Commit b012186a authored by Kieran Bingham's avatar Kieran Bingham Committed by Mauro Carvalho Chehab
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media: uvcvideo: Move decode processing to process context 



Newer high definition cameras, and cameras with multiple lenses such as
the range of stereo-vision cameras now available have ever increasing
data rates.

The inclusion of a variable length packet header in URB packets mean
that we must memcpy the frame data out to our destination 'manually'.
This can result in data rates of up to 2 gigabits per second being
processed.

To improve efficiency, and maximise throughput, handle the URB decode
processing through a work queue to move it from interrupt context, and
allow multiple processors to work on URBs in parallel.

Signed-off-by: default avatarKieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
parent ece41454

drivers/media/usb/uvc/uvc_driver.c

+11 −0
Original line number Diff line number Diff line
@@ -401,6 +401,9 @@ static struct uvc_streaming *uvc_stream_by_id(struct uvc_device *dev, int id) 


static void uvc_stream_delete(struct uvc_streaming *stream)

{

	if (stream->async_wq)

		destroy_workqueue(stream->async_wq);



	mutex_destroy(&stream->mutex);



	usb_put_intf(stream->intf);
@@ -425,6 +428,14 @@ static struct uvc_streaming *uvc_stream_new(struct uvc_device *dev, 
	stream->intf = usb_get_intf(intf);

	stream->intfnum = intf->cur_altsetting->desc.bInterfaceNumber;



	/* Allocate a stream specific work queue for asynchronous tasks. */

	stream->async_wq = alloc_workqueue("uvcvideo", WQ_UNBOUND | WQ_HIGHPRI,

					   0);

	if (!stream->async_wq) {

		uvc_stream_delete(stream);

		return NULL;

	}



	return stream;

}

drivers/media/usb/uvc/uvc_video.c

+80 −24
Original line number Diff line number Diff line
@@ -1094,21 +1094,54 @@ static int uvc_video_decode_start(struct uvc_streaming *stream, 
	return data[0];

}



static void uvc_video_decode_data(struct uvc_streaming *stream,

/*

 * uvc_video_decode_data_work: Asynchronous memcpy processing

 *

 * Copy URB data to video buffers in process context, releasing buffer

 * references and requeuing the URB when done.

 */

static void uvc_video_copy_data_work(struct work_struct *work)

{

	struct uvc_urb *uvc_urb = container_of(work, struct uvc_urb, work);

	unsigned int i;

	int ret;



	for (i = 0; i < uvc_urb->async_operations; i++) {

		struct uvc_copy_op *op = &uvc_urb->copy_operations[i];



		memcpy(op->dst, op->src, op->len);



		/* Release reference taken on this buffer. */

		uvc_queue_buffer_release(op->buf);

	}



	ret = usb_submit_urb(uvc_urb->urb, GFP_KERNEL);

	if (ret < 0)

		uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",

			   ret);

}



static void uvc_video_decode_data(struct uvc_urb *uvc_urb,

		struct uvc_buffer *buf, const u8 *data, int len)

{

	unsigned int maxlen, nbytes;

	void *mem;

	unsigned int active_op = uvc_urb->async_operations;

	struct uvc_copy_op *op = &uvc_urb->copy_operations[active_op];

	unsigned int maxlen;



	if (len <= 0)

		return;



	/* Copy the video data to the buffer. */

	maxlen = buf->length - buf->bytesused;

	mem = buf->mem + buf->bytesused;

	nbytes = min((unsigned int)len, maxlen);

	memcpy(mem, data, nbytes);

	buf->bytesused += nbytes;



	/* Take a buffer reference for async work. */

	kref_get(&buf->ref);



	op->buf = buf;

	op->src = data;

	op->dst = buf->mem + buf->bytesused;

	op->len = min_t(unsigned int, len, maxlen);



	buf->bytesused += op->len;



	/* Complete the current frame if the buffer size was exceeded. */

	if (len > maxlen) {
@@ -1116,6 +1149,8 @@ static void uvc_video_decode_data(struct uvc_streaming *stream, 
		buf->error = 1;

		buf->state = UVC_BUF_STATE_READY;

	}



	uvc_urb->async_operations++;

}



static void uvc_video_decode_end(struct uvc_streaming *stream,
@@ -1324,7 +1359,7 @@ static void uvc_video_decode_isoc(struct uvc_urb *uvc_urb, 
		uvc_video_decode_meta(stream, meta_buf, mem, ret);



		/* Decode the payload data. */

		uvc_video_decode_data(stream, buf, mem + ret,

		uvc_video_decode_data(uvc_urb, buf, mem + ret,

			urb->iso_frame_desc[i].actual_length - ret);



		/* Process the header again. */
@@ -1384,9 +1419,9 @@ static void uvc_video_decode_bulk(struct uvc_urb *uvc_urb, 
	 * sure buf is never dereferenced if NULL.

	 */



	/* Process video data. */

	/* Prepare video data for processing. */

	if (!stream->bulk.skip_payload && buf != NULL)

		uvc_video_decode_data(stream, buf, mem, len);

		uvc_video_decode_data(uvc_urb, buf, mem, len);



	/* Detect the payload end by a URB smaller than the maximum size (or

	 * a payload size equal to the maximum) and process the header again.
@@ -1472,7 +1507,7 @@ static void uvc_video_complete(struct urb *urb) 
		uvc_printk(KERN_WARNING, "Non-zero status (%d) in video "

			"completion handler.\n", urb->status);

		/* fall through */

	case -ENOENT:		/* usb_kill_urb() called. */

	case -ENOENT:		/* usb_poison_urb() called. */

		if (stream->frozen)

			return;

		/* fall through */
@@ -1494,12 +1529,26 @@ static void uvc_video_complete(struct urb *urb) 
		spin_unlock_irqrestore(&qmeta->irqlock, flags);

	}



	/* Re-initialise the URB async work. */

	uvc_urb->async_operations = 0;



	/*

	 * Process the URB headers, and optionally queue expensive memcpy tasks

	 * to be deferred to a work queue.

	 */

	stream->decode(uvc_urb, buf, buf_meta);



	if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {

		uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",

	/* If no async work is needed, resubmit the URB immediately. */

	if (!uvc_urb->async_operations) {

		ret = usb_submit_urb(uvc_urb->urb, GFP_ATOMIC);

		if (ret < 0)

			uvc_printk(KERN_ERR,

				   "Failed to resubmit video URB (%d).\n",

				   ret);

		return;

	}



	queue_work(stream->async_wq, &uvc_urb->work);

}



/*
@@ -1594,20 +1643,22 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream, 
 */

static void uvc_uninit_video(struct uvc_streaming *stream, int free_buffers)

{

	struct urb *urb;

	unsigned int i;

	struct uvc_urb *uvc_urb;



	uvc_video_stats_stop(stream);



	for (i = 0; i < UVC_URBS; ++i) {

		struct uvc_urb *uvc_urb = &stream->uvc_urb[i];

	/*

	 * We must poison the URBs rather than kill them to ensure that even

	 * after the completion handler returns, any asynchronous workqueues

	 * will be prevented from resubmitting the URBs.

	 */

	for_each_uvc_urb(uvc_urb, stream)

		usb_poison_urb(uvc_urb->urb);



		urb = uvc_urb->urb;

		if (urb == NULL)

			continue;

	flush_workqueue(stream->async_wq);



		usb_kill_urb(urb);

		usb_free_urb(urb);

	for_each_uvc_urb(uvc_urb, stream) {

		usb_free_urb(uvc_urb->urb);

		uvc_urb->urb = NULL;

	}
@@ -1932,6 +1983,7 @@ int uvc_video_init(struct uvc_streaming *stream) 
	struct uvc_streaming_control *probe = &stream->ctrl;

	struct uvc_format *format = NULL;

	struct uvc_frame *frame = NULL;

	struct uvc_urb *uvc_urb;

	unsigned int i;

	int ret;
@@ -2017,6 +2069,10 @@ int uvc_video_init(struct uvc_streaming *stream) 
		}

	}



	/* Prepare asynchronous work items. */

	for_each_uvc_urb(uvc_urb, stream)

		INIT_WORK(&uvc_urb->work, uvc_video_copy_data_work);



	return 0;

}

drivers/media/usb/uvc/uvcvideo.h

+28 −0
Original line number Diff line number Diff line
@@ -493,6 +493,21 @@ struct uvc_stats_stream { 


#define UVC_METATADA_BUF_SIZE 1024



/**

 * struct uvc_copy_op: Context structure to schedule asynchronous memcpy

 *

 * @buf: active buf object for this operation

 * @dst: copy destination address

 * @src: copy source address

 * @len: copy length

 */

struct uvc_copy_op {

	struct uvc_buffer *buf;

	void *dst;

	const __u8 *src;

	size_t len;

};



/**

 * struct uvc_urb - URB context management structure

 *
@@ -500,6 +515,9 @@ struct uvc_stats_stream { 
 * @stream: UVC streaming context

 * @buffer: memory storage for the URB

 * @dma: DMA coherent addressing for the urb_buffer

 * @async_operations: counter to indicate the number of copy operations

 * @copy_operations: work descriptors for asynchronous copy operations

 * @work: work queue entry for asynchronous decode

 */

struct uvc_urb {

	struct urb *urb;
@@ -507,6 +525,10 @@ struct uvc_urb { 


	char *buffer;

	dma_addr_t dma;



	unsigned int async_operations;

	struct uvc_copy_op copy_operations[UVC_MAX_PACKETS];

	struct work_struct work;

};



struct uvc_streaming {
@@ -539,6 +561,7 @@ struct uvc_streaming { 
	/* Buffers queue. */

	unsigned int frozen : 1;

	struct uvc_video_queue queue;

	struct workqueue_struct *async_wq;

	void (*decode)(struct uvc_urb *uvc_urb, struct uvc_buffer *buf,

		       struct uvc_buffer *meta_buf);
@@ -592,6 +615,11 @@ struct uvc_streaming { 
	} clock;

};



#define for_each_uvc_urb(uvc_urb, uvc_streaming) \

	for ((uvc_urb) = &(uvc_streaming)->uvc_urb[0]; \

	     (uvc_urb) < &(uvc_streaming)->uvc_urb[UVC_URBS]; \

	     ++(uvc_urb))



struct uvc_device_info {

	u32	quirks;

	u32	meta_format;

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