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    Subject[RESEND/PATCH 2/6] USB: musb-gadget: fix bulk IN infinite hangs in double buffer case
    Date
    From: Ming Lei <tom.leiming@gmail.com>

    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]

    [1],
    -source of testusb : tools/usb/testusb.c under linux kernel;

    Signed-off-by: Ming Lei <tom.leiming@gmail.com>
    Acked-by: Anand Gadiyar <gadiyar@ti.com>
    Cc: David Brownell <dbrownell@users.sourceforge.net>
    Cc: Felipe Balbi <me@felipebalbi.com>
    Cc: Anand Gadiyar <gadiyar@ti.com>
    Cc: Mike Frysinger <vapier@gentoo.org>
    Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
    ---
    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);
    - if (csr & MUSB_TXCSR_FIFONOTEMPTY)
    - return;
    -
    request = musb_ep->desc ? next_request(musb_ep) : NULL;
    if (!request) {
    DBG(4, "%s idle now\n",
    --
    1.6.2.5


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