usb: musb: unmap dma buffer when switching to PIO

Buffer is mapped to dma when dma channel is
allocated. If, for some reason, dma channel
programming fails, musb code will fallback
to PIO mode to transfer that request. In
that case, we need to unmap the buffer
back to CPU.

MUSB RTL1.8 and above cannot handle buffers
which are not 32bit aligned. That happens to
every request sent by g_ether gadget
driver. Since the buffer sent was unaligned,
we need to fallback to PIO.

Because of that, g_ether was failing due
to missing buffer unmapping.

With this patch and [1] g_ether works fine
with all MUSB revisions.

Verified with OMAP3630 board, which has
MUSB RTL1.8 using g_ether and g_zero.

[1] http://www.spinics.net/lists/linux-usb/msg38400.html

Signed-off-by: Hema HK <hemahk@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_gadget.c

@@ -92,6 +92,59 @@
 
 /* ----------------------------------------------------------------------- */
 
+/* Maps the buffer to dma  */
+
+static inline void map_dma_buffer(struct musb_request *request,
+				struct musb *musb)
+{
+	if (request->request.dma == DMA_ADDR_INVALID) {
+		request->request.dma = dma_map_single(
+				musb->controller,
+				request->request.buf,
+				request->request.length,
+				request->tx
+					? DMA_TO_DEVICE
+					: DMA_FROM_DEVICE);
+		request->mapped = 1;
+	} else {
+		dma_sync_single_for_device(musb->controller,
+			request->request.dma,
+			request->request.length,
+			request->tx
+				? DMA_TO_DEVICE
+				: DMA_FROM_DEVICE);
+		request->mapped = 0;
+	}
+}
+
+/* Unmap the buffer from dma and maps it back to cpu */
+static inline void unmap_dma_buffer(struct musb_request *request,
+				struct musb *musb)
+{
+	if (request->request.dma == DMA_ADDR_INVALID) {
+		DBG(20, "not unmapping a never mapped buffer\n");
+		return;
+	}
+	if (request->mapped) {
+		dma_unmap_single(musb->controller,
+			request->request.dma,
+			request->request.length,
+			request->tx
+				? DMA_TO_DEVICE
+				: DMA_FROM_DEVICE);
+		request->request.dma = DMA_ADDR_INVALID;
+		request->mapped = 0;
+	} else {
+		dma_sync_single_for_cpu(musb->controller,
+			request->request.dma,
+			request->request.length,
+			request->tx
+				? DMA_TO_DEVICE
+				: DMA_FROM_DEVICE);
+
+	}
+}
+
 /*
  * Immediately complete a request.
  *
@@ -119,24 +172,8 @@ __acquires(ep->musb->lock)
 
 	ep->busy = 1;
 	spin_unlock(&musb->lock);
-	if (is_dma_capable()) {
-		if (req->mapped) {
-			dma_unmap_single(musb->controller,
-					req->request.dma,
-					req->request.length,
-					req->tx
-						? DMA_TO_DEVICE
-						: DMA_FROM_DEVICE);
-			req->request.dma = DMA_ADDR_INVALID;
-			req->mapped = 0;
-		} else if (req->request.dma != DMA_ADDR_INVALID)
-			dma_sync_single_for_cpu(musb->controller,
-					req->request.dma,
-					req->request.length,
-					req->tx
-						? DMA_TO_DEVICE
-						: DMA_FROM_DEVICE);
-	}
+	if (is_dma_capable() && ep->dma)
+		unmap_dma_buffer(req, musb);
 	if (request->status == 0)
 		DBG(5, "%s done request %p,  %d/%d\n",
 				ep->end_point.name, request,
@@ -395,6 +432,13 @@ static void txstate(struct musb *musb, struct musb_request *req)
 #endif
 
 	if (!use_dma) {
+		/*
+		 * Unmap the dma buffer back to cpu if dma channel
+		 * programming fails
+		 */
+		if (is_dma_capable() && musb_ep->dma)
+			unmap_dma_buffer(req, musb);
+
 		musb_write_fifo(musb_ep->hw_ep, fifo_count,
 				(u8 *) (request->buf + request->actual));
 		request->actual += fifo_count;
@@ -713,6 +757,20 @@ static void rxstate(struct musb *musb, struct musb_request *req)
 					return;
 			}
 #endif
+			/*
+			 * Unmap the dma buffer back to cpu if dma channel
+			 * programming fails. This buffer is mapped if the
+			 * channel allocation is successful
+			 */
+			 if (is_dma_capable() && musb_ep->dma) {
+				unmap_dma_buffer(req, musb);
+
+				/* Clear DMAENAB for the
+				 * PIO mode transfer
+				 */
+				csr &= ~MUSB_RXCSR_DMAENAB;
+				musb_writew(epio, MUSB_RXCSR, csr);
+			}
 
 			musb_read_fifo(musb_ep->hw_ep, fifo_count, (u8 *)
 					(request->buf + request->actual));
@@ -1150,26 +1208,9 @@ static int musb_gadget_queue(struct usb_ep *ep, struct usb_request *req,
 	request->epnum = musb_ep->current_epnum;
 	request->tx = musb_ep->is_in;
 
-	if (is_dma_capable() && musb_ep->dma) {
-		if (request->request.dma == DMA_ADDR_INVALID) {
-			request->request.dma = dma_map_single(
-					musb->controller,
-					request->request.buf,
-					request->request.length,
-					request->tx
-						? DMA_TO_DEVICE
-						: DMA_FROM_DEVICE);
-			request->mapped = 1;
-		} else {
-			dma_sync_single_for_device(musb->controller,
-					request->request.dma,
-					request->request.length,
-					request->tx
-						? DMA_TO_DEVICE
-						: DMA_FROM_DEVICE);
-			request->mapped = 0;
-		}
-	} else
+	if (is_dma_capable() && musb_ep->dma)
+		map_dma_buffer(request, musb);
+	else
 		request->mapped = 0;
 
 	spin_lock_irqsave(&musb->lock, lockflags);