[PATCH v2 2/3] iio: buffer-dma: Add mmap support

[Alexandru Ardelean <alexandru.ardelean@analog.com>]

From: Lars-Peter Clausen <lars@metafoo.de>

Add support for the new mmap interface to IIO DMA buffer. This interface
allows to directly map the backing memory of a block to userspace. This is
especially advantageous for high-speed devices where the extra copy from
kernel space to userspace of the data incurs a significant overhead.

In addition this interface allows more fine grained control over how many
blocks are allocated and their size.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/iio/buffer/industrialio-buffer-dma.c  | 314 ++++++++++++++++--
 .../buffer/industrialio-buffer-dmaengine.c    |  22 +-
 drivers/iio/industrialio-buffer.c             |   1 +
 include/linux/iio/buffer-dma.h                |  20 +-
 4 files changed, 321 insertions(+), 36 deletions(-)

diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
index d348af8b9705..befb0a3d2def 100644
--- a/drivers/iio/buffer/industrialio-buffer-dma.c
+++ b/drivers/iio/buffer/industrialio-buffer-dma.c
@@ -90,6 +90,9 @@
  * callback is called from within the custom callback.
  */
 
+static unsigned int iio_dma_buffer_max_block_size = SZ_16M;
+module_param_named(max_block_size, iio_dma_buffer_max_block_size, uint, 0644);
+
 static void iio_buffer_block_release(struct kref *kref)
 {
 	struct iio_dma_buffer_block *block = container_of(kref,
@@ -97,7 +100,7 @@ static void iio_buffer_block_release(struct kref *kref)
 
 	WARN_ON(block->state != IIO_BLOCK_STATE_DEAD);
 
-	dma_free_coherent(block->queue->dev, PAGE_ALIGN(block->size),
+	dma_free_coherent(block->queue->dev, PAGE_ALIGN(block->block.size),
 					block->vaddr, block->phys_addr);
 
 	iio_buffer_put(&block->queue->buffer);
@@ -178,7 +181,7 @@ static struct iio_dma_buffer_block *iio_dma_buffer_alloc_block(
 		return NULL;
 	}
 
-	block->size = size;
+	block->block.size = size;
 	block->state = IIO_BLOCK_STATE_DEQUEUED;
 	block->queue = queue;
 	INIT_LIST_HEAD(&block->head);
@@ -243,7 +246,7 @@ void iio_dma_buffer_block_list_abort(struct iio_dma_buffer_queue *queue,
 	spin_lock_irqsave(&queue->list_lock, flags);
 	list_for_each_entry_safe(block, _block, list, head) {
 		list_del(&block->head);
-		block->bytes_used = 0;
+		block->block.bytes_used = 0;
 		_iio_dma_buffer_block_done(block);
 		iio_buffer_block_put_atomic(block);
 	}
@@ -296,6 +299,10 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
 
 	mutex_lock(&queue->lock);
 
+	/* If in mmap mode dont do anything */
+	if (queue->num_blocks)
+		goto out_unlock;
+
 	/* Allocations are page aligned */
 	if (PAGE_ALIGN(queue->fileio.block_size) == PAGE_ALIGN(size))
 		try_reuse = true;
@@ -330,7 +337,7 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
 				iio_buffer_block_put(block);
 				block = NULL;
 			} else {
-				block->size = size;
+				block->block.size = size;
 			}
 		} else {
 			block = NULL;
@@ -345,6 +352,8 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
 			queue->fileio.blocks[i] = block;
 		}
 
+		block->block.id = i;
+
 		block->state = IIO_BLOCK_STATE_QUEUED;
 		list_add_tail(&block->head, &queue->incoming);
 	}
@@ -356,6 +365,30 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
 }
 EXPORT_SYMBOL_GPL(iio_dma_buffer_request_update);
 
+static void iio_dma_buffer_fileio_free(struct iio_dma_buffer_queue *queue)
+{
+	unsigned int i;
+
+	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;
+}
+
 static void iio_dma_buffer_submit_block(struct iio_dma_buffer_queue *queue,
 	struct iio_dma_buffer_block *block)
 {
@@ -404,6 +437,7 @@ int iio_dma_buffer_enable(struct iio_buffer *buffer,
 	struct iio_dma_buffer_block *block, *_block;
 
 	mutex_lock(&queue->lock);
+	queue->fileio.enabled = !queue->num_blocks;
 	queue->active = true;
 	list_for_each_entry_safe(block, _block, &queue->incoming, head) {
 		list_del(&block->head);
@@ -429,6 +463,7 @@ int iio_dma_buffer_disable(struct iio_buffer *buffer,
 	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
 
 	mutex_lock(&queue->lock);
+	queue->fileio.enabled = false;
 	queue->active = false;
 
 	if (queue->ops && queue->ops->abort)
@@ -490,6 +525,11 @@ int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
 
 	mutex_lock(&queue->lock);
 
+	if (!queue->fileio.enabled) {
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
 	if (!queue->fileio.active_block) {
 		block = iio_dma_buffer_dequeue(queue);
 		if (block == NULL) {
@@ -503,8 +543,8 @@ int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
 	}
 
 	n = rounddown(n, buffer->bytes_per_datum);
-	if (n > block->bytes_used - queue->fileio.pos)
-		n = block->bytes_used - queue->fileio.pos;
+	if (n > block->block.bytes_used - queue->fileio.pos)
+		n = block->block.bytes_used - queue->fileio.pos;
 
 	if (copy_to_user(user_buffer, block->vaddr + queue->fileio.pos, n)) {
 		ret = -EFAULT;
@@ -513,7 +553,7 @@ int iio_dma_buffer_read(struct iio_buffer *buffer, size_t n,
 
 	queue->fileio.pos += n;
 
-	if (queue->fileio.pos == block->bytes_used) {
+	if (queue->fileio.pos == block->block.bytes_used) {
 		queue->fileio.active_block = NULL;
 		iio_dma_buffer_enqueue(queue, block);
 	}
@@ -549,11 +589,11 @@ size_t iio_dma_buffer_data_available(struct iio_buffer *buf)
 
 	mutex_lock(&queue->lock);
 	if (queue->fileio.active_block)
-		data_available += queue->fileio.active_block->size;
+		data_available += queue->fileio.active_block->block.size;
 
 	spin_lock_irq(&queue->list_lock);
 	list_for_each_entry(block, &queue->outgoing, head)
-		data_available += block->size;
+		data_available += block->block.size;
 	spin_unlock_irq(&queue->list_lock);
 	mutex_unlock(&queue->lock);
 
@@ -561,6 +601,241 @@ size_t iio_dma_buffer_data_available(struct iio_buffer *buf)
 }
 EXPORT_SYMBOL_GPL(iio_dma_buffer_data_available);
 
+int iio_dma_buffer_alloc_blocks(struct iio_buffer *buffer,
+				struct iio_buffer_block_alloc_req *req)
+{
+	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
+	struct iio_dma_buffer_block **blocks;
+	unsigned int num_blocks;
+	unsigned int i;
+	int ret = 0;
+
+	mutex_lock(&queue->lock);
+
+	/*
+	 * If the buffer is enabled and in fileio mode new blocks can't be
+	 * allocated.
+	 */
+	if (queue->fileio.enabled) {
+		ret = -EBUSY;
+		goto err_unlock;
+	}
+
+	/* Free memory that might be in use for fileio mode */
+	iio_dma_buffer_fileio_free(queue);
+
+	/* 64 blocks ought to be enough for anybody ;) */
+	if (req->count > 64 - queue->num_blocks)
+		req->count = 64 - queue->num_blocks;
+	if (req->size > iio_dma_buffer_max_block_size)
+		req->size = iio_dma_buffer_max_block_size;
+
+	req->id = queue->num_blocks;
+
+	if (req->count == 0 || req->size == 0) {
+		ret = 0;
+		goto err_unlock;
+	}
+
+	num_blocks = req->count + queue->num_blocks;
+
+	blocks = krealloc(queue->blocks, sizeof(*blocks) * num_blocks,
+		GFP_KERNEL);
+	if (!blocks) {
+		ret = -ENOMEM;
+		goto err_unlock;
+	}
+
+	for (i = queue->num_blocks; i < num_blocks; i++) {
+		blocks[i] = iio_dma_buffer_alloc_block(queue, req->size);
+		if (!blocks[i])
+			break;
+		blocks[i]->block.id = i;
+		blocks[i]->block.data.offset = queue->max_offset;
+		queue->max_offset += PAGE_ALIGN(req->size);
+	}
+
+	req->count = i - queue->num_blocks;
+	queue->num_blocks = i;
+	queue->blocks = blocks;
+
+err_unlock:
+	mutex_unlock(&queue->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_dma_buffer_alloc_blocks);
+
+int iio_dma_buffer_free_blocks(struct iio_buffer *buffer)
+{
+	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
+	unsigned int i;
+
+	mutex_lock(&queue->lock);
+
+	spin_lock_irq(&queue->list_lock);
+	INIT_LIST_HEAD(&queue->incoming);
+	INIT_LIST_HEAD(&queue->outgoing);
+
+	for (i = 0; i < queue->num_blocks; i++)
+		queue->blocks[i]->state = IIO_BLOCK_STATE_DEAD;
+	spin_unlock_irq(&queue->list_lock);
+
+	for (i = 0; i < queue->num_blocks; i++)
+		iio_buffer_block_put(queue->blocks[i]);
+
+	kfree(queue->blocks);
+	queue->blocks = NULL;
+	queue->num_blocks = 0;
+	queue->max_offset = 0;
+
+	mutex_unlock(&queue->lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(iio_dma_buffer_free_blocks);
+
+int iio_dma_buffer_query_block(struct iio_buffer *buffer,
+			       struct iio_buffer_block *block)
+{
+	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
+	int ret = 0;
+
+	mutex_lock(&queue->lock);
+
+	if (block->id >= queue->num_blocks) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	*block = queue->blocks[block->id]->block;
+
+out_unlock:
+	mutex_unlock(&queue->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_dma_buffer_query_block);
+
+int iio_dma_buffer_enqueue_block(struct iio_buffer *buffer,
+				 struct iio_buffer_block *block)
+{
+	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
+	struct iio_dma_buffer_block *dma_block;
+	int ret = 0;
+
+	mutex_lock(&queue->lock);
+
+	if (block->id >= queue->num_blocks) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	dma_block = queue->blocks[block->id];
+	dma_block->block.bytes_used = block->bytes_used;
+	dma_block->block.flags = block->flags;
+
+	switch (dma_block->state) {
+	case IIO_BLOCK_STATE_DONE:
+		list_del_init(&dma_block->head);
+		break;
+	case IIO_BLOCK_STATE_QUEUED:
+		/* Nothing to do */
+		goto out_unlock;
+	case IIO_BLOCK_STATE_DEQUEUED:
+		break;
+	default:
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+
+	iio_dma_buffer_enqueue(queue, dma_block);
+
+out_unlock:
+	mutex_unlock(&queue->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_dma_buffer_enqueue_block);
+
+int iio_dma_buffer_dequeue_block(struct iio_buffer *buffer,
+				 struct iio_buffer_block *block)
+{
+	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
+	struct iio_dma_buffer_block *dma_block;
+	int ret = 0;
+
+	mutex_lock(&queue->lock);
+
+	dma_block = iio_dma_buffer_dequeue(queue);
+	if (!dma_block) {
+		ret = -EAGAIN;
+		goto out_unlock;
+	}
+
+	*block = dma_block->block;
+
+out_unlock:
+	mutex_unlock(&queue->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(iio_dma_buffer_dequeue_block);
+
+static void iio_dma_buffer_mmap_open(struct vm_area_struct *area)
+{
+	struct iio_dma_buffer_block *block = area->vm_private_data;
+
+	iio_buffer_block_get(block);
+}
+
+static void iio_dma_buffer_mmap_close(struct vm_area_struct *area)
+{
+	struct iio_dma_buffer_block *block = area->vm_private_data;
+
+	iio_buffer_block_put(block);
+}
+
+static const struct vm_operations_struct iio_dma_buffer_vm_ops = {
+	.open = iio_dma_buffer_mmap_open,
+	.close = iio_dma_buffer_mmap_close,
+};
+
+int iio_dma_buffer_mmap(struct iio_buffer *buffer, struct vm_area_struct *vma)
+{
+	struct iio_dma_buffer_queue *queue = iio_buffer_to_queue(buffer);
+	struct iio_dma_buffer_block *block = NULL;
+	size_t vm_offset;
+	unsigned int i;
+
+	vm_offset = vma->vm_pgoff << PAGE_SHIFT;
+
+	for (i = 0; i < queue->num_blocks; i++) {
+		if (queue->blocks[i]->block.data.offset == vm_offset) {
+			block = queue->blocks[i];
+			break;
+		}
+	}
+
+	if (block == NULL)
+		return -EINVAL;
+
+	if (PAGE_ALIGN(block->block.size) < vma->vm_end - vma->vm_start)
+		return -EINVAL;
+
+	vma->vm_pgoff = 0;
+
+	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+	vma->vm_ops = &iio_dma_buffer_vm_ops;
+	vma->vm_private_data = block;
+
+	vma->vm_ops->open(vma);
+
+	return dma_mmap_coherent(queue->dev, vma, block->vaddr,
+		block->phys_addr, vma->vm_end - vma->vm_start);
+}
+EXPORT_SYMBOL_GPL(iio_dma_buffer_mmap);
+
 /**
  * iio_dma_buffer_set_bytes_per_datum() - DMA buffer set_bytes_per_datum callback
  * @buffer: Buffer to set the bytes-per-datum for
@@ -635,28 +910,9 @@ EXPORT_SYMBOL_GPL(iio_dma_buffer_init);
  */
 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;
+	iio_dma_buffer_fileio_free(queue);
 	queue->ops = NULL;
 
 	mutex_unlock(&queue->lock);
diff --git a/drivers/iio/buffer/industrialio-buffer-dmaengine.c b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
index 8ecdbae83414..bb022922ec23 100644
--- a/drivers/iio/buffer/industrialio-buffer-dmaengine.c
+++ b/drivers/iio/buffer/industrialio-buffer-dmaengine.c
@@ -54,7 +54,7 @@ static void iio_dmaengine_buffer_block_done(void *data,
 	spin_lock_irqsave(&block->queue->list_lock, flags);
 	list_del(&block->head);
 	spin_unlock_irqrestore(&block->queue->list_lock, flags);
-	block->bytes_used -= result->residue;
+	block->block.bytes_used -= result->residue;
 	iio_dma_buffer_block_done(block);
 }
 
@@ -66,12 +66,17 @@ static int iio_dmaengine_buffer_submit_block(struct iio_dma_buffer_queue *queue,
 	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);
+	block->block.bytes_used = min(block->block.size,
+		dmaengine_buffer->max_size);
+	block->block.bytes_used = rounddown(block->block.bytes_used,
+		dmaengine_buffer->align);
+	if (block->block.bytes_used == 0) {
+		iio_dma_buffer_block_done(block);
+		return 0;
+	}
 
 	desc = dmaengine_prep_slave_single(dmaengine_buffer->chan,
-		block->phys_addr, block->bytes_used, DMA_DEV_TO_MEM,
+		block->phys_addr, block->block.bytes_used, DMA_DEV_TO_MEM,
 		DMA_PREP_INTERRUPT);
 	if (!desc)
 		return -ENOMEM;
@@ -120,6 +125,13 @@ static const struct iio_buffer_access_funcs iio_dmaengine_buffer_ops = {
 	.data_available = iio_dma_buffer_data_available,
 	.release = iio_dmaengine_buffer_release,
 
+	.alloc_blocks = iio_dma_buffer_alloc_blocks,
+	.free_blocks = iio_dma_buffer_free_blocks,
+	.query_block = iio_dma_buffer_query_block,
+	.enqueue_block = iio_dma_buffer_enqueue_block,
+	.dequeue_block = iio_dma_buffer_dequeue_block,
+	.mmap = iio_dma_buffer_mmap,
+
 	.modes = INDIO_BUFFER_HARDWARE,
 	.flags = INDIO_BUFFER_FLAG_FIXED_WATERMARK,
 };
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 50228df0b09f..a0d1ad86022f 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -19,6 +19,7 @@
 #include <linux/mm.h>
 #include <linux/poll.h>
 #include <linux/sched/signal.h>
+#include <linux/mm.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/iio-opaque.h>
diff --git a/include/linux/iio/buffer-dma.h b/include/linux/iio/buffer-dma.h
index 6564bdcdac66..315a8d750986 100644
--- a/include/linux/iio/buffer-dma.h
+++ b/include/linux/iio/buffer-dma.h
@@ -47,7 +47,7 @@ enum iio_block_state {
 struct iio_dma_buffer_block {
 	/* May only be accessed by the owner of the block */
 	struct list_head head;
-	size_t bytes_used;
+	struct iio_buffer_block block;
 
 	/*
 	 * Set during allocation, constant thereafter. May be accessed read-only
@@ -55,7 +55,6 @@ struct iio_dma_buffer_block {
 	 */
 	void *vaddr;
 	dma_addr_t phys_addr;
-	size_t size;
 	struct iio_dma_buffer_queue *queue;
 
 	/* Must not be accessed outside the core. */
@@ -73,12 +72,14 @@ struct iio_dma_buffer_block {
  * @active_block: Block being used in read()
  * @pos: Read offset in the active block
  * @block_size: Size of each block
+ * @enabled: Whether the buffer is operating in fileio mode
  */
 struct iio_dma_buffer_queue_fileio {
 	struct iio_dma_buffer_block *blocks[2];
 	struct iio_dma_buffer_block *active_block;
 	size_t pos;
 	size_t block_size;
+	bool enabled;
 };
 
 /**
@@ -109,6 +110,10 @@ struct iio_dma_buffer_queue {
 
 	bool active;
 
+	unsigned int num_blocks;
+	struct iio_dma_buffer_block **blocks;
+	unsigned int max_offset;
+
 	struct iio_dma_buffer_queue_fileio fileio;
 };
 
@@ -143,4 +148,15 @@ int iio_dma_buffer_init(struct iio_dma_buffer_queue *queue,
 void iio_dma_buffer_exit(struct iio_dma_buffer_queue *queue);
 void iio_dma_buffer_release(struct iio_dma_buffer_queue *queue);
 
+int iio_dma_buffer_alloc_blocks(struct iio_buffer *buffer,
+				struct iio_buffer_block_alloc_req *req);
+int iio_dma_buffer_free_blocks(struct iio_buffer *buffer);
+int iio_dma_buffer_query_block(struct iio_buffer *buffer,
+			       struct iio_buffer_block *block);
+int iio_dma_buffer_enqueue_block(struct iio_buffer *buffer,
+				 struct iio_buffer_block *block);
+int iio_dma_buffer_dequeue_block(struct iio_buffer *buffer,
+				 struct iio_buffer_block *block);
+int iio_dma_buffer_mmap(struct iio_buffer *buffer, struct vm_area_struct *vma);
+
 #endif
-- 
2.17.1