musb_gadget: fix unhandled endpoint 0 IRQs

The gadget EP0 code routinely ignores an interrupt at end of
the data phase because of musb_g_ep0_giveback() resetting the
state machine to "idle, waiting for SETUP" phase prematurely.

The driver also prematurely leaves the status phase on
receiving the SetupEnd interrupt.

As there were still unhandled endpoint 0 interrupts happening
from time to time after fixing these issues, there turned to
be yet another culprit: two distinct gadget states collapsed
into one.

The (missing) state that comes after STATUS IN/OUT states was
typically indiscernible from them since the corresponding
interrupts tend to happen within too little period of time
(due to only a zero-length status packet in between) and so
they got coalesced; yet this state is not the same as the next
one which is associated with the reception of a SETUP packet.

Adding this extra state seems to have fixed the rest of the
unhandled interrupts that generic_interrupt() and
davinci_interrupt() hid by faking their result and only
emitting a debug message -- so, stop doing that.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/musb/davinci.c

@@ -372,12 +372,7 @@ static irqreturn_t davinci_interrupt(int irq, void *__hci)
 
 	spin_unlock_irqrestore(&musb->lock, flags);
 
-	/* REVISIT we sometimes get unhandled IRQs
-	 * (e.g. ep0).  not clear why...
-	 */
-	if (retval != IRQ_HANDLED)
-		DBG(5, "unhandled? %08x\n", tmp);
-	return IRQ_HANDLED;
+	return retval;
 }
 
 int musb_platform_set_mode(struct musb *musb, u8 mode)

drivers/usb/musb/musb_core.c

@@ -1481,13 +1481,7 @@ static irqreturn_t generic_interrupt(int irq, void *__hci)
 
 	spin_unlock_irqrestore(&musb->lock, flags);
 
-	/* REVISIT we sometimes get spurious IRQs on g_ep0
-	 * not clear why...
-	 */
-	if (retval != IRQ_HANDLED)
-		DBG(5, "spurious?\n");
-
-	return IRQ_HANDLED;
+	return retval;
 }
 
 #else

drivers/usb/musb/musb_core.h

@@ -171,7 +171,8 @@ enum musb_h_ep0_state {
 
 /* peripheral side ep0 states */
 enum musb_g_ep0_state {
-	MUSB_EP0_STAGE_SETUP,		/* idle, waiting for setup */
+	MUSB_EP0_STAGE_IDLE,		/* idle, waiting for SETUP */
+	MUSB_EP0_STAGE_SETUP,		/* received SETUP */
 	MUSB_EP0_STAGE_TX,		/* IN data */
 	MUSB_EP0_STAGE_RX,		/* OUT data */
 	MUSB_EP0_STAGE_STATUSIN,	/* (after OUT data) */

drivers/usb/musb/musb_gadget_ep0.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) 2008-2009 MontaVista Software, Inc. <source@mvista.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -58,7 +59,8 @@
 static char *decode_ep0stage(u8 stage)
 {
 	switch (stage) {
-	case MUSB_EP0_STAGE_SETUP:	return "idle";
+	case MUSB_EP0_STAGE_IDLE:	return "idle";
+	case MUSB_EP0_STAGE_SETUP:	return "setup";
 	case MUSB_EP0_STAGE_TX:		return "in";
 	case MUSB_EP0_STAGE_RX:		return "out";
 	case MUSB_EP0_STAGE_ACKWAIT:	return "wait";
@@ -628,15 +630,26 @@ irqreturn_t musb_g_ep0_irq(struct musb *musb)
 		musb_writew(regs, MUSB_CSR0,
 				csr & ~MUSB_CSR0_P_SENTSTALL);
 		retval = IRQ_HANDLED;
-		musb->ep0_state = MUSB_EP0_STAGE_SETUP;
+		musb->ep0_state = MUSB_EP0_STAGE_IDLE;
 		csr = musb_readw(regs, MUSB_CSR0);
 	}
 
 	/* request ended "early" */
 	if (csr & MUSB_CSR0_P_SETUPEND) {
 		musb_writew(regs, MUSB_CSR0, MUSB_CSR0_P_SVDSETUPEND);
 		retval = IRQ_HANDLED;
-		musb->ep0_state = MUSB_EP0_STAGE_SETUP;
+		/* Transition into the early status phase */
+		switch (musb->ep0_state) {
+		case MUSB_EP0_STAGE_TX:
+			musb->ep0_state = MUSB_EP0_STAGE_STATUSOUT;
+			break;
+		case MUSB_EP0_STAGE_RX:
+			musb->ep0_state = MUSB_EP0_STAGE_STATUSIN;
+			break;
+		default:
+			ERR("SetupEnd came in a wrong ep0stage %s",
+			    decode_ep0stage(musb->ep0_state));
+		}
 		csr = musb_readw(regs, MUSB_CSR0);
 		/* NOTE:  request may need completion */
 	}
@@ -697,11 +710,31 @@ irqreturn_t musb_g_ep0_irq(struct musb *musb)
 			if (req)
 				musb_g_ep0_giveback(musb, req);
 		}
+
+		/*
+		 * In case when several interrupts can get coalesced,
+		 * check to see if we've already received a SETUP packet...
+		 */
+		if (csr & MUSB_CSR0_RXPKTRDY)
+			goto setup;
+
+		retval = IRQ_HANDLED;
+		musb->ep0_state = MUSB_EP0_STAGE_IDLE;
+		break;
+
+	case MUSB_EP0_STAGE_IDLE:
+		/*
+		 * This state is typically (but not always) indiscernible
+		 * from the status states since the corresponding interrupts
+		 * tend to happen within too little period of time (with only
+		 * a zero-length packet in between) and so get coalesced...
+		 */
 		retval = IRQ_HANDLED;
 		musb->ep0_state = MUSB_EP0_STAGE_SETUP;
 		/* FALLTHROUGH */
 
 	case MUSB_EP0_STAGE_SETUP:
+setup:
 		if (csr & MUSB_CSR0_RXPKTRDY) {
 			struct usb_ctrlrequest	setup;
 			int			handled = 0;
@@ -783,7 +816,7 @@ irqreturn_t musb_g_ep0_irq(struct musb *musb)
 stall:
 				DBG(3, "stall (%d)\n", handled);
 				musb->ackpend |= MUSB_CSR0_P_SENDSTALL;
-				musb->ep0_state = MUSB_EP0_STAGE_SETUP;
+				musb->ep0_state = MUSB_EP0_STAGE_IDLE;
 finish:
 				musb_writew(regs, MUSB_CSR0,
 						musb->ackpend);
@@ -803,7 +836,7 @@ irqreturn_t musb_g_ep0_irq(struct musb *musb)
 		/* "can't happen" */
 		WARN_ON(1);
 		musb_writew(regs, MUSB_CSR0, MUSB_CSR0_P_SENDSTALL);
-		musb->ep0_state = MUSB_EP0_STAGE_SETUP;
+		musb->ep0_state = MUSB_EP0_STAGE_IDLE;
 		break;
 	}
 
@@ -959,7 +992,7 @@ static int musb_g_ep0_halt(struct usb_ep *e, int value)
 
 		csr |= MUSB_CSR0_P_SENDSTALL;
 		musb_writew(regs, MUSB_CSR0, csr);
-		musb->ep0_state = MUSB_EP0_STAGE_SETUP;
+		musb->ep0_state = MUSB_EP0_STAGE_IDLE;
 		musb->ackpend = 0;
 		break;
 	default: