Re: [PATCH 01/15] iio: buffer-dma: Get rid of incoming/outgoing queues

From: Alexandru Ardelean
Date: Tue Nov 16 2021 - 03:23:35 EST

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On Mon, Nov 15, 2021 at 4:19 PM Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
>
> The buffer-dma code was using two queues, incoming and outgoing, to
> manage the state of the blocks in use.
>
> While this totally works, it adds some complexity to the code,
> especially since the code only manages 2 blocks. It is much easier to
> just check each block's state manually, and keep a counter for the next
> block to dequeue.
>
> Since the new DMABUF based API wouldn't use these incoming and outgoing
> queues anyway, getting rid of them now makes the upcoming changes
> simpler.
>

Reviewed-by: Alexandru Ardelean <ardeleanalex@xxxxxxxxx>

> Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> ---
> drivers/iio/buffer/industrialio-buffer-dma.c | 68 ++++++++++----------
> include/linux/iio/buffer-dma.h | 7 +-
> 2 files changed, 37 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
> index d348af8b9705..abac88f20104 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dma.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dma.c
> @@ -191,16 +191,8 @@ static struct iio_dma_buffer_block *iio_dma_buffer_alloc_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) {
> + if (block->state != IIO_BLOCK_STATE_DEAD)
> block->state = IIO_BLOCK_STATE_DONE;
> - list_add_tail(&block->head, &queue->outgoing);
> - }
> }
>
> /**
> @@ -317,11 +309,8 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
> * 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];
> @@ -346,7 +335,6 @@ int iio_dma_buffer_request_update(struct iio_buffer *buffer)
> }
>
> block->state = IIO_BLOCK_STATE_QUEUED;
> - list_add_tail(&block->head, &queue->incoming);
> }
>
> out_unlock:
> @@ -401,13 +389,18 @@ 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;
> + struct iio_dma_buffer_block *block;
> + unsigned int i;
>
> 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);
> + queue->fileio.next_dequeue = 0;
> +
> + for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) {
> + block = queue->fileio.blocks[i];
> +
> + if (block->state == IIO_BLOCK_STATE_QUEUED)
> + iio_dma_buffer_submit_block(queue, block);
> }
> mutex_unlock(&queue->lock);
>
> @@ -442,28 +435,33 @@ 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) {
> + if (block->state == IIO_BLOCK_STATE_DEAD)
> iio_buffer_block_put(block);
> - } else if (queue->active) {
> + else if (queue->active)
> iio_dma_buffer_submit_block(queue, block);
> - } else {
> + 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;
> + unsigned int idx;
>
> 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);
> +
> + idx = queue->fileio.next_dequeue;
> + block = queue->fileio.blocks[idx];
> +
> + if (block->state == IIO_BLOCK_STATE_DONE) {
> block->state = IIO_BLOCK_STATE_DEQUEUED;
> + idx = (idx + 1) % ARRAY_SIZE(queue->fileio.blocks);
> + queue->fileio.next_dequeue = idx;
> + } else {
> + block = NULL;
> }
> +
> spin_unlock_irq(&queue->list_lock);
>
> return block;
> @@ -539,6 +537,7 @@ 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;
> + unsigned int i;
>
> /*
> * For counting the available bytes we'll use the size of the block not
> @@ -552,8 +551,15 @@ size_t iio_dma_buffer_data_available(struct iio_buffer *buf)
> 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;
> +
> + for (i = 0; i < ARRAY_SIZE(queue->fileio.blocks); i++) {
> + block = queue->fileio.blocks[i];
> +
> + if (block != queue->fileio.active_block
> + && block->state == IIO_BLOCK_STATE_DONE)
> + data_available += block->size;
> + }
> +
> spin_unlock_irq(&queue->list_lock);
> mutex_unlock(&queue->lock);
>
> @@ -616,9 +622,6 @@ int iio_dma_buffer_init(struct iio_dma_buffer_queue *queue,
> 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);
>
> @@ -645,11 +648,8 @@ void iio_dma_buffer_exit(struct iio_dma_buffer_queue *queue)
> 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;
> diff --git a/include/linux/iio/buffer-dma.h b/include/linux/iio/buffer-dma.h
> index ff15c61bf319..d4ed5ff39d44 100644
> --- a/include/linux/iio/buffer-dma.h
> +++ b/include/linux/iio/buffer-dma.h
> @@ -78,12 +78,15 @@ 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
> + * @next_dequeue: index of next block that will be dequeued
> */
> 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;
> +
> + unsigned int next_dequeue;
> };
>
> /**
> @@ -97,8 +100,6 @@ struct iio_dma_buffer_queue_fileio {
> * atomic context as well as blocks on those lists. This is the outgoing queue
> * list and typically also a list of active blocks in the part that handles
> * the DMA controller
> - * @incoming: List of buffers on the incoming queue
> - * @outgoing: List of buffers on the outgoing queue
> * @active: Whether the buffer is currently active
> * @fileio: FileIO state
> */
> @@ -109,8 +110,6 @@ struct iio_dma_buffer_queue {
>
> struct mutex lock;
> spinlock_t list_lock;
> - struct list_head incoming;
> - struct list_head outgoing;
>
> bool active;
>
> --
> 2.33.0
>

Next message: Heikki Krogerus: "Re: [RFC PATCH v4 net-next 15/23] device property: add helper function fwnode_get_child_node_count"
Previous message: Alexandru Ardelean: "Re: [PATCH 02/15] iio: buffer-dma: Remove unused iio_buffer_block struct"
Next in thread: Jonathan Cameron: "Re: [PATCH 01/15] iio: buffer-dma: Get rid of incoming/outgoing queues"
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