Workaround for receiving Voice Calls using the E1750 dongle from

Huawei. It might appear as if the firmware is allocating memory blocks
according to the USB transfer size and if there is initially a lot of
data, like at the answering machine prompt, it simply dies without any
apparent reason. The simple workaround for this is to force a zero
length packet at hardware level after every 512 bytes of data. This
will force the other side to use smaller memory blocks aswell.

MFC after:	1 week

1 files changed, 14 insertions, 3 deletions

diff --git a/sys/dev/usb/serial/u3g.c b/sys/dev/usb/serial/u3g.c
index bbf5351..59215e4 100644
--- a/sys/dev/usb/serial/u3g.c
+++ b/sys/dev/usb/serial/u3g.c
@@ -75,6 +75,8 @@ SYSCTL_INT(_hw_usb_u3g, OID_AUTO, debug, CTLFLAG_RW,
 #define	U3G_MAXPORTS		12
 #define	U3G_CONFIG_INDEX	0
 #define	U3G_BSIZE		2048
+#define	U3G_TXSIZE		(U3G_BSIZE / U3G_TXFRAMES)
+#define	U3G_TXFRAMES		4
 
 /* Eject methods; See also usb_quirks.h:UQ_MSC_EJECT_* */
 #define	U3GINIT_HUAWEI		1	/* Requires Huawei init command */
@@ -145,6 +147,7 @@ static const struct usb_config u3g_config[U3G_N_TRANSFER] = {
 		.endpoint = UE_ADDR_ANY,
 		.direction = UE_DIR_OUT,
 		.bufsize = U3G_BSIZE,/* bytes */
+		.frames = U3G_TXFRAMES,
 		.flags = {.pipe_bof = 1,.force_short_xfer = 1,},
 		.callback = &u3g_write_callback,
 	},
@@ -1011,14 +1014,22 @@ u3g_write_callback(struct usb_xfer *xfer, usb_error_t error)
 	struct ucom_softc *ucom = usbd_xfer_softc(xfer);
 	struct usb_page_cache *pc;
 	uint32_t actlen;
+	uint32_t frame;
 
 	switch (USB_GET_STATE(xfer)) {
 	case USB_ST_TRANSFERRED:
 	case USB_ST_SETUP:
 tr_setup:
-		pc = usbd_xfer_get_frame(xfer, 0);
-		if (ucom_get_data(ucom, pc, 0, U3G_BSIZE, &actlen)) {
-			usbd_xfer_set_frame_len(xfer, 0, actlen);
+		for (frame = 0; frame != U3G_TXFRAMES; frame++) {
+			usbd_xfer_set_frame_offset(xfer, frame * U3G_TXSIZE, frame);
+
+			pc = usbd_xfer_get_frame(xfer, frame);
+			if (ucom_get_data(ucom, pc, 0, U3G_TXSIZE, &actlen) == 0)
+				break;
+			usbd_xfer_set_frame_len(xfer, frame, actlen);
+		}
+		if (frame != 0) {
+			usbd_xfer_set_frames(xfer, frame);
 			usbd_transfer_submit(xfer);
 		}
 		break;