usb: musb: gadget: fix ZLP sending in musb_g_tx(v1)

This patch fixes the problem reported by Sergei:

>how come? we need to send ZLP before giving back the request.
>Well, look at the code ionce again. We need to send ZLP *after*
>request->actual == request->length, but as the check is inserted
>after the ZLP send, ZLP *may* be sent once the first DMA completes,
>not the last.

The patch also has been discussed on the link below:

	http://marc.info/?t=128454814900001&r=1&w=2

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reported-by: Sergei Shtylyov <sshtylyov@mvista.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Anand Gadiyar <gadiyar@ti.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 29 insertions, 30 deletions

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 6a8c061b66f1..3f1cc5a8381f 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -477,40 +477,39 @@ void musb_g_tx(struct musb *musb, u8 epnum)
                                 epnum, csr, musb_ep->dma->actual_len, request);
                 }
 
-                if (is_dma || request->actual == request->length) {
-                        /*
-                         * First, maybe a terminating short packet. Some DMA
-                         * engines might handle this by themselves.
-                         */
-                        if ((request->zero && request->length
-                                && request->length % musb_ep->packet_sz == 0)
+                /*
+                 * First, maybe a terminating short packet. Some DMA
+                 * engines might handle this by themselves.
+                 */
+                if ((request->zero && request->length
+                        && (request->length % musb_ep->packet_sz == 0)
+                        && (request->actual == request->length))
 #ifdef CONFIG_USB_INVENTRA_DMA
-                                || (is_dma && (!dma->desired_mode ||
-                                        (request->actual &
-                                                (musb_ep->packet_sz - 1))))
+                        || (is_dma && (!dma->desired_mode ||
+                                (request->actual &
+                                        (musb_ep->packet_sz - 1))))
 #endif
-                        ) {
-                                /*
-                                 * On DMA completion, FIFO may not be
-                                 * available yet...
-                                 */
-                                if (csr & MUSB_TXCSR_TXPKTRDY)
-                                        return;
+                ) {
+                        /*
+                         * On DMA completion, FIFO may not be
+                         * available yet...
+                         */
+                        if (csr & MUSB_TXCSR_TXPKTRDY)
+                                return;
 
-                                DBG(4, "sending zero pkt\n");
-                                musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
-                                                | MUSB_TXCSR_TXPKTRDY);
-                                request->zero = 0;
-                        }
+                        DBG(4, "sending zero pkt\n");
+                        musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
+                                        | MUSB_TXCSR_TXPKTRDY);
+                        request->zero = 0;
+                }
 
-                        if (request->actual == request->length) {
-                                musb_g_giveback(musb_ep, request, 0);
-                                request = musb_ep->desc ? next_request(musb_ep) : NULL;
-                                if (!request) {
-                                        DBG(4, "%s idle now\n",
-                                                musb_ep->end_point.name);
-                                        return;
-                                }
+                if (request->actual == request->length) {
+                        musb_g_giveback(musb_ep, request, 0);
+                        request = musb_ep->desc ? next_request(musb_ep) : NULL;
+                        if (!request) {
+                                DBG(4, "%s idle now\n",
+                                        musb_ep->end_point.name);
+                                return;
                         }
                 }