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Commit 1b3fd2d3 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[media] em28xx-audio: don't hardcode audio URB calculus 



The current code hardcodes the number of audio URBs, the number
of packets per URB and the maximum URB size.

This is not a good idea, as it:

- wastes more bandwidth than necessary, by using a very
  large number of packets;

- those constants are bound to an specific scenario, with
  a bandwidth of 48 kHz;

- don't take the maximum endpoint size into account;

- with urb->interval = 1 on xHCI, those constraints cause a "funny"
  setup: URBs with 64 packets inside, with only 24 bytes total. E. g.
  a complete waste of space.

Change the code to do dynamic URB audio calculus and allocation.

For now, use the same constraints as used before this patch, to
avoid regressions.

A good scenario (tested) seems to use those defines, instead:

	#define EM28XX_MAX_AUDIO_BUFS          8
	#define EM28XX_MIN_AUDIO_PACKETS       2

But let's not do such change here, letting the optimization to
happen on latter patches, after more tests.

Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 439c491c

drivers/media/usb/em28xx/em28xx-audio.c

+108 −33
Original line number Diff line number Diff line
@@ -50,6 +50,8 @@ static int debug; 
module_param(debug, int, 0644);

MODULE_PARM_DESC(debug, "activates debug info");



#define EM28XX_MAX_AUDIO_BUFS		5

#define EM28XX_MIN_AUDIO_PACKETS	64

#define dprintk(fmt, arg...) do {					\

	    if (debug)							\

		printk(KERN_INFO "em28xx-audio %s: " fmt,		\
@@ -63,7 +65,7 @@ static int em28xx_deinit_isoc_audio(struct em28xx *dev) 
	int i;



	dprintk("Stopping isoc\n");

	for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {

	for (i = 0; i < dev->adev.num_urb; i++) {

		struct urb *urb = dev->adev.urb[i];



		if (!irqs_disabled())
@@ -168,7 +170,7 @@ static int em28xx_init_audio_isoc(struct em28xx *dev) 
	dprintk("Starting isoc transfers\n");



	/* Start streaming */

	for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {

	for (i = 0; i < dev->adev.num_urb; i++) {

		memset(dev->adev.transfer_buffer[i], 0x80,

		       dev->adev.urb[i]->transfer_buffer_length);
@@ -598,21 +600,35 @@ static void em28xx_audio_free_urb(struct em28xx *dev) 
{

	int i;



	for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {

	for (i = 0; i < dev->adev.num_urb; i++) {

		struct urb *urb = dev->adev.urb[i];



		if (!dev->adev.urb[i])

		if (!urb)

			continue;



		if (dev->adev.transfer_buffer[i])

			usb_free_coherent(dev->udev,

					  urb->transfer_buffer_length,

					  dev->adev.transfer_buffer[i],

					  urb->transfer_dma);



		usb_free_urb(urb);

		dev->adev.urb[i] = NULL;

		dev->adev.transfer_buffer[i] = NULL;

	}

	kfree(dev->adev.urb);

	kfree(dev->adev.transfer_buffer);

	dev->adev.num_urb = 0;

}



/* high bandwidth multiplier, as encoded in highspeed endpoint descriptors */

static int em28xx_audio_ep_packet_size(struct usb_device *udev,

					struct usb_endpoint_descriptor *e)

{

	int size = le16_to_cpu(e->wMaxPacketSize);



	if (udev->speed == USB_SPEED_HIGH)

		return (size & 0x7ff) *  (1 + (((size) >> 11) & 0x03));



	return size & 0x7ff;

}



static int em28xx_audio_init(struct em28xx *dev)
@@ -623,9 +639,8 @@ static int em28xx_audio_init(struct em28xx *dev) 
	struct usb_interface *intf;

	struct usb_endpoint_descriptor *e, *ep = NULL;

	static int          devnr;

	int                 err, i;

	const int sb_size = EM28XX_NUM_AUDIO_PACKETS *

			    EM28XX_AUDIO_MAX_PACKET_SIZE;

	int                 err, i, ep_size, interval, num_urb, npackets;

	int		    urb_size, bytes_per_transfer;

	u8 alt;



	if (!dev->has_alsa_audio || dev->audio_ifnum < 0) {
@@ -648,6 +663,9 @@ static int em28xx_audio_init(struct em28xx *dev) 
		return err;



	spin_lock_init(&adev->slock);

	adev->sndcard = card;

	adev->udev = dev->udev;



	err = snd_pcm_new(card, "Em28xx Audio", 0, 0, 1, &pcm);

	if (err < 0) {

		snd_card_free(card);
@@ -712,25 +730,92 @@ static int em28xx_audio_init(struct em28xx *dev) 
		return -ENODEV;

	}



	/* Alloc URB and transfer buffers */

	for (i = 0; i < EM28XX_AUDIO_BUFS; i++) {

	ep_size = em28xx_audio_ep_packet_size(dev->udev, ep);

	interval = 1 << (ep->bInterval - 1);



	em28xx_info("Endpoint 0x%02x %s on intf %d alt %d interval = %d, size %d\n",

		     EM28XX_EP_AUDIO, usb_speed_string(dev->udev->speed),

		     dev->audio_ifnum, alt,

		     interval,

		     ep_size);



	/* Calculate the number and size of URBs to better fit the audio samples */



	/*

	 * Estimate the number of bytes per DMA transfer.

	 *

	 * This is given by the bit rate (for now, only 48000 Hz) multiplied

	 * by 2 channels and 2 bytes/sample divided by the number of microframe

	 * intervals and by the microframe rate (125 us)

	 */

	bytes_per_transfer = DIV_ROUND_UP(48000 * 2 * 2, 125 * interval);



	/*

	 * Estimate the number of transfer URBs. Don't let it go past the

	 * maximum number of URBs that is known to be supported by the device.

	 */

	num_urb = DIV_ROUND_UP(bytes_per_transfer, ep_size);

	if (num_urb > EM28XX_MAX_AUDIO_BUFS)

		num_urb = EM28XX_MAX_AUDIO_BUFS;



	/*

	 * Now that we know the number of bytes per transfer and the number of

	 * URBs, estimate the typical size of an URB, in order to adjust the

	 * minimal number of packets.

	 */

	urb_size = bytes_per_transfer / num_urb;



	/*

	 * Now, calculate the amount of audio packets to be filled on each

	 * URB. In order to preserve the old behaviour, use a minimal

	 * threshold for this value.

	 */

	npackets = EM28XX_MIN_AUDIO_PACKETS;

	if (urb_size > ep_size * npackets)

		npackets = DIV_ROUND_UP(urb_size, ep_size);



	em28xx_info("Number of URBs: %d, with %d packets and %d size",

		    num_urb, npackets, urb_size);



	/* Allocate space to store the number of URBs to be used */



	dev->adev.transfer_buffer = kcalloc(num_urb,

					    sizeof(*dev->adev.transfer_buffer),

					    GFP_ATOMIC);

	if (!dev->adev.transfer_buffer) {

		snd_card_free(card);

		return -ENOMEM;

	}



	dev->adev.urb = kcalloc(num_urb, sizeof(*dev->adev.urb), GFP_ATOMIC);

	if (!dev->adev.urb) {

		snd_card_free(card);

		kfree(dev->adev.transfer_buffer);

		return -ENOMEM;

	}



	/* Alloc memory for each URB and for each transfer buffer */

	dev->adev.num_urb = num_urb;

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

		struct urb *urb;

		int j, k;

		void *buf;



		urb = usb_alloc_urb(EM28XX_NUM_AUDIO_PACKETS, GFP_ATOMIC);

		urb = usb_alloc_urb(npackets, GFP_ATOMIC);

		if (!urb) {

			em28xx_errdev("usb_alloc_urb failed!\n");

			em28xx_audio_free_urb(dev);

			snd_card_free(card);

			return -ENOMEM;

		}

		dev->adev.urb[i] = urb;



		buf = usb_alloc_coherent(dev->udev, sb_size, GFP_ATOMIC,

		buf = usb_alloc_coherent(dev->udev, npackets * ep_size, GFP_ATOMIC,

					 &urb->transfer_dma);

		if (!buf) {

			em28xx_errdev("usb_alloc_coherent failed!\n");

			em28xx_audio_free_urb(dev);

			snd_card_free(card);

			return -ENOMEM;

		}

		dev->adev.transfer_buffer[i] = buf;
@@ -739,23 +824,15 @@ static int em28xx_audio_init(struct em28xx *dev) 
		urb->context = dev;

		urb->pipe = usb_rcvisocpipe(dev->udev, EM28XX_EP_AUDIO);

		urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;

		urb->transfer_buffer = dev->adev.transfer_buffer[i];

		urb->interval = 1 << (ep->bInterval - 1);

		urb->transfer_buffer = buf;

		urb->interval = interval;

		urb->complete = em28xx_audio_isocirq;

		urb->number_of_packets = EM28XX_NUM_AUDIO_PACKETS;

		urb->transfer_buffer_length = sb_size;



		if (!i)

			dprintk("Will use ep 0x%02x on intf %d alt %d interval = %d (rcv isoc pipe: 0x%08x)\n",

				EM28XX_EP_AUDIO, dev->audio_ifnum, alt,

				urb->interval,

				urb->pipe);

		urb->number_of_packets = npackets;

		urb->transfer_buffer_length = ep_size * npackets;



		for (j = k = 0; j < EM28XX_NUM_AUDIO_PACKETS;

			     j++, k += EM28XX_AUDIO_MAX_PACKET_SIZE) {

		for (j = k = 0; j < npackets; j++, k += ep_size) {

			urb->iso_frame_desc[j].offset = k;

			urb->iso_frame_desc[j].length =

			    EM28XX_AUDIO_MAX_PACKET_SIZE;

			urb->iso_frame_desc[j].length = ep_size;

		}

	}
@@ -765,8 +842,6 @@ static int em28xx_audio_init(struct em28xx *dev) 
		snd_card_free(card);

		return err;

	}

	adev->sndcard = card;

	adev->udev = dev->udev;



	em28xx_info("Audio extension successfully initialized\n");

	return 0;

drivers/media/usb/em28xx/em28xx.h

+3 −5
Original line number Diff line number Diff line
@@ -481,9 +481,6 @@ struct em28xx_eeprom { 
	u8 string_idx_table;

};



#define EM28XX_AUDIO_BUFS 5

#define EM28XX_NUM_AUDIO_PACKETS 64

#define EM28XX_AUDIO_MAX_PACKET_SIZE 196 /* static value */

#define EM28XX_CAPTURE_STREAM_EN 1



/* em28xx extensions */
@@ -498,8 +495,9 @@ struct em28xx_eeprom { 


struct em28xx_audio {

	char name[50];

	char *transfer_buffer[EM28XX_AUDIO_BUFS];

	struct urb *urb[EM28XX_AUDIO_BUFS];

	unsigned num_urb;

	char **transfer_buffer;

	struct urb **urb;

	struct usb_device *udev;

	unsigned int capture_transfer_done;

	struct snd_pcm_substream   *capture_pcm_substream;