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larsclausen
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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 <[email protected]> Signed-off-by: Jonathan Cameron <[email protected]>
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‎drivers/iio/buffer/Kconfig‎

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@@ -18,6 +18,17 @@ config IIO_BUFFER_DMA
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Should be selected by drivers that want to use the generic DMA buffer
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infrastructure.
2020

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config IIO_BUFFER_DMAENGINE
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tristate
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select IIO_BUFFER_DMA
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help
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Provides a bonding of the generic IIO DMA buffer infrastructure with the
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DMAengine framework. This can be used by converter drivers with a DMA port
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connected to an external DMA controller which is supported by the
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DMAengine framework.
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Should be selected by drivers that want to use this functionality.
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config IIO_KFIFO_BUF
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tristate "Industrial I/O buffering based on kfifo"
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help

‎drivers/iio/buffer/Makefile‎

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@@ -5,5 +5,6 @@
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# When adding new entries keep the list in alphabetical order
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obj-$(CONFIG_IIO_BUFFER_CB) += industrialio-buffer-cb.o
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obj-$(CONFIG_IIO_BUFFER_DMA) += industrialio-buffer-dma.o
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obj-$(CONFIG_IIO_BUFFER_DMAENGINE) += industrialio-buffer-dmaengine.o
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obj-$(CONFIG_IIO_TRIGGERED_BUFFER) += industrialio-triggered-buffer.o
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obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o

‎drivers/iio/buffer/industrialio-buffer-dmaengine.c‎

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/*
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* Copyright 2014-2015 Analog Devices Inc.
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* Author: Lars-Peter Clausen <[email protected]>
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*
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* Licensed under the GPL-2 or later.
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*/
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#include <linux/slab.h>
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#include <linux/kernel.h>
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#include <linux/dmaengine.h>
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#include <linux/dma-mapping.h>
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#include <linux/spinlock.h>
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#include <linux/err.h>
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#include <linux/iio/iio.h>
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#include <linux/iio/buffer.h>
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#include <linux/iio/buffer-dma.h>
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#include <linux/iio/buffer-dmaengine.h>
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/*
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* The IIO DMAengine buffer combines the generic IIO DMA buffer infrastructure
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* with the DMAengine framework. The generic IIO DMA buffer infrastructure is
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* used to manage the buffer memory and implement the IIO buffer operations
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* while the DMAengine framework is used to perform the DMA transfers. Combined
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* this results in a device independent fully functional DMA buffer
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* implementation that can be used by device drivers for peripherals which are
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* connected to a DMA controller which has a DMAengine driver implementation.
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*/
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struct dmaengine_buffer {
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struct iio_dma_buffer_queue queue;
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struct dma_chan *chan;
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struct list_head active;
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size_t align;
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size_t max_size;
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};
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static struct dmaengine_buffer *iio_buffer_to_dmaengine_buffer(
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struct iio_buffer *buffer)
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{
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return container_of(buffer, struct dmaengine_buffer, queue.buffer);
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}
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static void iio_dmaengine_buffer_block_done(void *data)
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{
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struct iio_dma_buffer_block *block = data;
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unsigned long flags;
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spin_lock_irqsave(&block->queue->list_lock, flags);
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list_del(&block->head);
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spin_unlock_irqrestore(&block->queue->list_lock, flags);
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iio_dma_buffer_block_done(block);
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}
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static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
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struct iio_dma_buffer_block *block)
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{
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struct dmaengine_buffer *dmaengine_buffer =
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iio_buffer_to_dmaengine_buffer(&queue->buffer);
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struct dma_async_tx_descriptor *desc;
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dma_cookie_t cookie;
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block->bytes_used = min(block->size, dmaengine_buffer->max_size);
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block->bytes_used = rounddown(block->bytes_used,
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dmaengine_buffer->align);
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desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
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block->phys_addr, block->bytes_used, DMA_DEV_TO_MEM,
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DMA_PREP_INTERRUPT);
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if (!desc)
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return -ENOMEM;
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desc->callback = iio_dmaengine_buffer_block_done;
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desc->callback_param = block;
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cookie = dmaengine_submit(desc);
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if (dma_submit_error(cookie))
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return dma_submit_error(cookie);
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spin_lock_irq(&dmaengine_buffer->queue.list_lock);
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list_add_tail(&block->head, &dmaengine_buffer->active);
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spin_unlock_irq(&dmaengine_buffer->queue.list_lock);
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dma_async_issue_pending(dmaengine_buffer->chan);
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return 0;
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}
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static void iio_dmaengine_buffer_abort(struct iio_dma_buffer_queue *queue)
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{
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struct dmaengine_buffer *dmaengine_buffer =
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iio_buffer_to_dmaengine_buffer(&queue->buffer);
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dmaengine_terminate_all(dmaengine_buffer->chan);
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/* FIXME: There is a slight chance of a race condition here.
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* dmaengine_terminate_all() does not guarantee that all transfer
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* callbacks have finished running. Need to introduce a
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* dmaengine_terminate_all_sync().
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*/
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iio_dma_buffer_block_list_abort(queue, &dmaengine_buffer->active);
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}
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static void iio_dmaengine_buffer_release(struct iio_buffer *buf)
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{
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struct dmaengine_buffer *dmaengine_buffer =
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iio_buffer_to_dmaengine_buffer(buf);
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iio_dma_buffer_release(&dmaengine_buffer->queue);
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kfree(dmaengine_buffer);
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}
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static const struct iio_buffer_access_funcs iio_dmaengine_buffer_ops = {
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.read_first_n = iio_dma_buffer_read,
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.set_bytes_per_datum = iio_dma_buffer_set_bytes_per_datum,
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.set_length = iio_dma_buffer_set_length,
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.request_update = iio_dma_buffer_request_update,
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.enable = iio_dma_buffer_enable,
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.disable = iio_dma_buffer_disable,
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.data_available = iio_dma_buffer_data_available,
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.release = iio_dmaengine_buffer_release,
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.modes = INDIO_BUFFER_HARDWARE,
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.flags = INDIO_BUFFER_FLAG_FIXED_WATERMARK,
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};
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static const struct iio_dma_buffer_ops iio_dmaengine_default_ops = {
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.submit = iio_dmaengine_buffer_submit_block,
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.abort = iio_dmaengine_buffer_abort,
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};
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/**
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* iio_dmaengine_buffer_alloc() - Allocate new buffer which uses DMAengine
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* @dev: Parent device for the buffer
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* @channel: DMA channel name, typically "rx".
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*
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* This allocates a new IIO buffer which internally uses the DMAengine framework
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* to perform its transfers. The parent device will be used to request the DMA
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* channel.
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*
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* Once done using the buffer iio_dmaengine_buffer_free() should be used to
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* release it.
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*/
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struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
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const char *channel)
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{
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struct dmaengine_buffer *dmaengine_buffer;
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unsigned int width, src_width, dest_width;
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struct dma_slave_caps caps;
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struct dma_chan *chan;
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int ret;
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dmaengine_buffer = kzalloc(sizeof(*dmaengine_buffer), GFP_KERNEL);
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if (!dmaengine_buffer)
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return ERR_PTR(-ENOMEM);
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chan = dma_request_slave_channel_reason(dev, channel);
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if (IS_ERR(chan)) {
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ret = PTR_ERR(chan);
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goto err_free;
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}
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ret = dma_get_slave_caps(chan, &caps);
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if (ret < 0)
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goto err_free;
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/* Needs to be aligned to the maximum of the minimums */
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if (caps.src_addr_widths)
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src_width = __ffs(caps.src_addr_widths);
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else
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src_width = 1;
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if (caps.dst_addr_widths)
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dest_width = __ffs(caps.dst_addr_widths);
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else
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dest_width = 1;
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width = max(src_width, dest_width);
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INIT_LIST_HEAD(&dmaengine_buffer->active);
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dmaengine_buffer->chan = chan;
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dmaengine_buffer->align = width;
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dmaengine_buffer->max_size = dma_get_max_seg_size(chan->device->dev);
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iio_dma_buffer_init(&dmaengine_buffer->queue, chan->device->dev,
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&iio_dmaengine_default_ops);
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dmaengine_buffer->queue.buffer.access = &iio_dmaengine_buffer_ops;
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return &dmaengine_buffer->queue.buffer;
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err_free:
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kfree(dmaengine_buffer);
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return ERR_PTR(ret);
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}
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EXPORT_SYMBOL(iio_dmaengine_buffer_alloc);
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/**
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* iio_dmaengine_buffer_free() - Free dmaengine buffer
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* @buffer: Buffer to free
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*
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* Frees a buffer previously allocated with iio_dmaengine_buffer_alloc().
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*/
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void iio_dmaengine_buffer_free(struct iio_buffer *buffer)
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{
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struct dmaengine_buffer *dmaengine_buffer =
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iio_buffer_to_dmaengine_buffer(buffer);
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iio_dma_buffer_exit(&dmaengine_buffer->queue);
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dma_release_channel(dmaengine_buffer->chan);
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iio_buffer_put(buffer);
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}
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EXPORT_SYMBOL_GPL(iio_dmaengine_buffer_free);

‎include/linux/iio/buffer-dmaengine.h‎

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/*
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* Copyright 2014-2015 Analog Devices Inc.
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* Author: Lars-Peter Clausen <[email protected]>
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*
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* Licensed under the GPL-2 or later.
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*/
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#ifndef __IIO_DMAENGINE_H__
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#define __IIO_DMAENGINE_H__
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struct iio_buffer;
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struct device;
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struct iio_buffer *iio_dmaengine_buffer_alloc(struct device *dev,
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const char *channel);
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void iio_dmaengine_buffer_free(struct iio_buffer *buffer);
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#endif

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