usb: gadget: musb: fix short isoc packets with inventra dma

commit c418fd6c01fbc5516a2cd1eaf1df1ec86869028a upstream.

Handling short packets (length < max packet size) in the Inventra DMA
engine in the MUSB driver causes the MUSB DMA controller to hang. An
example of a problem that is caused by this problem is when streaming
video out of a UVC gadget, only the first video frame is transferred.

For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
set manually by the driver. This was previously done in musb_g_tx
(musb_gadget.c), but incorrectly (all csr flags were cleared, and only
MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY were set). Fixing that problem
allows some requests to be transferred correctly, but multiple requests
were often put together in one USB packet, and caused problems if the
packet size was not a multiple of 4. Instead, set MUSB_TXCSR_TXPKTRDY
in dma_controller_irq (musbhsdma.c), just like host mode transfers.

This topic was originally tackled by Nicolas Boichat [0] [1] and is
discussed further at [2] as part of his GSoC project [3].

[0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
[1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
[2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
[3] http://elinux.org/BeagleBoard/GSoC/USBSniffer

Fixes: 550a7375fe72 ("USB: Add MUSB and TUSB support")
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16:
 - Fold in the earlier commit fb91cddc54e7 "usb: musb: Remove DMA ifdef
   for musb_gadget.c short_packet"
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

2 files changed, 14 insertions, 20 deletions

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index d4aa779339f1..4258766799e1 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -488,10 +488,8 @@ void musb_g_tx(struct musb *musb, u8 epnum)
 	}
 
 	if (request) {
-		u8	is_dma = 0;
 
 		if (dma && (csr & MUSB_TXCSR_DMAENAB)) {
-			is_dma = 1;
 			csr |= MUSB_TXCSR_P_WZC_BITS;
 			csr &= ~(MUSB_TXCSR_DMAENAB | MUSB_TXCSR_P_UNDERRUN |
 				 MUSB_TXCSR_TXPKTRDY | MUSB_TXCSR_AUTOSET);
@@ -507,15 +505,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
 		 * First, maybe a terminating short packet. Some DMA
 		 * engines might handle this by themselves.
 		 */
-		if ((request->zero && request->length
+		if ((request->zero && request->length)
 			&& (request->length % musb_ep->packet_sz == 0)
-			&& (request->actual == request->length))
-#if defined(CONFIG_USB_INVENTRA_DMA) || defined(CONFIG_USB_UX500_DMA)
-			|| (is_dma && (!dma->desired_mode ||
-				(request->actual &
-					(musb_ep->packet_sz - 1))))
-#endif
-		) {
+			&& (request->actual == request->length)) {
+
 			/*
 			 * On DMA completion, FIFO may not be
 			 * available yet...
diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
index e8e9f9aab203..d006f54d5e15 100644
--- a/drivers/usb/musb/musbhsdma.c
+++ b/drivers/usb/musb/musbhsdma.c
@@ -319,12 +319,10 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
 				channel->status = MUSB_DMA_STATUS_FREE;
 
 				/* completed */
-				if ((devctl & MUSB_DEVCTL_HM)
-					&& (musb_channel->transmit)
-					&& ((channel->desired_mode == 0)
-					    || (channel->actual_len &
-					    (musb_channel->max_packet_sz - 1)))
-				    ) {
+				if (musb_channel->transmit &&
+					(!channel->desired_mode ||
+					(channel->actual_len %
+					    musb_channel->max_packet_sz))) {
 					u8  epnum  = musb_channel->epnum;
 					int offset = MUSB_EP_OFFSET(epnum,
 								    MUSB_TXCSR);
@@ -336,11 +334,14 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
 					 */
 					musb_ep_select(mbase, epnum);
 					txcsr = musb_readw(mbase, offset);
-					txcsr &= ~(MUSB_TXCSR_DMAENAB
+					if (channel->desired_mode == 1) {
+						txcsr &= ~(MUSB_TXCSR_DMAENAB
 							| MUSB_TXCSR_AUTOSET);
-					musb_writew(mbase, offset, txcsr);
-					/* Send out the packet */
-					txcsr &= ~MUSB_TXCSR_DMAMODE;
+						musb_writew(mbase, offset, txcsr);
+						/* Send out the packet */
+						txcsr &= ~MUSB_TXCSR_DMAMODE;
+						txcsr |= MUSB_TXCSR_DMAENAB;
+					}
 					txcsr |=  MUSB_TXCSR_TXPKTRDY;
 					musb_writew(mbase, offset, txcsr);
 				}