spear_adc.c

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/*
 * ST SPEAr ADC driver
 *
 * Copyright 2012 Stefan Roese <[email protected]>
 *
 * Licensed under the GPL-2.
 */

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/completion.h>
#include <linux/of.h>
#include <linux/of_address.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

/*
 * SPEAR registers definitions
 */

#define SCAN_RATE_LO(x)     ((x) & 0xFFFF)
#define SCAN_RATE_HI(x)     (((x) >> 0x10) & 0xFFFF)
#define CLK_LOW(x)      (((x) & 0xf) << 0)
#define CLK_HIGH(x)     (((x) & 0xf) << 4)

/* Bit definitions for SPEAR_ADC_STATUS */
#define START_CONVERSION    (1 << 0)
#define CHANNEL_NUM(x)      ((x) << 1)
#define ADC_ENABLE      (1 << 4)
#define AVG_SAMPLE(x)       ((x) << 5)
#define VREF_INTERNAL       (1 << 9)

#define DATA_MASK       0x03ff
#define DATA_BITS       10

#define MOD_NAME "spear-adc"

#define ADC_CHANNEL_NUM     8

#define CLK_MIN         2500000
#define CLK_MAX         20000000

struct adc_regs_spear3xx {
    u32 status;
    u32 average;
    u32 scan_rate;
    u32 clk;    /* Not avail for 1340 & 1310 */
    u32 ch_ctrl[ADC_CHANNEL_NUM];
    u32 ch_data[ADC_CHANNEL_NUM];
};

struct chan_data {
    u32 lsb;
    u32 msb;
};

struct adc_regs_spear6xx {
    u32 status;
    u32 pad[2];
    u32 clk;
    u32 ch_ctrl[ADC_CHANNEL_NUM];
    struct chan_data ch_data[ADC_CHANNEL_NUM];
    u32 scan_rate_lo;
    u32 scan_rate_hi;
    struct chan_data average;
};

struct spear_adc_info {
    struct device_node *np;
    struct adc_regs_spear3xx __iomem *adc_base_spear3xx;
    struct adc_regs_spear6xx __iomem *adc_base_spear6xx;
    struct clk *clk;
    struct completion completion;
    u32 current_clk;
    u32 sampling_freq;
    u32 avg_samples;
    u32 vref_external;
    u32 value;
};

/*
 * Functions to access some SPEAr ADC register. Abstracted into
 * static inline functions, because of different register offsets
 * on different SoC variants (SPEAr300 vs SPEAr600 etc).
 */
static void spear_adc_set_status(struct spear_adc_info *info, u32 val)
{
    __raw_writel(val, &info->adc_base_spear6xx->status);
}

static void spear_adc_set_clk(struct spear_adc_info *info, u32 val)
{
    u32 clk_high, clk_low, count;
    u32 apb_clk = clk_get_rate(info->clk);

    count = (apb_clk + val - 1) / val;
    clk_low = count / 2;
    clk_high = count - clk_low;
    info->current_clk = apb_clk / count;

    __raw_writel(CLK_LOW(clk_low) | CLK_HIGH(clk_high),
             &info->adc_base_spear6xx->clk);
}

static void spear_adc_set_ctrl(struct spear_adc_info *info, int n,
                   u32 val)
{
    __raw_writel(val, &info->adc_base_spear6xx->ch_ctrl[n]);
}

static u32 spear_adc_get_average(struct spear_adc_info *info)
{
    if (of_device_is_compatible(info->np, "st,spear600-adc")) {
        return __raw_readl(&info->adc_base_spear6xx->average.msb) &
            DATA_MASK;
    } else {
        return __raw_readl(&info->adc_base_spear3xx->average) &
            DATA_MASK;
    }
}

static void spear_adc_set_scanrate(struct spear_adc_info *info, u32 rate)
{
    if (of_device_is_compatible(info->np, "st,spear600-adc")) {
        __raw_writel(SCAN_RATE_LO(rate),
                 &info->adc_base_spear6xx->scan_rate_lo);
        __raw_writel(SCAN_RATE_HI(rate),
                 &info->adc_base_spear6xx->scan_rate_hi);
    } else {
        __raw_writel(rate, &info->adc_base_spear3xx->scan_rate);
    }
}

static int spear_read_raw(struct iio_dev *indio_dev,
              struct iio_chan_spec const *chan,
              int *val,
              int *val2,
              long mask)
{
    struct spear_adc_info *info = iio_priv(indio_dev);
    u32 scale_mv;
    u32 status;

    switch (mask) {
    case IIO_CHAN_INFO_RAW:
        mutex_lock(&indio_dev->mlock);

        status = CHANNEL_NUM(chan->channel) |
            AVG_SAMPLE(info->avg_samples) |
            START_CONVERSION | ADC_ENABLE;
        if (info->vref_external == 0)
            status |= VREF_INTERNAL;

        spear_adc_set_status(info, status);
        wait_for_completion(&info->completion); /* set by ISR */
        *val = info->value;

        mutex_unlock(&indio_dev->mlock);

        return IIO_VAL_INT;

    case IIO_CHAN_INFO_SCALE:
        scale_mv = (info->vref_external * 1000) >> DATA_BITS;
        *val =  scale_mv / 1000;
        *val2 = (scale_mv % 1000) * 1000;
        return IIO_VAL_INT_PLUS_MICRO;
    }

    return -EINVAL;
}

#define SPEAR_ADC_CHAN(idx) {               \
    .type = IIO_VOLTAGE,                \
    .indexed = 1,                   \
    .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT |   \
    IIO_CHAN_INFO_SCALE_SHARED_BIT,         \
    .channel = idx,                 \
    .scan_type = {                  \
        .sign = 'u',                \
        .storagebits = 16,          \
    },                      \
}

static const struct iio_chan_spec spear_adc_iio_channels[] = {
    SPEAR_ADC_CHAN(0),
    SPEAR_ADC_CHAN(1),
    SPEAR_ADC_CHAN(2),
    SPEAR_ADC_CHAN(3),
    SPEAR_ADC_CHAN(4),
    SPEAR_ADC_CHAN(5),
    SPEAR_ADC_CHAN(6),
    SPEAR_ADC_CHAN(7),
};

static irqreturn_t spear_adc_isr(int irq, void *dev_id)
{
    struct spear_adc_info *info = (struct spear_adc_info *)dev_id;

    /* Read value to clear IRQ */
    info->value = spear_adc_get_average(info);
    complete(&info->completion);

    return IRQ_HANDLED;
}

static int spear_adc_configure(struct spear_adc_info *info)
{
    int i;

    /* Reset ADC core */
    spear_adc_set_status(info, 0);
    __raw_writel(0, &info->adc_base_spear6xx->clk);
    for (i = 0; i < 8; i++)
        spear_adc_set_ctrl(info, i, 0);
    spear_adc_set_scanrate(info, 0);

    spear_adc_set_clk(info, info->sampling_freq);

    return 0;
}

static ssize_t spear_adc_read_frequency(struct device *dev,
                    struct device_attribute *attr,
                    char *buf)
{
    struct iio_dev *indio_dev = dev_to_iio_dev(dev);
    struct spear_adc_info *info = iio_priv(indio_dev);

    return sprintf(buf, "%d\n", info->current_clk);
}

static ssize_t spear_adc_write_frequency(struct device *dev,
                     struct device_attribute *attr,
                     const char *buf,
                     size_t len)
{
    struct iio_dev *indio_dev = dev_to_iio_dev(dev);
    struct spear_adc_info *info = iio_priv(indio_dev);
    u32 clk_high, clk_low, count;
    u32 apb_clk = clk_get_rate(info->clk);
    unsigned long lval;
    int ret;

    ret = kstrtoul(buf, 10, &lval);
    if (ret)
        return ret;

    mutex_lock(&indio_dev->mlock);

    if ((lval < CLK_MIN) || (lval > CLK_MAX)) {
        ret = -EINVAL;
        goto out;
    }

    count = (apb_clk + lval - 1) / lval;
    clk_low = count / 2;
    clk_high = count - clk_low;
    info->current_clk = apb_clk / count;
    spear_adc_set_clk(info, lval);

out:
    mutex_unlock(&indio_dev->mlock);

    return ret ? ret : len;
}

static IIO_DEV_ATTR_SAMP_FREQ(S_IWUSR | S_IRUGO,
                  spear_adc_read_frequency,
                  spear_adc_write_frequency);

static struct attribute *spear_attributes[] = {
    &iio_dev_attr_sampling_frequency.dev_attr.attr,
    NULL
};

static const struct attribute_group spear_attribute_group = {
    .attrs = spear_attributes,
};

static const struct iio_info spear_adc_iio_info = {
    .read_raw = &spear_read_raw,
    .attrs = &spear_attribute_group,
    .driver_module = THIS_MODULE,
};

static int __devinit spear_adc_probe(struct platform_device *pdev)
{
    struct device_node *np = pdev->dev.of_node;
    struct device *dev = &pdev->dev;
    struct spear_adc_info *info;
    struct iio_dev *iodev = NULL;
    int ret = -ENODEV;
    int irq;

    iodev = iio_device_alloc(sizeof(struct spear_adc_info));
    if (!iodev) {
        dev_err(dev, "failed allocating iio device\n");
        ret = -ENOMEM;
        goto errout1;
    }

    info = iio_priv(iodev);
    info->np = np;

    /*
     * SPEAr600 has a different register layout than other SPEAr SoC's
     * (e.g. SPEAr3xx). Let's provide two register base addresses
     * to support multi-arch kernels.
     */
    info->adc_base_spear6xx = of_iomap(np, 0);
    if (!info->adc_base_spear6xx) {
        dev_err(dev, "failed mapping memory\n");
        ret = -ENOMEM;
        goto errout2;
    }
    info->adc_base_spear3xx =
        (struct adc_regs_spear3xx *)info->adc_base_spear6xx;

    info->clk = clk_get(dev, NULL);
    if (IS_ERR(info->clk)) {
        dev_err(dev, "failed getting clock\n");
        goto errout3;
    }

    ret = clk_prepare_enable(info->clk);
    if (ret) {
        dev_err(dev, "failed enabling clock\n");
        goto errout4;
    }

    irq = platform_get_irq(pdev, 0);
    if ((irq < 0) || (irq >= NR_IRQS)) {
        dev_err(dev, "failed getting interrupt resource\n");
        ret = -EINVAL;
        goto errout5;
    }

    ret = devm_request_irq(dev, irq, spear_adc_isr, 0, MOD_NAME, info);
    if (ret < 0) {
        dev_err(dev, "failed requesting interrupt\n");
        goto errout5;
    }

    if (of_property_read_u32(np, "sampling-frequency",
                 &info->sampling_freq)) {
        dev_err(dev, "sampling-frequency missing in DT\n");
        ret = -EINVAL;
        goto errout5;
    }

    /*
     * Optional avg_samples defaults to 0, resulting in single data
     * conversion
     */
    of_property_read_u32(np, "average-samples", &info->avg_samples);

    /*
     * Optional vref_external defaults to 0, resulting in internal vref
     * selection
     */
    of_property_read_u32(np, "vref-external", &info->vref_external);

    spear_adc_configure(info);

    platform_set_drvdata(pdev, iodev);

    init_completion(&info->completion);

    iodev->name = MOD_NAME;
    iodev->dev.parent = dev;
    iodev->info = &spear_adc_iio_info;
    iodev->modes = INDIO_DIRECT_MODE;
    iodev->channels = spear_adc_iio_channels;
    iodev->num_channels = ARRAY_SIZE(spear_adc_iio_channels);

    ret = iio_device_register(iodev);
    if (ret)
        goto errout5;

    dev_info(dev, "SPEAR ADC driver loaded, IRQ %d\n", irq);

    return 0;

errout5:
    clk_disable_unprepare(info->clk);
errout4:
    clk_put(info->clk);
errout3:
    iounmap(info->adc_base_spear6xx);
errout2:
    iio_device_free(iodev);
errout1:
    return ret;
}

static int __devexit spear_adc_remove(struct platform_device *pdev)
{
    struct iio_dev *iodev = platform_get_drvdata(pdev);
    struct spear_adc_info *info = iio_priv(iodev);

    iio_device_unregister(iodev);
    platform_set_drvdata(pdev, NULL);
    clk_disable_unprepare(info->clk);
    clk_put(info->clk);
    iounmap(info->adc_base_spear6xx);
    iio_device_free(iodev);

    return 0;
}

static const struct of_device_id spear_adc_dt_ids[] = {
    { .compatible = "st,spear600-adc", },
    { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, spear_adc_dt_ids);

static struct platform_driver spear_adc_driver = {
    .probe      = spear_adc_probe,
    .remove     = __devexit_p(spear_adc_remove),
    .driver     = {
        .name   = MOD_NAME,
        .owner  = THIS_MODULE,
        .of_match_table = of_match_ptr(spear_adc_dt_ids),
    },
};

module_platform_driver(spear_adc_driver);

MODULE_AUTHOR("Stefan Roese <[email protected]>");
MODULE_DESCRIPTION("SPEAr ADC driver");
MODULE_LICENSE("GPL");