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Diffstat (limited to '')
| -rw-r--r-- | drivers/iio/buffer/industrialio-buffer-dma.c | 684 |
1 files changed, 684 insertions, 0 deletions
diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c new file mode 100644 index 000000000..b32bf5791 --- /dev/null +++ b/drivers/iio/buffer/industrialio-buffer-dma.c @@ -0,0 +1,684 @@ +/* + * Copyright 2013-2015 Analog Devices Inc. + * Author: Lars-Peter Clausen <lars@metafoo.de> + * + * Licensed under the GPL-2. + */ + +#include <linux/slab.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/device.h> +#include <linux/workqueue.h> +#include <linux/mutex.h> +#include <linux/sched.h> +#include <linux/poll.h> +#include <linux/iio/buffer.h> +#include <linux/iio/buffer_impl.h> +#include <linux/iio/buffer-dma.h> +#include <linux/dma-mapping.h> +#include <linux/sizes.h> + +/* + * For DMA buffers the storage is sub-divided into so called blocks. Each block + * has its own memory buffer. The size of the block is the granularity at which + * memory is exchanged between the hardware and the application. Increasing the + * basic unit of data exchange from one sample to one block decreases the + * management overhead that is associated with each sample. E.g. if we say the + * management overhead for one exchange is x and the unit of exchange is one + * sample the overhead will be x for each sample. Whereas when using a block + * which contains n samples the overhead per sample is reduced to x/n. This + * allows to achieve much higher samplerates than what can be sustained with + * the one sample approach. + * + * Blocks are exchanged between the DMA controller and the application via the + * means of two queues. The incoming queue and the outgoing queue. Blocks on the + * incoming queue are waiting for the DMA controller to pick them up and fill + * them with data. Block on the outgoing queue have been filled with data and + * are waiting for the application to dequeue them and read the data. + * + * A block can be in one of the following states: + * * Owned by the application. In this state the application can read data from + * the block. + * * On the incoming list: Blocks on the incoming list are queued up to be + * processed by the DMA controller. + * * Owned by the DMA controller: The DMA controller is processing the block + * and filling it with data. + * * On the outgoing list: Blocks on the outgoing list have been successfully + * processed by the DMA controller and contain data. They can be dequeued by + * the application. + * * Dead: A block that is dead has been marked as to be freed. It might still + * be owned by either the application or the DMA controller at the moment. + * But once they are done processing it instead of going to either the + * incoming or outgoing queue the block will be freed. + * + * In addition to this blocks are reference counted and the memory associated + * with both the block structure as well as the storage memory for the block + * will be freed when the last reference to the block is dropped. This means a + * block must not be accessed without holding a reference. + * + * The iio_dma_buffer implementation provides a generic infrastructure for + * managing the blocks. + * + * A driver for a specific piece of hardware that has DMA capabilities need to + * implement the submit() callback from the iio_dma_buffer_ops structure. This + * callback is supposed to initiate the DMA transfer copying data from the + * converter to the memory region of the block. Once the DMA transfer has been + * completed the driver must call iio_dma_buffer_block_done() for the completed + * block. + * + * Prior to this it must set the bytes_used field of the block contains + * the actual number of bytes in the buffer. Typically this will be equal to the + * size of the block, but if the DMA hardware has certain alignment requirements + * for the transfer length it might choose to use less than the full size. In + * either case it is expected that bytes_used is a multiple of the bytes per + * datum, i.e. the block must not contain partial samples. + * + * The driver must call iio_dma_buffer_block_done() for each block it has + * received through its submit_block() callback, even if it does not actually + * perform a DMA transfer for the block, e.g. because the buffer was disabled + * before the block transfer was started. In this case it should set bytes_used + * to 0. + * + * In addition it is recommended that a driver implements the abort() callback. + * It will be called when the buffer is disabled and can be used to cancel + * pending and stop active transfers. + * + * The specific driver implementation should use the default callback + * implementations provided by this module for the iio_buffer_access_funcs + * struct. It may overload some callbacks with custom variants if the hardware + * has special requirements that are not handled by the generic functions. If a + * driver chooses to overload a callback it has to ensure that the generic + * callback is called from within the custom callback. + */ + +static void iio_buffer_block_release(struct kref *kref) +{ + struct iio_dma_buffer_block *block = container_of(kref, + struct iio_dma_buffer_block, kref); + + WARN_ON(block->state != IIO_BLOCK_STATE_DEAD); + + dma_free_coherent(block->queue->dev, PAGE_ALIGN(block->size), + block->vaddr, block->phys_addr); + + iio_buffer_put(&block->queue->buffer); + kfree(block); +} + +static void iio_buffer_block_get(struct iio_dma_buffer_block *block) +{ + kref_get(&block->kref); +} + +static void iio_buffer_block_put(struct iio_dma_buffer_block *block) +{ + kref_put(&block->kref, iio_buffer_block_release); +} + +/* + * dma_free_coherent can sleep, hence we need to take some special care to be + * able to drop a reference from an atomic context. + */ +static LIST_HEAD(iio_dma_buffer_dead_blocks); +static DEFINE_SPINLOCK(iio_dma_buffer_dead_blocks_lock); + +static void iio_dma_buffer_cleanup_worker(struct work_struct *work) +{ + struct iio_dma_buffer_block *block, *_block; + LIST_HEAD(block_list); + + spin_lock_irq(&iio_dma_buffer_dead_blocks_lock); + list_splice_tail_init(&iio_dma_buffer_dead_blocks, &block_list); + spin_unlock_irq(&iio_dma_buffer_dead_blocks_lock); + + list_for_each_entry_safe(block, _block, &block_list, head) + iio_buffer_block_release(&block->kref); +} +static DECLARE_WORK(iio_dma_buffer_cleanup_work, iio_dma_buffer_cleanup_worker); + +static void iio_buffer_block_release_atomic(struct kref *kref) +{ + struct iio_dma_buffer_block *block; + unsigned long flags; + + block = container_of(kref, struct iio_dma_buffer_block, kref); + + spin_lock_irqsave(&iio_dma_buffer_dead_blocks_lock, flags); + list_add_tail(&block->head, &iio_dma_buffer_dead_blocks); + spin_unlock_irqrestore(&iio_dma_buffer_dead_blocks_lock, flags); + + schedule_work(&iio_dma_buffer_cleanup_work); +} + +/* + * Version of iio_buffer_block_put() that can be called from atomic context + */ +static void iio_buffer_block_put_atomic(struct iio_dma_buffer_block *block) +{ + kref_put(&block->kref, iio_buffer_block_release_atomic); +} + +static struct iio_dma_buffer_queue *iio_buffer_to_queue(struct iio_buffer *buf) +{ + return container_of(buf, struct iio_dma_buffer_queue, buffer); +} + +static struct iio_dma_buffer_block *iio_dma_buffer_alloc_block( + struct iio_dma_buffer_queue *queue, size_t size) +{ + struct iio_dma_buffer_block *block; + + block = kzalloc(sizeof(*block), GFP_KERNEL); + if (!block) + return NULL; + + block->vaddr = dma_alloc_coherent(queue->dev, PAGE_ALIGN(size), + &block->phys_addr, GFP_KERNEL); + if (!block->vaddr) { + kfree(block); + return NULL; + } + + block->size = size; + block->state = IIO_BLOCK_STATE_DEQUEUED; + block->queue = queue; + INIT_LIST_HEAD(&block->head); + kref_init(&block->kref); + + iio_buffer_get(&queue->buffer); + + return block; +} + +static void _iio_dma_buffer_block_done(struct iio_dma_buffer_block *block) +{ + struct iio_dma_buffer_queue *queue = block->queue; + + /* + * The buffer has already been freed by the application, just drop the + * reference. + */ + if (block->state != IIO_BLOCK_STATE_DEAD) { + block->state = IIO_BLOCK_STATE_DONE; + list_add_tail(&block->head, &queue->outgoing); + } +} + +/** + * iio_dma_buffer_block_done() - Indicate that a block has been completed + * @block: The completed block + * + * Should be called when the DMA controller has finished handling the block to + * pass back ownership of the block to the queue. + */ +void iio_dma_buffer_block_done(struct iio_dma_buffer_block *block) +{ + struct iio_dma_buffer_queue *queue = block->queue; + unsigned long flags; + + spin_lock_irqsave(&queue->list_lock, flags); + _iio_dma_buffer_block_done(block); + spin_unlock_irqrestore(&queue->list_lock, flags); + + iio_buffer_block_put_atomic(block); + wake_up_interruptible_poll(&queue->buffer.pollq, EPOLLIN | EPOLLRDNORM); +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_block_done); + +/** + * iio_dma_buffer_block_list_abort() - Indicate that a list block has been + * aborted + * @queue: Queue for which to complete blocks. + * @list: List of aborted blocks. All blocks in this list must be from @queue. + * + * Typically called from the abort() callback after the DMA controller has been + * stopped. This will set bytes_used to 0 for each block in the list and then + * hand the blocks back to the queue. + */ +void iio_dma_buffer_block_list_abort(struct iio_dma_buffer_queue *queue, + struct list_head *list) +{ + struct iio_dma_buffer_block *block, *_block; + unsigned long flags; + + spin_lock_irqsave(&queue->list_lock, flags); + list_for_each_entry_safe(block, _block, list, head) { + list_del(&block->head); + block->bytes_used = 0; + _iio_dma_buffer_block_done(block); + iio_buffer_block_put_atomic(block); + } + spin_unlock_irqrestore(&queue->list_lock, flags); + + wake_up_interruptible_poll(&queue->buffer.pollq, EPOLLIN | EPOLLRDNORM); +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_block_list_abort); + +static bool iio_dma_block_reusable(struct iio_dma_buffer_block *block) +{ + /* + * If the core owns the block it can be re-used. This should be the + * default case when enabling the buffer, unless the DMA controller does + * not support abort and has not given back the block yet. + */ + switch (block->state) { + case IIO_BLOCK_STATE_DEQUEUED: + case IIO_BLOCK_STATE_QUEUED: + case IIO_BLOCK_STATE_DONE: + return true; + default: + return false; + } +} + +/** + * iio_dma_buffer_request_update() - DMA buffer request_update callback + * @buffer: The buffer which to request an update + * + * Should be used as the iio_dma_buffer_request_update() callback for + * iio_buffer_access_ops struct for DMA buffers. + */ +int iio_dma_buffer_request_update(struct iio_buffer *buffer) +{ + struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer); + struct iio_dma_buffer_block *block; + bool try_reuse = false; + size_t size; + int ret = 0; + int i; + + /* + * Split the buffer into two even parts. This is used as a double + * buffering scheme with usually one block at a time being used by the + * DMA and the other one by the application. + */ + size = DIV_ROUND_UP(queue->buffer.bytes_per_datum * + queue->buffer.length, 2); + + mutex_lock(&queue->lock); + + /* Allocations are page aligned */ + if (PAGE_ALIGN(queue->fileio.block_size) == PAGE_ALIGN(size)) + try_reuse = true; + + queue->fileio.block_size = size; + queue->fileio.active_block = NULL; + + spin_lock_irq(&queue->list_lock); + for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) { + block = queue->fileio.blocks[i]; + + /* If we can't re-use it free it */ + if (block && (!iio_dma_block_reusable(block) || !try_reuse)) + block->state = IIO_BLOCK_STATE_DEAD; + } + + /* + * At this point all blocks are either owned by the core or marked as + * dead. This means we can reset the lists without having to fear + * corrution. + */ + INIT_LIST_HEAD(&queue->outgoing); + spin_unlock_irq(&queue->list_lock); + + INIT_LIST_HEAD(&queue->incoming); + + for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) { + if (queue->fileio.blocks[i]) { + block = queue->fileio.blocks[i]; + if (block->state == IIO_BLOCK_STATE_DEAD) { + /* Could not reuse it */ + iio_buffer_block_put(block); + block = NULL; + } else { + block->size = size; + } + } else { + block = NULL; + } + + if (!block) { + block = iio_dma_buffer_alloc_block(queue, size); + if (!block) { + ret = -ENOMEM; + goto out_unlock; + } + queue->fileio.blocks[i] = block; + } + + block->state = IIO_BLOCK_STATE_QUEUED; + list_add_tail(&block->head, &queue->incoming); + } + +out_unlock: + mutex_unlock(&queue->lock); + + return ret; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_request_update); + +static void iio_dma_buffer_submit_block(struct iio_dma_buffer_queue *queue, + struct iio_dma_buffer_block *block) +{ + int ret; + + /* + * If the hardware has already been removed we put the block into + * limbo. It will neither be on the incoming nor outgoing list, nor will + * it ever complete. It will just wait to be freed eventually. + */ + if (!queue->ops) + return; + + block->state = IIO_BLOCK_STATE_ACTIVE; + iio_buffer_block_get(block); + ret = queue->ops->submit(queue, block); + if (ret) { + /* + * This is a bit of a problem and there is not much we can do + * other then wait for the buffer to be disabled and re-enabled + * and try again. But it should not really happen unless we run + * out of memory or something similar. + * + * TODO: Implement support in the IIO core to allow buffers to + * notify consumers that something went wrong and the buffer + * should be disabled. + */ + iio_buffer_block_put(block); + } +} + +/** + * iio_dma_buffer_enable() - Enable DMA buffer + * @buffer: IIO buffer to enable + * @indio_dev: IIO device the buffer is attached to + * + * Needs to be called when the device that the buffer is attached to starts + * sampling. Typically should be the iio_buffer_access_ops enable callback. + * + * This will allocate the DMA buffers and start the DMA transfers. + */ +int iio_dma_buffer_enable(struct iio_buffer *buffer, + struct iio_dev *indio_dev) +{ + struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer); + struct iio_dma_buffer_block *block, *_block; + + mutex_lock(&queue->lock); + queue->active = true; + list_for_each_entry_safe(block, _block, &queue->incoming, head) { + list_del(&block->head); + iio_dma_buffer_submit_block(queue, block); + } + mutex_unlock(&queue->lock); + + return 0; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_enable); + +/** + * iio_dma_buffer_disable() - Disable DMA buffer + * @buffer: IIO DMA buffer to disable + * @indio_dev: IIO device the buffer is attached to + * + * Needs to be called when the device that the buffer is attached to stops + * sampling. Typically should be the iio_buffer_access_ops disable callback. + */ +int iio_dma_buffer_disable(struct iio_buffer *buffer, + struct iio_dev *indio_dev) +{ + struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer); + + mutex_lock(&queue->lock); + queue->active = false; + + if (queue->ops && queue->ops->abort) + queue->ops->abort(queue); + mutex_unlock(&queue->lock); + + return 0; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_disable); + +static void iio_dma_buffer_enqueue(struct iio_dma_buffer_queue *queue, + struct iio_dma_buffer_block *block) +{ + if (block->state == IIO_BLOCK_STATE_DEAD) { + iio_buffer_block_put(block); + } else if (queue->active) { + iio_dma_buffer_submit_block(queue, block); + } else { + block->state = IIO_BLOCK_STATE_QUEUED; + list_add_tail(&block->head, &queue->incoming); + } +} + +static struct iio_dma_buffer_block *iio_dma_buffer_dequeue( + struct iio_dma_buffer_queue *queue) +{ + struct iio_dma_buffer_block *block; + + spin_lock_irq(&queue->list_lock); + block = list_first_entry_or_null(&queue->outgoing, struct + iio_dma_buffer_block, head); + if (block != NULL) { + list_del(&block->head); + block->state = IIO_BLOCK_STATE_DEQUEUED; + } + spin_unlock_irq(&queue->list_lock); + + return block; +} + +/** + * iio_dma_buffer_read() - DMA buffer read callback + * @buffer: Buffer to read form + * @n: Number of bytes to read + * @user_buffer: Userspace buffer to copy the data to + * + * Should be used as the read_first_n callback for iio_buffer_access_ops + * struct for DMA buffers. + */ +int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n, + char __user *user_buffer) +{ + struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer); + struct iio_dma_buffer_block *block; + int ret; + + if (n < buffer->bytes_per_datum) + return -EINVAL; + + mutex_lock(&queue->lock); + + if (!queue->fileio.active_block) { + block = iio_dma_buffer_dequeue(queue); + if (block == NULL) { + ret = 0; + goto out_unlock; + } + queue->fileio.pos = 0; + queue->fileio.active_block = block; + } else { + block = queue->fileio.active_block; + } + + n = rounddown(n, buffer->bytes_per_datum); + if (n > block->bytes_used - queue->fileio.pos) + n = block->bytes_used - queue->fileio.pos; + + if (copy_to_user(user_buffer, block->vaddr + queue->fileio.pos, n)) { + ret = -EFAULT; + goto out_unlock; + } + + queue->fileio.pos += n; + + if (queue->fileio.pos == block->bytes_used) { + queue->fileio.active_block = NULL; + iio_dma_buffer_enqueue(queue, block); + } + + ret = n; + +out_unlock: + mutex_unlock(&queue->lock); + + return ret; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_read); + +/** + * iio_dma_buffer_data_available() - DMA buffer data_available callback + * @buf: Buffer to check for data availability + * + * Should be used as the data_available callback for iio_buffer_access_ops + * struct for DMA buffers. + */ +size_t iio_dma_buffer_data_available(struct iio_buffer *buf) +{ + struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buf); + struct iio_dma_buffer_block *block; + size_t data_available = 0; + + /* + * For counting the available bytes we'll use the size of the block not + * the number of actual bytes available in the block. Otherwise it is + * possible that we end up with a value that is lower than the watermark + * but won't increase since all blocks are in use. + */ + + mutex_lock(&queue->lock); + if (queue->fileio.active_block) + data_available += queue->fileio.active_block->size; + + spin_lock_irq(&queue->list_lock); + list_for_each_entry(block, &queue->outgoing, head) + data_available += block->size; + spin_unlock_irq(&queue->list_lock); + mutex_unlock(&queue->lock); + + return data_available; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_data_available); + +/** + * iio_dma_buffer_set_bytes_per_datum() - DMA buffer set_bytes_per_datum callback + * @buffer: Buffer to set the bytes-per-datum for + * @bpd: The new bytes-per-datum value + * + * Should be used as the set_bytes_per_datum callback for iio_buffer_access_ops + * struct for DMA buffers. + */ +int iio_dma_buffer_set_bytes_per_datum(struct iio_buffer *buffer, size_t bpd) +{ + buffer->bytes_per_datum = bpd; + + return 0; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_set_bytes_per_datum); + +/** + * iio_dma_buffer_set_length - DMA buffer set_length callback + * @buffer: Buffer to set the length for + * @length: The new buffer length + * + * Should be used as the set_length callback for iio_buffer_access_ops + * struct for DMA buffers. + */ +int iio_dma_buffer_set_length(struct iio_buffer *buffer, unsigned int length) +{ + /* Avoid an invalid state */ + if (length < 2) + length = 2; + buffer->length = length; + buffer->watermark = length / 2; + + return 0; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_set_length); + +/** + * iio_dma_buffer_init() - Initialize DMA buffer queue + * @queue: Buffer to initialize + * @dev: DMA device + * @ops: DMA buffer queue callback operations + * + * The DMA device will be used by the queue to do DMA memory allocations. So it + * should refer to the device that will perform the DMA to ensure that + * allocations are done from a memory region that can be accessed by the device. + */ +int iio_dma_buffer_init(struct iio_dma_buffer_queue *queue, + struct device *dev, const struct iio_dma_buffer_ops *ops) +{ + iio_buffer_init(&queue->buffer); + queue->buffer.length = PAGE_SIZE; + queue->buffer.watermark = queue->buffer.length / 2; + queue->dev = dev; + queue->ops = ops; + + INIT_LIST_HEAD(&queue->incoming); + INIT_LIST_HEAD(&queue->outgoing); + + mutex_init(&queue->lock); + spin_lock_init(&queue->list_lock); + + return 0; +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_init); + +/** + * iio_dma_buffer_exit() - Cleanup DMA buffer queue + * @queue: Buffer to cleanup + * + * After this function has completed it is safe to free any resources that are + * associated with the buffer and are accessed inside the callback operations. + */ +void iio_dma_buffer_exit(struct iio_dma_buffer_queue *queue) +{ + unsigned int i; + + mutex_lock(&queue->lock); + + spin_lock_irq(&queue->list_lock); + for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) { + if (!queue->fileio.blocks[i]) + continue; + queue->fileio.blocks[i]->state = IIO_BLOCK_STATE_DEAD; + } + INIT_LIST_HEAD(&queue->outgoing); + spin_unlock_irq(&queue->list_lock); + + INIT_LIST_HEAD(&queue->incoming); + + for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) { + if (!queue->fileio.blocks[i]) + continue; + iio_buffer_block_put(queue->fileio.blocks[i]); + queue->fileio.blocks[i] = NULL; + } + queue->fileio.active_block = NULL; + queue->ops = NULL; + + mutex_unlock(&queue->lock); +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_exit); + +/** + * iio_dma_buffer_release() - Release final buffer resources + * @queue: Buffer to release + * + * Frees resources that can't yet be freed in iio_dma_buffer_exit(). Should be + * called in the buffers release callback implementation right before freeing + * the memory associated with the buffer. + */ +void iio_dma_buffer_release(struct iio_dma_buffer_queue *queue) +{ + mutex_destroy(&queue->lock); +} +EXPORT_SYMBOL_GPL(iio_dma_buffer_release); + +MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>"); +MODULE_DESCRIPTION("DMA buffer for the IIO framework"); +MODULE_LICENSE("GPL v2"); |