pcf50633-adc.c

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/* NXP PCF50633 ADC Driver
 *
 * (C) 2006-2008 by Openmoko, Inc.
 * Author: Balaji Rao <[email protected]>
 * 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/slab.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;
    void (*callback)(struct pcf50633 *, void *, int);
    void *callback_param;
};

struct pcf50633_adc_sync_request {
    int result;
    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_sync_request *req = param;

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

int pcf50633_adc_sync_read(struct pcf50633 *pcf, int mux, int avg)
{
    struct pcf50633_adc_sync_request req;
    int ret;

    init_completion(&req.completion);

    ret = pcf50633_adc_async_read(pcf, mux, avg,
        pcf50633_adc_sync_read_callback, &req);
    if (ret)
        return ret;

    wait_for_completion(&req.completion);

    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_adc *adc;

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

    adc->pcf = dev_to_pcf50633(pdev->dev.parent);
    platform_set_drvdata(pdev, adc);

    pcf50633_register_irq(adc->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),
};

module_platform_driver(pcf50633_adc_driver);

MODULE_AUTHOR("Balaji Rao <[email protected]>");
MODULE_DESCRIPTION("PCF50633 adc driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:pcf50633-adc");