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: Mauro Carvalho Chehab <m.chehab@xxxxxxxxxxx>
---
drivers/media/usb/em28xx/em28xx-audio.c | 141 ++++++++++++++++++++++++--------
drivers/media/usb/em28xx/em28xx.h | 8 +-
2 files changed, 111 insertions(+), 38 deletions(-)
diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c
index 4ee3488960e1..6c7d34600294 100644
--- a/drivers/media/usb/em28xx/em28xx-audio.c
+++ b/drivers/media/usb/em28xx/em28xx-audio.c
@@ -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;
- usb_free_coherent(dev->udev,
- urb->transfer_buffer_length,
- dev->adev.transfer_buffer[i],
- urb->transfer_dma);
+ 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;
diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
index efdf38642768..e76f993e3195 100644
--- a/drivers/media/usb/em28xx/em28xx.h
+++ b/drivers/media/usb/em28xx/em28xx.h
@@ -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;
--
1.8.3.1
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