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Subject[RESEND/PATCH 2/6] USB: musb-gadget: fix bulk IN infinite hangs in double buffer case
From: Ming Lei <>

This patch fixes one infinite hang of bulk IN transfer in double buffer
case, the hang can be observed easily by test #6 of usbtest if musb is
configured as g_zero and fifo mode 3 is taken to enable double fifo.

In fact, the patch only removes the check for non-empty fifo before
loading data from new request into fifo since the check is not correct:

-in double buffer case, fifo may accommodate more than one packet,
even though it has contained one packet already and is non-empty

-since last DMA is completed before calling musb_g_tx, it is sure
that fifo may accommodate at least one packet

Without applying the patch, new requst enqueued from .complte may not
have a chance to be loaded into fifo, then will never be completed and
cause infinite hangs.

With the patch, on my beagle B5, test#6(queued bulk in) can be passed and
test result may go beyond 33Mbyte/s if musb is configured as g_zero and
fifo mode 3 is taken, follows the test command:

#testusb -D DEV_NAME -c 1024 -t 6 -s 32768 -g 8 [1]

-source of testusb : tools/usb/testusb.c under linux kernel;

Signed-off-by: Ming Lei <>
Acked-by: Anand Gadiyar <>
Cc: David Brownell <>
Cc: Felipe Balbi <>
Cc: Anand Gadiyar <>
Cc: Mike Frysinger <>
Cc: Sergei Shtylyov <>
drivers/usb/musb/musb_gadget.c | 12 ------------
1 files changed, 0 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index de0ca90..f206c94 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -504,18 +504,6 @@ void musb_g_tx(struct musb *musb, u8 epnum)
/* ... or if not, then complete it. */
musb_g_giveback(musb_ep, request, 0);

- /*
- * Kickstart next transfer if appropriate;
- * the packet that just completed might not
- * be transmitted for hours or days.
- * REVISIT for double buffering...
- * FIXME revisit for stalls too...
- */
- musb_ep_select(mbase, epnum);
- csr = musb_readw(epio, MUSB_TXCSR);
- return;
request = musb_ep->desc ? next_request(musb_ep) : NULL;
if (!request) {
DBG(4, "%s idle now\n",

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