[PATCH 1/2] MUSB: fix unhandled gadget endpoint 0 IRQs

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The driver incorrectly cancels the mass-storage device CSW request (which leads
to device reset) due to giving back URB at the head of endpoint's queue after
sending each STALL handshake; stop doing that and start checking for the queue
being non-empty before stalling an endpoint and disallowing stall in such case
in musb_gadget_set_halt() like the other gadget drivers do.

Moreover, the driver starts Rx request despite of the endpoint being halted --
fix this by moving the SendStall bit checking from musb_g_rx() to rxstate().
And we also sometimes get into rxstate() with DMA still active after clearing
an endpoint's halt (not clear why), so bail out in this case, similarly to what
txstate()'s does...

While at it, also do the following changes :

- in musb_gadget_set_halt(), remove pointless Tx FIFO flushing (the driver does
  not allow stalling with non-empty Tx FIFO anyway);

- in rxstate(), stop pointlessly zeroing the 'csr' variable;

- in musb_gadget_set_halt(), move the 'done' label to a more proper place

- in musb_g_rx(), eliminate the 'done' label completely...

---
This patch is atop of the Linus' tree plus 3 more patches posted earlier
that haven't made it into any tree yet:

http://marc.info/?l=linux-usb&m=123502258502676
http://marc.info/?l=linux-usb&m=123558766411239
http://marc.info/?l=linux-usb&m=123516211401715

It's a replacement (inexact -- it doesn't try to address issue with halting
gadget by host) for 3 patches posted by Swaminathan Subbramanian in December:

http://marc.info/?l=linux-usb&m=122831218103530
http://marc.info/?l=linux-usb&m=122838184202655
http://marc.info/?l=linux-usb&m=122840747806532

 drivers/usb/musb/musb_gadget.c |   79 +++++++++++++++++------------------------
 1 files changed, 34 insertions(+), 45 deletions(-)

Index: linux-2.6/drivers/usb/musb/musb_gadget.c
===================================================================
--- linux-2.6.orig/drivers/usb/musb/musb_gadget.c
+++ linux-2.6/drivers/usb/musb/musb_gadget.c
@@ -4,6 +4,7 @@
  * Copyright 2005 Mentor Graphics Corporation
  * Copyright (C) 2005-2006 by Texas Instruments
  * Copyright (C) 2006-2007 Nokia Corporation
+ * Copyright (C) 2009 MontaVista Software, Inc. <source@xxxxxxxxxx>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -435,14 +436,6 @@ void musb_g_tx(struct musb *musb, u8 epn
 			csr |= MUSB_TXCSR_P_WZC_BITS;
 			csr &= ~MUSB_TXCSR_P_SENTSTALL;
 			musb_writew(epio, MUSB_TXCSR, csr);
-			if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
-				dma->status = MUSB_DMA_STATUS_CORE_ABORT;
-				musb->dma_controller->channel_abort(dma);
-			}
-
-			if (request)
-				musb_g_giveback(musb_ep, request, -EPIPE);
-
 			break;
 		}
 
@@ -581,15 +574,25 @@ void musb_g_tx(struct musb *musb, u8 epn
  */
 static void rxstate(struct musb *musb, struct musb_request *req)
 {
-	u16			csr = 0;
 	const u8		epnum = req->epnum;
 	struct usb_request	*request = &req->request;
 	struct musb_ep		*musb_ep = &musb->endpoints[epnum].ep_out;
 	void __iomem		*epio = musb->endpoints[epnum].regs;
 	unsigned		fifo_count = 0;
 	u16			len = musb_ep->packet_sz;
+	u16			csr = musb_readw(epio, MUSB_RXCSR);
 
-	csr = musb_readw(epio, MUSB_RXCSR);
+	/* We shouldn't get here while DMA is active, but we do... */
+	if (dma_channel_status(musb_ep->dma) == MUSB_DMA_STATUS_BUSY) {
+		DBG(4, "DMA pending...\n");
+		return;
+	}
+
+	if (csr & MUSB_RXCSR_P_SENDSTALL) {
+		DBG(5, "%s stalling, RXCSR %04x\n",
+		    musb_ep->end_point.name, csr);
+		return;
+	}
 
 	if (is_cppi_enabled() && musb_ep->dma) {
 		struct dma_controller	*c = musb->dma_controller;
@@ -760,19 +763,10 @@ void musb_g_rx(struct musb *musb, u8 epn
 			csr, dma ? " (dma)" : "", request);
 
 	if (csr & MUSB_RXCSR_P_SENTSTALL) {
-		if (dma_channel_status(dma) == MUSB_DMA_STATUS_BUSY) {
-			dma->status = MUSB_DMA_STATUS_CORE_ABORT;
-			(void) musb->dma_controller->channel_abort(dma);
-			request->actual += musb_ep->dma->actual_len;
-		}
-
 		csr |= MUSB_RXCSR_P_WZC_BITS;
 		csr &= ~MUSB_RXCSR_P_SENTSTALL;
 		musb_writew(epio, MUSB_RXCSR, csr);
-
-		if (request)
-			musb_g_giveback(musb_ep, request, -EPIPE);
-		goto done;
+		return;
 	}
 
 	if (csr & MUSB_RXCSR_P_OVERRUN) {
@@ -794,7 +788,7 @@ void musb_g_rx(struct musb *musb, u8 epn
 		DBG((csr & MUSB_RXCSR_DMAENAB) ? 4 : 1,
 			"%s busy, csr %04x\n",
 			musb_ep->end_point.name, csr);
-		goto done;
+		return;
 	}
 
 	if (dma && (csr & MUSB_RXCSR_DMAENAB)) {
@@ -825,22 +819,15 @@ void musb_g_rx(struct musb *musb, u8 epn
 		if ((request->actual < request->length)
 				&& (musb_ep->dma->actual_len
 					== musb_ep->packet_sz))
-			goto done;
+			return;
 #endif
 		musb_g_giveback(musb_ep, request, 0);
 
 		request = next_request(musb_ep);
 		if (!request)
-			goto done;
-
-		/* don't start more i/o till the stall clears */
-		musb_ep_select(mbase, epnum);
-		csr = musb_readw(epio, MUSB_RXCSR);
-		if (csr & MUSB_RXCSR_P_SENDSTALL)
-			goto done;
+			return;
 	}
 
-
 	/* analyze request if the ep is hot */
 	if (request)
 		rxstate(musb, to_musb_request(request));
@@ -848,8 +835,6 @@ void musb_g_rx(struct musb *musb, u8 epn
 		DBG(3, "packet waiting for %s%s request\n",
 				musb_ep->desc ? "" : "inactive ",
 				musb_ep->end_point.name);
-
-done:
 	return;
 }
 
@@ -1243,7 +1228,7 @@ int musb_gadget_set_halt(struct usb_ep *
 	void __iomem		*mbase;
 	unsigned long		flags;
 	u16			csr;
-	struct musb_request	*request = NULL;
+	struct musb_request	*request;
 	int			status = 0;
 
 	if (!ep)
@@ -1259,24 +1244,29 @@ int musb_gadget_set_halt(struct usb_ep *
 
 	musb_ep_select(mbase, epnum);
 
-	/* cannot portably stall with non-empty FIFO */
 	request = to_musb_request(next_request(musb_ep));
-	if (value && musb_ep->is_in) {
-		csr = musb_readw(epio, MUSB_TXCSR);
-		if (csr & MUSB_TXCSR_FIFONOTEMPTY) {
-			DBG(3, "%s fifo busy, cannot halt\n", ep->name);
-			spin_unlock_irqrestore(&musb->lock, flags);
-			return -EAGAIN;
+	if (value) {
+		if (request) {
+			DBG(3, "request in progress, cannot halt %s\n",
+			    ep->name);
+			status = -EAGAIN;
+			goto done;
+		}
+		/* Cannot portably stall with non-empty FIFO */
+		if (musb_ep->is_in) {
+			csr = musb_readw(epio, MUSB_TXCSR);
+			if (csr & MUSB_TXCSR_FIFONOTEMPTY) {
+				DBG(3, "FIFO busy, cannot halt %s\n", ep->name);
+				status = -EAGAIN;
+				goto done;
+			}
 		}
-
 	}
 
 	/* set/clear the stall and toggle bits */
 	DBG(2, "%s: %s stall\n", ep->name, value ? "set" : "clear");
 	if (musb_ep->is_in) {
 		csr = musb_readw(epio, MUSB_TXCSR);
-		if (csr & MUSB_TXCSR_FIFONOTEMPTY)
-			csr |= MUSB_TXCSR_FLUSHFIFO;
 		csr |= MUSB_TXCSR_P_WZC_BITS
 			| MUSB_TXCSR_CLRDATATOG;
 		if (value)
@@ -1299,14 +1289,13 @@ int musb_gadget_set_halt(struct usb_ep *
 		musb_writew(epio, MUSB_RXCSR, csr);
 	}
 
-done:
-
 	/* maybe start the first request in the queue */
 	if (!musb_ep->busy && !value && request) {
 		DBG(3, "restarting the request\n");
 		musb_ep_restart(musb, request);
 	}
 
+done:
 	spin_unlock_irqrestore(&musb->lock, flags);
 	return status;
 }

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