[Qemu-devel] [PATCH 03/14] usb-linux: Add support for buffering iso usb packets

[Gerd Hoffmann]

From: Hans de Goede <address@hidden>

Currently we are submitting iso packets to the host one at a time, as we
receive them from the emulated host controller. This has 2 problems:
1) If we were fast enough to submit every packet in time for the next host host
controller usb frame, we would be generating 1000 hardware interrupts per
second on the host
2) We are not fast enough to submit every packet in time for the next host host
controller usb frame, causing us to not submit iso urbs in some usb frames
which causes devices with an endpoint with an interval of 1 ms (so every
frame) to loose data. This causes for example ubs-1.1 webcams to not work
properly (usb-2.0 is not supported at all atm).

This patch fixes both problems by changing the iso packet pass through handling
to buffer packets. This version only does so for iso input packets (webcams,
audio in) I'm working on a second patch extending this to iso output packets
(audio out).

This patch makes use of the linux batching of iso packets in one urb.
When an iso in packet gets received from the emulated host controller,
it immediately submits 3 urbs with 32 iso in packets each. This causes
the host to only get an hw interrupt every 32 packets dropping the
interrupt rate to 32 interrupts per second and gives it a queue of urbs
to work from once the first 32 iso in packets have been received to make sure
no packets are dropped.

Besides submitting a whole bunch or urbs as soon as the first urb is
received, effectively creating a buffer inside the kernel, this patch also
gets rid of the asynchroneous completion for iso in urbs. Instead they are
only marked as complete in the fd write callback (which usbfs uses to signal
complete urbs). These complete packets then get consumed by returning them
synchroneously to the emulated host controller when it submits an iso in
packet for the ep in question. When no complete packets are ready (which
happens when the stream is starting) a 0 length packet gets returned to
the emulated host controller.

With this patch I've several usb-1.1 webcams working well with usb pass
through, where as without this patch none of them work.

Signed-off-by: Hans de Goede <address@hidden>
Signed-off-by: Gerd Hoffmann <address@hidden>
---
 usb-linux.c |  243 ++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 226 insertions(+), 17 deletions(-)

diff --git a/usb-linux.c b/usb-linux.c
index f4601e6..a68603d 100644
--- a/usb-linux.c
+++ b/usb-linux.c
@@ -92,9 +92,17 @@ static char *usb_host_device_path;
 static int usb_fs_type;
 
 /* endpoint association data */
+#define ISO_FRAME_DESC_PER_URB 32
+#define ISO_URB_COUNT 3
+
+typedef struct AsyncURB AsyncURB;
+
 struct endp_data {
     uint8_t type;
     uint8_t halted;
+    AsyncURB *iso_urb;
+    int iso_urb_idx;
+    int max_packet_size;
 };
 
 enum {
@@ -175,19 +183,48 @@ static void set_halt(USBHostDevice *s, int ep)
     s->endp_table[ep - 1].halted = 1;
 }
 
+static void set_iso_urb(USBHostDevice *s, int ep, AsyncURB *iso_urb)
+{
+    s->endp_table[ep - 1].iso_urb = iso_urb;
+}
+
+static AsyncURB *get_iso_urb(USBHostDevice *s, int ep)
+{
+    return s->endp_table[ep - 1].iso_urb;
+}
+
+static void set_iso_urb_idx(USBHostDevice *s, int ep, int i)
+{
+    s->endp_table[ep - 1].iso_urb_idx = i;
+}
+
+static int get_iso_urb_idx(USBHostDevice *s, int ep)
+{
+    return s->endp_table[ep - 1].iso_urb_idx;
+}
+
+static int get_max_packet_size(USBHostDevice *s, int ep)
+{
+    return s->endp_table[ep - 1].max_packet_size;
+}
+
 /*
  * Async URB state.
- * We always allocate one isoc descriptor even for bulk transfers
+ * We always allocate iso packet descriptors even for bulk transfers
  * to simplify allocation and casts.
  */
-typedef struct AsyncURB
+struct AsyncURB
 {
     struct usbdevfs_urb urb;
-    struct usbdevfs_iso_packet_desc isocpd;
+    struct usbdevfs_iso_packet_desc isocpd[ISO_FRAME_DESC_PER_URB];
 
+    /* For regular async urbs */
     USBPacket     *packet;
     USBHostDevice *hdev;
-} AsyncURB;
+
+    /* For buffered iso handling */
+    int iso_frame_idx; /* -1 means in flight */
+};
 
 static AsyncURB *async_alloc(void)
 {
@@ -244,11 +281,21 @@ static void async_complete(void *opaque)
             return;
         }
 
-        p = aurb->packet;
-
         DPRINTF("husb: async completed. aurb %p status %d alen %d\n",
                 aurb, aurb->urb.status, aurb->urb.actual_length);
 
+        /* If this is a buffered iso urb mark it as complete and don't do
+           anything else (it is handled further in usb_host_handle_iso_data) */
+        if (aurb->iso_frame_idx == -1) {
+            if (aurb->urb.status == -EPIPE) {
+                set_halt(s, aurb->urb.endpoint & 0xf);
+            }
+            aurb->iso_frame_idx = 0;
+            continue;
+        }
+
+        p = aurb->packet;
+
         if (p) {
             switch (aurb->urb.status) {
             case 0:
@@ -415,34 +462,181 @@ static void usb_host_handle_destroy(USBDevice *dev)
 
 static int usb_linux_update_endp_table(USBHostDevice *s);
 
+/* iso data is special, we need to keep enough urbs in flight to make sure
+   that the controller never runs out of them, otherwise the device will
+   likely suffer a buffer underrun / overrun. */
+static AsyncURB *usb_host_alloc_iso(USBHostDevice *s, uint8_t ep, int in)
+{
+    AsyncURB *aurb;
+    int i, j, len = get_max_packet_size(s, ep);
+
+    aurb = qemu_mallocz(ISO_URB_COUNT * sizeof(*aurb));
+    for (i = 0; i < ISO_URB_COUNT; i++) {
+        aurb[i].urb.endpoint      = ep;
+        aurb[i].urb.buffer_length = ISO_FRAME_DESC_PER_URB * len;
+        aurb[i].urb.buffer        = qemu_malloc(aurb[i].urb.buffer_length);
+        aurb[i].urb.type          = USBDEVFS_URB_TYPE_ISO;
+        aurb[i].urb.flags         = USBDEVFS_URB_ISO_ASAP;
+        aurb[i].urb.number_of_packets = ISO_FRAME_DESC_PER_URB;
+        for (j = 0 ; j < ISO_FRAME_DESC_PER_URB; j++)
+            aurb[i].urb.iso_frame_desc[j].length = len;
+        if (in) {
+            aurb[i].urb.endpoint |= 0x80;
+            /* Mark as fully consumed (idle) */
+            aurb[i].iso_frame_idx = ISO_FRAME_DESC_PER_URB;
+        }
+    }
+    set_iso_urb(s, ep, aurb);
+
+    return aurb;
+}
+
+static void usb_host_stop_n_free_iso(USBHostDevice *s, uint8_t ep)
+{
+    AsyncURB *aurb;
+    int i, ret, killed = 0, free = 1;
+
+    aurb = get_iso_urb(s, ep);
+    if (!aurb) {
+        return;
+    }
+
+    for (i = 0; i < ISO_URB_COUNT; i++) {
+        /* in flight? */
+        if (aurb[i].iso_frame_idx == -1) {
+            ret = ioctl(s->fd, USBDEVFS_DISCARDURB, &aurb[i]);
+            if (ret < 0) {
+                printf("husb: discard isoc in urb failed errno %d\n", errno);
+                free = 0;
+                continue;
+            }
+            killed++;
+        }
+    }
+
+    /* Make sure any urbs we've killed are reaped before we free them */
+    if (killed) {
+        async_complete(s);
+    }
+
+    for (i = 0; i < ISO_URB_COUNT; i++) {
+        qemu_free(aurb[i].urb.buffer);
+    }
+
+    if (free)
+        qemu_free(aurb);
+    else
+        printf("husb: leaking iso urbs because of discard failure\n");
+    set_iso_urb(s, ep, NULL);
+}
+
+static int urb_status_to_usb_ret(int status)
+{
+    switch (status) {
+    case -EPIPE:
+        return USB_RET_STALL;
+    default:
+        return USB_RET_NAK;
+    }
+}
+
+static int usb_host_handle_iso_data(USBHostDevice *s, USBPacket *p)
+{
+    AsyncURB *aurb;
+    int i, j, ret, len = 0;
+
+    aurb = get_iso_urb(s, p->devep);
+    if (!aurb) {
+        aurb = usb_host_alloc_iso(s, p->devep, 1);
+    }
+
+    i = get_iso_urb_idx(s, p->devep);
+    j = aurb[i].iso_frame_idx;
+    if (j >= 0 && j < ISO_FRAME_DESC_PER_URB) {
+        /* Check urb status  */
+        if (aurb[i].urb.status) {
+            len = urb_status_to_usb_ret(aurb[i].urb.status);
+            /* Move to the next urb */
+            aurb[i].iso_frame_idx = ISO_FRAME_DESC_PER_URB - 1;
+        /* Check frame status */
+        } else if (aurb[i].urb.iso_frame_desc[j].status) {
+            len = urb_status_to_usb_ret(aurb[i].urb.iso_frame_desc[j].status);
+        /* Check the frame fits */
+        } else if (aurb[i].urb.iso_frame_desc[j].actual_length > p->len) {
+            printf("husb: error received isoc data is larger then packet\n");
+            len = USB_RET_NAK;
+        /* All good copy data over */
+        } else {
+            len = aurb[i].urb.iso_frame_desc[j].actual_length;
+            memcpy(p->data,
+                   aurb[i].urb.buffer +
+                       j * aurb[i].urb.iso_frame_desc[0].length,
+                   len);
+        }
+        aurb[i].iso_frame_idx++;
+        if (aurb[i].iso_frame_idx == ISO_FRAME_DESC_PER_URB) {
+            i = (i + 1) % ISO_URB_COUNT;
+            set_iso_urb_idx(s, p->devep, i);
+        }
+    }
+
+    /* (Re)-submit all fully consumed urbs */
+    for (i = 0; i < ISO_URB_COUNT; i++) {
+        if (aurb[i].iso_frame_idx == ISO_FRAME_DESC_PER_URB) {
+            ret = ioctl(s->fd, USBDEVFS_SUBMITURB, &aurb[i]);
+            if (ret < 0) {
+                printf("husb error submitting isoc urb %d: %d\n", i, errno);
+                if (len == 0) {
+                    switch(errno) {
+                    case ETIMEDOUT:
+                        len = USB_RET_NAK;
+                    case EPIPE:
+                    default:
+                        len = USB_RET_STALL;
+                    }
+                }
+                break;
+            }
+            aurb[i].iso_frame_idx = -1;
+        }
+    }
+
+    return len;
+}
+
 static int usb_host_handle_data(USBHostDevice *s, USBPacket *p)
 {
     struct usbdevfs_urb *urb;
     AsyncURB *aurb;
     int ret;
-
-    aurb = async_alloc();
-    aurb->hdev   = s;
-    aurb->packet = p;
-
-    urb = &aurb->urb;
+    uint8_t ep;
 
     if (p->pid == USB_TOKEN_IN) {
-        urb->endpoint = p->devep | 0x80;
+        ep = p->devep | 0x80;
     } else {
-        urb->endpoint = p->devep;
+        ep = p->devep;
     }
 
     if (is_halted(s, p->devep)) {
-        ret = ioctl(s->fd, USBDEVFS_CLEAR_HALT, &urb->endpoint);
+        ret = ioctl(s->fd, USBDEVFS_CLEAR_HALT, &ep);
         if (ret < 0) {
             DPRINTF("husb: failed to clear halt. ep 0x%x errno %d\n",
-                   urb->endpoint, errno);
+                   ep, errno);
             return USB_RET_NAK;
         }
         clear_halt(s, p->devep);
     }
 
+    if (is_isoc(s, p->devep) && p->pid == USB_TOKEN_IN)
+        return usb_host_handle_iso_data(s, p);
+
+    aurb = async_alloc();
+    aurb->hdev   = s;
+    aurb->packet = p;
+
+    urb = &aurb->urb;
+
+    urb->endpoint      = ep;
     urb->buffer        = p->data;
     urb->buffer_length = p->len;
 
@@ -515,7 +709,13 @@ static int usb_host_set_config(USBHostDevice *s, int 
config)
 static int usb_host_set_interface(USBHostDevice *s, int iface, int alt)
 {
     struct usbdevfs_setinterface si;
-    int ret;
+    int i, ret;
+
+    for (i = 1; i < MAX_ENDPOINTS; i++) {
+        if (is_isoc(s, i)) {
+            usb_host_stop_n_free_iso(s, i);
+        }
+    }
 
     si.interface  = iface;
     si.altsetting = alt;
@@ -927,6 +1127,8 @@ static int usb_linux_update_endp_table(USBHostDevice *s)
                 break;
             case 0x01:
                 type = USBDEVFS_URB_TYPE_ISO;
+                s->endp_table[(devep & 0xf) - 1].max_packet_size =
+                    descriptors[i + 4] + (descriptors[i + 5] << 8);
                 break;
             case 0x02:
                 type = USBDEVFS_URB_TYPE_BULK;
@@ -1049,12 +1251,19 @@ fail:
 
 static int usb_host_close(USBHostDevice *dev)
 {
+    int i;
+
     if (dev->fd == -1) {
         return -1;
     }
 
     qemu_set_fd_handler(dev->fd, NULL, NULL, NULL);
     dev->closing = 1;
+    for (i = 1; i < MAX_ENDPOINTS; i++) {
+        if (is_isoc(dev, i)) {
+            usb_host_stop_n_free_iso(dev, i);
+        }
+    }
     async_complete(dev);
     dev->closing = 0;
     usb_device_detach(&dev->dev);
-- 
1.7.1