iio: Add a DMAengine framework based buffer

Add a generic fully device independent DMA buffer implementation that uses
the DMAegnine framework to perform the DMA transfers. This can be used by
converter drivers that whish to provide a DMA buffer for converters that
are connected to a DMA core that implements the DMAengine API.

Apart from allocating the buffer using iio_dmaengine_buffer_alloc() and
freeing it using iio_dmaengine_buffer_free() no additional converter driver
specific code is required when using this DMA buffer implementation.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 213 insertions, 0 deletions

diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
new file mode 100644
index 000000000000..ebdb838d3a1c
--- /dev/null
+++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
@@ -0,0 +1,213 @@
+/*
+ * Copyright 2014-2015 Analog Devices Inc.
+ *  Author: Lars-Peter Clausen <lars@metafoo.de>
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-mapping.h>
+#include <linux/spinlock.h>
+#include <linux/err.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/buffer.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)
+{
+        struct iio_dma_buffer_block *block = data;
+        unsigned long flags;
+
+        spin_lock_irqsave(&block->queue->list_lock, flags);
+        list_del(&block->head);
+        spin_unlock_irqrestore(&block->queue->list_lock, flags);
+        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;
+        dma_cookie_t cookie;
+
+        block->bytes_used = min(block->size, dmaengine_buffer->max_size);
+        block->bytes_used = rounddown(block->bytes_used,
+                        dmaengine_buffer->align);
+
+        desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
+                block->phys_addr, block->bytes_used, DMA_DEV_TO_MEM,
+                DMA_PREP_INTERRUPT);
+        if (!desc)
+                return -ENOMEM;
+
+        desc->callback = iio_dmaengine_buffer_block_done;
+        desc->callback_param = block;
+
+        cookie = dmaengine_submit(desc);
+        if (dma_submit_error(cookie))
+                return dma_submit_error(cookie);
+
+        spin_lock_irq(&dmaengine_buffer->queue.list_lock);
+        list_add_tail(&block->head, &dmaengine_buffer->active);
+        spin_unlock_irq(&dmaengine_buffer->queue.list_lock);
+
+        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_all(dmaengine_buffer->chan);
+        /* FIXME: There is a slight chance of a race condition here.
+         * dmaengine_terminate_all() does not guarantee that all transfer
+         * callbacks have finished running. Need to introduce a
+         * dmaengine_terminate_all_sync().
+         */
+        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_first_n = iio_dma_buffer_read,
+        .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_data_available,
+        .release = iio_dmaengine_buffer_release,
+
+        .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,
+};
+
+/**
+ * iio_dmaengine_buffer_alloc() - Allocate new buffer which uses DMAengine
+ * @dev: Parent device for the buffer
+ * @channel: DMA channel name, typically "rx".
+ *
+ * This allocates a new IIO buffer which internally uses the DMAengine framework
+ * to perform its transfers. The parent device will be used to request the DMA
+ * channel.
+ *
+ * Once done using the buffer iio_dmaengine_buffer_free() should be used to
+ * release it.
+ */
+struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
+        const char *channel)
+{
+        struct dmaengine_buffer *dmaengine_buffer;
+        unsigned int width, src_width, dest_width;
+        struct dma_slave_caps caps;
+        struct dma_chan *chan;
+        int ret;
+
+        dmaengine_buffer = kzalloc(sizeof(*dmaengine_buffer), GFP_KERNEL);
+        if (!dmaengine_buffer)
+                return ERR_PTR(-ENOMEM);
+
+        chan = dma_request_slave_channel_reason(dev, channel);
+        if (IS_ERR(chan)) {
+                ret = PTR_ERR(chan);
+                goto err_free;
+        }
+
+        ret = dma_get_slave_caps(chan, &caps);
+        if (ret < 0)
+                goto err_free;
+
+        /* 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.access = &iio_dmaengine_buffer_ops;
+
+        return &dmaengine_buffer->queue.buffer;
+
+err_free:
+        kfree(dmaengine_buffer);
+        return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(iio_dmaengine_buffer_alloc);
+
+/**
+ * iio_dmaengine_buffer_free() - Free dmaengine buffer
+ * @buffer: Buffer to free
+ *
+ * Frees a buffer previously allocated with iio_dmaengine_buffer_alloc().
+ */
+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);
+        dma_release_channel(dmaengine_buffer->chan);
+
+        iio_buffer_put(buffer);
+}
+EXPORT_SYMBOL_GPL(iio_dmaengine_buffer_free);