Release 4.11 drivers/iio/buffer/industrialio-buffer-dma.c
/*
* 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-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);
}
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static void iio_buffer_block_get(struct iio_dma_buffer_block *block)
{
kref_get(&block->kref);
}
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static void iio_buffer_block_put(struct iio_dma_buffer_block *block)
{
kref_put(&block->kref, iio_buffer_block_release);
}
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/*
* 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);
}
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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);
}
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/*
* 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);
}
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static struct iio_dma_buffer_queue *iio_buffer_to_queue(struct iio_buffer *buf)
{
return container_of(buf, struct iio_dma_buffer_queue, buffer);
}
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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;
}
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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);
}
}
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/**
* 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, POLLIN | POLLRDNORM);
}
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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, POLLIN | POLLRDNORM);
}
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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;
}
}
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/**
* 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;
}
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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);
}
}
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/**
* 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;
}
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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;
}
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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);
}
}
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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;
}
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/**
* 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;
}
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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;
}
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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;
}
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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, int length)
{
/* Avoid an invalid state */
if (length < 2)
length = 2;
buffer->length = length;
buffer->watermark = length / 2;
return 0;
}
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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;
}
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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);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Lars-Peter Clausen | 182 | 100.00% | 1 | 100.00% |
| Total | 182 | 100.00% | 1 | 100.00% |
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);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Lars-Peter Clausen | 18 | 100.00% | 1 | 100.00% |
| Total | 18 | 100.00% | 1 | 100.00% |
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");
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Lars-Peter Clausen | 2203 | 99.28% | 1 | 50.00% |
| Phil Reid | 16 | 0.72% | 1 | 50.00% |
| Total | 2219 | 100.00% | 2 | 100.00% |
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