_tail = (tail + 1) & (PCF50633_MAX_ADC_FIFO_DEPTH - 1);

        mutex_unlock(&adc->queue_mutex);

        return 0;
}

static void
pcf50633_adc_sync_read_callback(struct pcf50633 *pcf, void *param, int result)
{
        struct pcf50633_adc_request *req = param;

        req->result = result;
        complete(&req->completion);
}

int pcf50633_adc_sync_read(struct pcf50633 *pcf, int mux, int avg)
{
        struct pcf50633_adc_request *req;
        int err;

        /* req is freed when the result is ready, in interrupt handler */
        req = kzalloc(sizeof(*req), GFP_KERNEL);
        if (!req)
                return -ENOMEM;

        req->mux = mux;
        req->avg = avg;
        req->callback =  pcf50633_adc_sync_read_callback;
        req->callback_param = req;

        init_completion(&req->completion);
        err = adc_enqueue_request(pcf, req);
        if (err)
                return err;

        wait_for_completion(&req->completion);

        /* FIXME by this time req might be already freed */
        return req->result;
}
EXPORT_SYMBOL_GPL(pcf50633_adc_sync_read);

int pcf50633_adc_async_read(struct pcf50633 *pcf, int mux, int avg,
                             void (*callback)(struct pcf50633 *, void *, int),
                             void *callback_param)
{
        struct pcf50633_adc_request *req;

        /* req is freed when the result is ready, in interrupt handler */
        req = kmalloc(sizeof(*req), GFP_KERNEL);
        if (!req)
                return -ENOMEM;

        req->mux = mux;
        req->avg = avg;
        req->callback = callback;
        req->callback_param = callback_param;

        return adc_enqueue_request(pcf, req);
}
EXPORT_SYMBOL_GPL(pcf50633_adc_async_read);

static int adc_result(struct pcf50633 *pcf)
{
        u8 adcs1, adcs3;
        u16 result;

        adcs1 = pcf50633_reg_read(pcf, PCF50633_REG_ADCS1);
        adcs3 = pcf50633_reg_read(pcf, PCF50633_REG_ADCS3);
        result = (adcs1 << 2) | (adcs3 & PCF50633_ADCS3_ADCDAT1L_MASK);

        dev_dbg(pcf->dev, "adc result = %d\n", result);

        return result;
}

static void pcf50633_adc_irq(int irq, void *data)
{
        struct pcf50633_adc *adc = data;
        struct pcf50633 *pcf = adc->pcf;
        struct pcf50633_adc_request *req;
        int head, res;

        mutex_lock(&adc->queue_mutex);
        head = adc->queue_head;

        req = adc->queue[head];
        if (WARN_ON(!req)) {
                dev_err(pcf->dev, "pcf50633-adc irq: ADC queue empty!\n");
                mutex_unlock(&adc->queue_mutex);
                return;
        }
        adc->queue[head] = NULL;
        adc->queue_head = (head + 1) &
                                      (PCF50633_MAX_ADC_FIFO_DEPTH - 1);

        res = adc_result(pcf);
        trigger_next_adc_job_if_any(pcf);

        mutex_unlock(&adc->queue_mutex);

        req->callback(pcf, req->callback_param, res);
        kfree(req);
}

static int __devinit pcf50633_adc_probe(struct platform_device *pdev)
{
        struct pcf50633_subdev_pdata *pdata = pdev->dev.platform_data;
        struct pcf50633_adc *adc;

        adc = kzalloc(sizeof(*adc), GFP_KERNEL);
        if (!adc)
                return -ENOMEM;

        adc->pcf = pdata->pcf;
        platform_set_drvdata(pdev, adc);

        pcf50633_register_irq(pdata->pcf, PCF50633_IRQ_ADCRDY,
                                        pcf50633_adc_irq, adc);

        mutex_init(&adc->queue_mutex);

        return 0;
}

static int __devexit pcf50633_adc_remove(struct platform_device *pdev)
{
        struct pcf50633_adc *adc = platform_get_drvdata(pdev);
        int i, head;

        pcf50633_free_irq(adc->pcf, PCF50633_IRQ_ADCRDY);

        mutex_lock(&adc->queue_mutex);
        head = adc->queue_head;

        if (WARN_ON(adc->queue[head]))
                dev_err(adc->pcf->dev,
                        "adc driver removed with request pending\n");

        for (i = 0; i < PCF50633_MAX_ADC_FIFO_DEPTH; i++)
                kfree(adc->queue[i]);

        mutex_unlock(&adc->queue_mutex);
        kfree(adc);

        return 0;
}

static struct platform_driver pcf50633_adc_driver = {
        .driver = {
                .name = "pcf50633-adc",
        },
        .probe = pcf50633_adc_probe,
        .remove = __devexit_p(pcf50633_adc_remove),
};

static int __init pcf50633_adc_init(void)
{
        return platform_driver_register(&pcf50633_adc_driver);
}
module_init(pcf50633_adc_init);

static void __exit pcf50633_adc_exit(void)
{
        platform_driver_unregister(&pcf50633_adc_driver);
}
module_exit(pcf50633_adc_exit);

MODULE_AUTHOR("Balaji Rao <balajirrao@openmoko.org>");
MODULE_DESCRIPTION("PCF50633 adc driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pcf50633-adc");