// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2014-2015 Analog Devices Inc.
 *  Author: Lars-Peter Clausen <lars@metafoo.de>
 */

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/cleanup.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/spinlock.h>
#include <linux/err.h>
#include <linux/module.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/buffer_impl.h>
#include <linux/iio/buffer-dma.h>
#include <linux/iio/buffer-dmaengine.h>

/*
 * The IIO DMAengine buffer combines the generic IIO DMA buffer infrastructure
 * with the DMAengine framework. The generic IIO DMA buffer infrastructure is
 * used to manage the buffer memory and implement the IIO buffer operations
 * while the DMAengine framework is used to perform the DMA transfers. Combined
 * this results in a device independent fully functional DMA buffer
 * implementation that can be used by device drivers for peripherals which are
 * connected to a DMA controller which has a DMAengine driver implementation.
 */

struct dmaengine_buffer {
        struct iio_dma_buffer_queue queue;

        struct dma_chan *chan;
        struct list_head active;

        size_t align;
        size_t max_size;
};

static struct dmaengine_buffer *iio_buffer_to_dmaengine_buffer(struct iio_buffer *buffer)
{
        return container_of(buffer, struct dmaengine_buffer, queue.buffer);
}

static void iio_dmaengine_buffer_block_done(void *data,
                                            const struct dmaengine_result *result)
{
        struct iio_dma_buffer_block *block = data;

        scoped_guard(spinlock_irqsave, &block->queue->list_lock)
                list_del(&block->head);
        block->bytes_used -= result->residue;
        iio_dma_buffer_block_done(block);
}

static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
                                             struct iio_dma_buffer_block *block)
{
        struct dmaengine_buffer *dmaengine_buffer =
                iio_buffer_to_dmaengine_buffer(&queue->buffer);
        struct dma_async_tx_descriptor *desc;
        enum dma_transfer_direction dma_dir;
        struct scatterlist *sgl;
        struct dma_vec *vecs;
        size_t max_size;
        dma_cookie_t cookie;
        size_t len_total;
        unsigned int i;
        int nents;

        max_size = min(block->size, dmaengine_buffer->max_size);
        max_size = round_down(max_size, dmaengine_buffer->align);

        if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN)
                dma_dir = DMA_DEV_TO_MEM;
        else
                dma_dir = DMA_MEM_TO_DEV;

        if (block->sg_table) {
                sgl = block->sg_table->sgl;
                nents = sg_nents_for_len(sgl, block->bytes_used);
                if (nents < 0)
                        return nents;

                vecs = kmalloc_array(nents, sizeof(*vecs), GFP_ATOMIC);
                if (!vecs)
                        return -ENOMEM;

                len_total = block->bytes_used;

                for (i = 0; i < nents; i++) {
                        vecs[i].addr = sg_dma_address(sgl);
                        vecs[i].len = min(sg_dma_len(sgl), len_total);
                        len_total -= vecs[i].len;

                        sgl = sg_next(sgl);
                }

                desc = dmaengine_prep_peripheral_dma_vec(dmaengine_buffer->chan,
                                                         vecs, nents, dma_dir,
                                                         DMA_PREP_INTERRUPT);
                kfree(vecs);
        } else {
                max_size = min(block->size, dmaengine_buffer->max_size);
                max_size = round_down(max_size, dmaengine_buffer->align);

                if (queue->buffer.direction == IIO_BUFFER_DIRECTION_IN)
                        block->bytes_used = max_size;

                if (!block->bytes_used || block->bytes_used > max_size)
                        return -EINVAL;

                desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
                                                   block->phys_addr,
                                                   block->bytes_used,
                                                   dma_dir,
                                                   DMA_PREP_INTERRUPT);
        }
        if (!desc)
                return -ENOMEM;

        desc->callback_result = iio_dmaengine_buffer_block_done;
        desc->callback_param = block;

        cookie = dmaengine_submit(desc);
        if (dma_submit_error(cookie))
                return dma_submit_error(cookie);

        scoped_guard(spinlock_irq, &dmaengine_buffer->queue.list_lock)
                list_add_tail(&block->head, &dmaengine_buffer->active);

        dma_async_issue_pending(dmaengine_buffer->chan);

        return 0;
}

static void iio_dmaengine_buffer_abort(struct iio_dma_buffer_queue *queue)
{
        struct dmaengine_buffer *dmaengine_buffer =
                iio_buffer_to_dmaengine_buffer(&queue->buffer);

        dmaengine_terminate_sync(dmaengine_buffer->chan);
        iio_dma_buffer_block_list_abort(queue, &dmaengine_buffer->active);
}

static void iio_dmaengine_buffer_release(struct iio_buffer *buf)
{
        struct dmaengine_buffer *dmaengine_buffer =
                iio_buffer_to_dmaengine_buffer(buf);

        iio_dma_buffer_release(&dmaengine_buffer->queue);
        kfree(dmaengine_buffer);
}

static const struct iio_buffer_access_funcs iio_dmaengine_buffer_ops = {
        .read = iio_dma_buffer_read,
        .write = iio_dma_buffer_write,
        .set_bytes_per_datum = iio_dma_buffer_set_bytes_per_datum,
        .set_length = iio_dma_buffer_set_length,
        .request_update = iio_dma_buffer_request_update,
        .enable = iio_dma_buffer_enable,
        .disable = iio_dma_buffer_disable,
        .data_available = iio_dma_buffer_usage,
        .space_available = iio_dma_buffer_usage,
        .release = iio_dmaengine_buffer_release,

        .enqueue_dmabuf = iio_dma_buffer_enqueue_dmabuf,
        .attach_dmabuf = iio_dma_buffer_attach_dmabuf,
        .detach_dmabuf = iio_dma_buffer_detach_dmabuf,

        .lock_queue = iio_dma_buffer_lock_queue,
        .unlock_queue = iio_dma_buffer_unlock_queue,

        .get_dma_dev = iio_dma_buffer_get_dma_dev,

        .modes = INDIO_BUFFER_HARDWARE,
        .flags = INDIO_BUFFER_FLAG_FIXED_WATERMARK,
};

static const struct iio_dma_buffer_ops iio_dmaengine_default_ops = {
        .submit = iio_dmaengine_buffer_submit_block,
        .abort = iio_dmaengine_buffer_abort,
};

static ssize_t iio_dmaengine_buffer_get_length_align(struct device *dev,
                                                     struct device_attribute *attr, char *buf)
{
        struct iio_buffer *buffer = to_iio_dev_attr(attr)->buffer;
        struct dmaengine_buffer *dmaengine_buffer =
                iio_buffer_to_dmaengine_buffer(buffer);

        return sysfs_emit(buf, "%zu\n", dmaengine_buffer->align);
}

static IIO_DEVICE_ATTR(length_align_bytes, 0444,
                       iio_dmaengine_buffer_get_length_align, NULL, 0);

static const struct iio_dev_attr *iio_dmaengine_buffer_attrs[] = {
        &iio_dev_attr_length_align_bytes,
        NULL,
};

/**
 * iio_dmaengine_buffer_alloc() - Allocate new buffer which uses DMAengine
 * @chan: DMA channel.
 *
 * This allocates a new IIO buffer which internally uses the DMAengine framework
 * to perform its transfers.
 *
 * Once done using the buffer iio_dmaengine_buffer_free() should be used to
 * release it.
 */
static struct iio_buffer *iio_dmaengine_buffer_alloc(struct dma_chan *chan)
{
        struct dmaengine_buffer *dmaengine_buffer;
        unsigned int width, src_width, dest_width;
        struct dma_slave_caps caps;
        int ret;

        ret = dma_get_slave_caps(chan, &caps);
        if (ret < 0)
                return ERR_PTR(ret);

        dmaengine_buffer = kzalloc_obj(*dmaengine_buffer);
        if (!dmaengine_buffer)
                return ERR_PTR(-ENOMEM);

        /* Needs to be aligned to the maximum of the minimums */
        if (caps.src_addr_widths)
                src_width = __ffs(caps.src_addr_widths);
        else
                src_width = 1;
        if (caps.dst_addr_widths)
                dest_width = __ffs(caps.dst_addr_widths);
        else
                dest_width = 1;
        width = max(src_width, dest_width);

        INIT_LIST_HEAD(&dmaengine_buffer->active);
        dmaengine_buffer->chan = chan;
        dmaengine_buffer->align = width;
        dmaengine_buffer->max_size = dma_get_max_seg_size(chan->device->dev);

        iio_dma_buffer_init(&dmaengine_buffer->queue, chan->device->dev,
                            &iio_dmaengine_default_ops);

        dmaengine_buffer->queue.buffer.attrs = iio_dmaengine_buffer_attrs;
        dmaengine_buffer->queue.buffer.access = &iio_dmaengine_buffer_ops;

        return &dmaengine_buffer->queue.buffer;
}

/**
 * iio_dmaengine_buffer_free() - Free dmaengine buffer
 * @buffer: Buffer to free
 *
 * Frees a buffer previously allocated with iio_dmaengine_buffer_alloc().
 */
static void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
{
        struct dmaengine_buffer *dmaengine_buffer =
                iio_buffer_to_dmaengine_buffer(buffer);

        iio_dma_buffer_exit(&dmaengine_buffer->queue);
        iio_buffer_put(buffer);
}

/**
 * iio_dmaengine_buffer_teardown() - Releases DMA channel and frees buffer
 * @buffer: Buffer to free
 *
 * Releases the DMA channel and frees the buffer previously setup with
 * iio_dmaengine_buffer_setup_ext().
 */
void iio_dmaengine_buffer_teardown(struct iio_buffer *buffer)
{
        struct dmaengine_buffer *dmaengine_buffer =
                iio_buffer_to_dmaengine_buffer(buffer);
        struct dma_chan *chan = dmaengine_buffer->chan;

        iio_dmaengine_buffer_free(buffer);
        dma_release_channel(chan);
}
EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_teardown, "IIO_DMAENGINE_BUFFER");

static struct iio_buffer
*__iio_dmaengine_buffer_setup_ext(struct iio_dev *indio_dev,
                                  struct dma_chan *chan,
                                  enum iio_buffer_direction dir)
{
        struct iio_buffer *buffer;
        int ret;

        buffer = iio_dmaengine_buffer_alloc(chan);
        if (IS_ERR(buffer))
                return ERR_CAST(buffer);

        indio_dev->modes |= INDIO_BUFFER_HARDWARE;

        buffer->direction = dir;

        ret = iio_device_attach_buffer(indio_dev, buffer);
        if (ret) {
                iio_dmaengine_buffer_free(buffer);
                return ERR_PTR(ret);
        }

        return buffer;
}

/**
 * iio_dmaengine_buffer_setup_ext() - Setup a DMA buffer for an IIO device
 * @dev: DMA channel consumer device
 * @indio_dev: IIO device to which to attach this buffer.
 * @channel: DMA channel name, typically "rx".
 * @dir: Direction of buffer (in or out)
 *
 * This allocates a new IIO buffer with devm_iio_dmaengine_buffer_alloc()
 * and attaches it to an IIO device with iio_device_attach_buffer().
 * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of the
 * IIO device.
 *
 * Once done using the buffer iio_dmaengine_buffer_teardown() should be used to
 * release it.
 */
struct iio_buffer *iio_dmaengine_buffer_setup_ext(struct device *dev,
                                                  struct iio_dev *indio_dev,
                                                  const char *channel,
                                                  enum iio_buffer_direction dir)
{
        struct dma_chan *chan;
        struct iio_buffer *buffer;

        chan = dma_request_chan(dev, channel);
        if (IS_ERR(chan))
                return ERR_CAST(chan);

        buffer = __iio_dmaengine_buffer_setup_ext(indio_dev, chan, dir);
        if (IS_ERR(buffer))
                dma_release_channel(chan);

        return buffer;
}
EXPORT_SYMBOL_NS_GPL(iio_dmaengine_buffer_setup_ext, "IIO_DMAENGINE_BUFFER");

static void devm_iio_dmaengine_buffer_teardown(void *buffer)
{
        iio_dmaengine_buffer_teardown(buffer);
}

/**
 * devm_iio_dmaengine_buffer_setup_ext() - Setup a DMA buffer for an IIO device
 * @dev: Device for devm ownership and DMA channel consumer device
 * @indio_dev: IIO device to which to attach this buffer.
 * @channel: DMA channel name, typically "rx".
 * @dir: Direction of buffer (in or out)
 *
 * This allocates a new IIO buffer with devm_iio_dmaengine_buffer_alloc()
 * and attaches it to an IIO device with iio_device_attach_buffer().
 * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of the
 * IIO device.
 */
int devm_iio_dmaengine_buffer_setup_ext(struct device *dev,
                                        struct iio_dev *indio_dev,
                                        const char *channel,
                                        enum iio_buffer_direction dir)
{
        struct iio_buffer *buffer;

        buffer = iio_dmaengine_buffer_setup_ext(dev, indio_dev, channel, dir);
        if (IS_ERR(buffer))
                return PTR_ERR(buffer);

        return devm_add_action_or_reset(dev, devm_iio_dmaengine_buffer_teardown,
                                        buffer);
}
EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_ext, "IIO_DMAENGINE_BUFFER");

static void devm_iio_dmaengine_buffer_free(void *buffer)
{
        iio_dmaengine_buffer_free(buffer);
}

/**
 * devm_iio_dmaengine_buffer_setup_with_handle() - Setup a DMA buffer for an
 *                                                 IIO device
 * @dev: Device for devm ownership
 * @indio_dev: IIO device to which to attach this buffer.
 * @chan: DMA channel
 * @dir: Direction of buffer (in or out)
 *
 * This allocates a new IIO buffer with devm_iio_dmaengine_buffer_alloc()
 * and attaches it to an IIO device with iio_device_attach_buffer().
 * It also appends the INDIO_BUFFER_HARDWARE mode to the supported modes of the
 * IIO device.
 *
 * This is the same as devm_iio_dmaengine_buffer_setup_ext() except that the
 * caller manages requesting and releasing the DMA channel handle.
 */
int devm_iio_dmaengine_buffer_setup_with_handle(struct device *dev,
                                                struct iio_dev *indio_dev,
                                                struct dma_chan *chan,
                                                enum iio_buffer_direction dir)
{
        struct iio_buffer *buffer;

        buffer = __iio_dmaengine_buffer_setup_ext(indio_dev, chan, dir);
        if (IS_ERR(buffer))
                return PTR_ERR(buffer);

        return devm_add_action_or_reset(dev, devm_iio_dmaengine_buffer_free,
                                        buffer);
}
EXPORT_SYMBOL_NS_GPL(devm_iio_dmaengine_buffer_setup_with_handle,
                     "IIO_DMAENGINE_BUFFER");

MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
MODULE_DESCRIPTION("DMA buffer for the IIO framework");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS("IIO_DMA_BUFFER");