/*
 * sca3000_ring.c -- support VTI sca3000 series accelerometers via SPI
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * Copyright (c) 2009 Jonathan Cameron <jic23@kernel.org>
 *
 */

#include <linux/interrupt.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/spi/spi.h>
#include <linux/sysfs.h>
#include <linux/sched.h>
#include <linux/poll.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include "../ring_hw.h"
#include "sca3000.h"

/* RFC / future work
 *
 * The internal ring buffer doesn't actually change what it holds depending
 * on which signals are enabled etc, merely whether you can read them.
 * As such the scan mode selection is somewhat different than for a software
 * ring buffer and changing it actually covers any data already in the buffer.
 * Currently scan elements aren't configured so it doesn't matter.
 */

static int sca3000_read_data(struct sca3000_state *st,
                            uint8_t reg_address_high,
                            u8 **rx_p,
                            int len)
{
        int ret;
        struct spi_transfer xfer[2] = {
                {
                        .len = 1,
                        .tx_buf = st->tx,
                }, {
                        .len = len,
                }
        };
        *rx_p = kmalloc(len, GFP_KERNEL);
        if (*rx_p == NULL) {
                ret = -ENOMEM;
                goto error_ret;
        }
        xfer[1].rx_buf = *rx_p;
        st->tx[0] = SCA3000_READ_REG(reg_address_high);
        ret = spi_sync_transfer(st->us, xfer, ARRAY_SIZE(xfer));
        if (ret) {
                dev_err(get_device(&st->us->dev), "problem reading register");
                goto error_free_rx;
        }

        return 0;
error_free_rx:
        kfree(*rx_p);
error_ret:
        return ret;
}

/**
 * sca3000_read_first_n_hw_rb() - main ring access, pulls data from ring
 * @r:                  the ring
 * @count:              number of samples to try and pull
 * @data:               output the actual samples pulled from the hw ring
 *
 * Currently does not provide timestamps.  As the hardware doesn't add them they
 * can only be inferred approximately from ring buffer events such as 50% full
 * and knowledge of when buffer was last emptied.  This is left to userspace.
 **/
static int sca3000_read_first_n_hw_rb(struct iio_buffer *r,
                                      size_t count, char __user *buf)
{
        struct iio_hw_buffer *hw_ring = iio_to_hw_buf(r);
        struct iio_dev *indio_dev = hw_ring->private;
        struct sca3000_state *st = iio_priv(indio_dev);
        u8 *rx;
        int ret, i, num_available, num_read = 0;
        int bytes_per_sample = 1;

        if (st->bpse == 11)
                bytes_per_sample = 2;

        mutex_lock(&st->lock);
        if (count % bytes_per_sample) {
                ret = -EINVAL;
                goto error_ret;
        }

        ret = sca3000_read_data_short(st, SCA3000_REG_ADDR_BUF_COUNT, 1);
        if (ret)
                goto error_ret;
        else
                num_available = st->rx[0];
        /*
         * num_available is the total number of samples available
         * i.e. number of time points * number of channels.
         */
        if (count > num_available * bytes_per_sample)
                num_read = num_available*bytes_per_sample;
        else
                num_read = count;

        ret = sca3000_read_data(st,
                                SCA3000_REG_ADDR_RING_OUT,
                                &rx, num_read);
        if (ret)
                goto error_ret;

        for (i = 0; i < num_read; i++)
                *(((u16 *)rx) + i) = be16_to_cpup((u16 *)rx + i);

        if (copy_to_user(buf, rx, num_read))
                ret = -EFAULT;
        kfree(rx);
        r->stufftoread = 0;
error_ret:
        mutex_unlock(&st->lock);

        return ret ? ret : num_read;
}

/* This is only valid with all 3 elements enabled */
static int sca3000_ring_get_length(struct iio_buffer *r)
{
        return 64;
}

/* only valid if resolution is kept at 11bits */
static int sca3000_ring_get_bytes_per_datum(struct iio_buffer *r)
{
        return 6;
}

static IIO_BUFFER_ENABLE_ATTR;
static IIO_BUFFER_LENGTH_ATTR;

/**
 * sca3000_query_ring_int() is the hardware ring status interrupt enabled
 **/
static ssize_t sca3000_query_ring_int(struct device *dev,
                                      struct device_attribute *attr,
                                      char *buf)
{
        struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
        int ret, val;
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct sca3000_state *st = iio_priv(indio_dev);

        mutex_lock(&st->lock);
        ret = sca3000_read_data_short(st, SCA3000_REG_ADDR_INT_MASK, 1);
        val = st->rx[0];
        mutex_unlock(&st->lock);
        if (ret)
                return ret;

        return sprintf(buf, "%d\n", !!(val & this_attr->address));
}

/**
 * sca3000_set_ring_int() set state of ring status interrupt
 **/
static ssize_t sca3000_set_ring_int(struct device *dev,
                                      struct device_attribute *attr,
                                      const char *buf,
                                      size_t len)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct sca3000_state *st = iio_priv(indio_dev);
        struct iio_dev_attr *this_attr = to_iio_dev_attr(attr);
        long val;
        int ret;

        mutex_lock(&st->lock);
        ret = strict_strtol(buf, 10, &val);
        if (ret)
                goto error_ret;
        ret = sca3000_read_data_short(st, SCA3000_REG_ADDR_INT_MASK, 1);
        if (ret)
                goto error_ret;
        if (val)
                ret = sca3000_write_reg(st,
                                        SCA3000_REG_ADDR_INT_MASK,
                                        st->rx[0] | this_attr->address);
        else
                ret = sca3000_write_reg(st,
                                        SCA3000_REG_ADDR_INT_MASK,
                                        st->rx[0] & ~this_attr->address);
error_ret:
        mutex_unlock(&st->lock);

        return ret ? ret : len;
}

static IIO_DEVICE_ATTR(50_percent, S_IRUGO | S_IWUSR,
                       sca3000_query_ring_int,
                       sca3000_set_ring_int,
                       SCA3000_INT_MASK_RING_HALF);

static IIO_DEVICE_ATTR(75_percent, S_IRUGO | S_IWUSR,
                       sca3000_query_ring_int,
                       sca3000_set_ring_int,
                       SCA3000_INT_MASK_RING_THREE_QUARTER);

static ssize_t sca3000_show_buffer_scale(struct device *dev,
                                         struct device_attribute *attr,
                                         char *buf)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct sca3000_state *st = iio_priv(indio_dev);

        return sprintf(buf, "0.%06d\n", 4*st->info->scale);
}

static IIO_DEVICE_ATTR(in_accel_scale,
                       S_IRUGO,
                       sca3000_show_buffer_scale,
                       NULL,
                       0);

/*
 * Ring buffer attributes
 * This device is a bit unusual in that the sampling frequency and bpse
 * only apply to the ring buffer.  At all times full rate and accuracy
 * is available via direct reading from registers.
 */
static struct attribute *sca3000_ring_attributes[] = {
        &dev_attr_length.attr,
        &dev_attr_enable.attr,
        &iio_dev_attr_50_percent.dev_attr.attr,
        &iio_dev_attr_75_percent.dev_attr.attr,
        &iio_dev_attr_in_accel_scale.dev_attr.attr,
        NULL,
};

static struct attribute_group sca3000_ring_attr = {
        .attrs = sca3000_ring_attributes,
        .name = "buffer",
};

static struct iio_buffer *sca3000_rb_allocate(struct iio_dev *indio_dev)
{
        struct iio_buffer *buf;
        struct iio_hw_buffer *ring;

        ring = kzalloc(sizeof *ring, GFP_KERNEL);
        if (!ring)
                return NULL;

        ring->private = indio_dev;
        buf = &ring->buf;
        buf->stufftoread = 0;
        buf->attrs = &sca3000_ring_attr;
        iio_buffer_init(buf);

        return buf;
}

static inline void sca3000_rb_free(struct iio_buffer *r)
{
        kfree(iio_to_hw_buf(r));
}

static const struct iio_buffer_access_funcs sca3000_ring_access_funcs = {
        .read_first_n = &sca3000_read_first_n_hw_rb,
        .get_length = &sca3000_ring_get_length,
        .get_bytes_per_datum = &sca3000_ring_get_bytes_per_datum,
};

int sca3000_configure_ring(struct iio_dev *indio_dev)
{
        indio_dev->buffer = sca3000_rb_allocate(indio_dev);
        if (indio_dev->buffer == NULL)
                return -ENOMEM;
        indio_dev->modes |= INDIO_BUFFER_HARDWARE;

        indio_dev->buffer->access = &sca3000_ring_access_funcs;

        return 0;
}

void sca3000_unconfigure_ring(struct iio_dev *indio_dev)
{
        sca3000_rb_free(indio_dev->buffer);
}

static inline
int __sca3000_hw_ring_state_set(struct iio_dev *indio_dev, bool state)
{
        struct sca3000_state *st = iio_priv(indio_dev);
        int ret;

        mutex_lock(&st->lock);
        ret = sca3000_read_data_short(st, SCA3000_REG_ADDR_MODE, 1);
        if (ret)
                goto error_ret;
        if (state) {
                printk(KERN_INFO "supposedly enabling ring buffer\n");
                ret = sca3000_write_reg(st,
                                        SCA3000_REG_ADDR_MODE,
                                        (st->rx[0] | SCA3000_RING_BUF_ENABLE));
        } else
                ret = sca3000_write_reg(st,
                                        SCA3000_REG_ADDR_MODE,
                                        (st->rx[0] & ~SCA3000_RING_BUF_ENABLE));
error_ret:
        mutex_unlock(&st->lock);

        return ret;
}
/**
 * sca3000_hw_ring_preenable() hw ring buffer preenable function
 *
 * Very simple enable function as the chip will allows normal reads
 * during ring buffer operation so as long as it is indeed running
 * before we notify the core, the precise ordering does not matter.
 **/
static int sca3000_hw_ring_preenable(struct iio_dev *indio_dev)
{
        return __sca3000_hw_ring_state_set(indio_dev, 1);
}

static int sca3000_hw_ring_postdisable(struct iio_dev *indio_dev)
{
        return __sca3000_hw_ring_state_set(indio_dev, 0);
}

static const struct iio_buffer_setup_ops sca3000_ring_setup_ops = {
        .preenable = &sca3000_hw_ring_preenable,
        .postdisable = &sca3000_hw_ring_postdisable,
};

void sca3000_register_ring_funcs(struct iio_dev *indio_dev)
{
        indio_dev->setup_ops = &sca3000_ring_setup_ops;
}

/**
 * sca3000_ring_int_process() ring specific interrupt handling.
 *
 * This is only split from the main interrupt handler so as to
 * reduce the amount of code if the ring buffer is not enabled.
 **/
void sca3000_ring_int_process(u8 val, struct iio_buffer *ring)
{
        if (val & (SCA3000_INT_STATUS_THREE_QUARTERS |
                   SCA3000_INT_STATUS_HALF)) {
                ring->stufftoread = true;
                wake_up_interruptible(&ring->pollq);
        }
}