usb: musb: use is_host_active() to distinguish between host and gadget mode

On AM33xx platforms, unplugging a device in the middle of an active
transfer leads to a drop of MUSB_DEVCTL_HM in MUSB_DEVCTL before the
system is informed about a disconnect. This consequently makes the musb
core call the gadget code to handle the interrupt request, which then
crashes the kernel because the relevant pointers haven't been set up
for gadget mode.

To fix this, use is_host_active() rather than (devctl & MUSB_DEVCTL_HM)
in musb_interrupt() and musb_dma_completion() to detect whether the
controller is in host or peripheral mode. This information is provided
by the driver logic and does not rely on register contents.
Signed-off-by: NDaniel Mack <zonque@gmail.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_core.c

@@ -1517,7 +1517,7 @@ irqreturn_t musb_interrupt(struct musb *musb)
 	devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
 
 	dev_dbg(musb->controller, "** IRQ %s usb%04x tx%04x rx%04x\n",
-		(devctl & MUSB_DEVCTL_HM) ? "host" : "peripheral",
+		is_host_active(musb) ? "host" : "peripheral",
 		musb->int_usb, musb->int_tx, musb->int_rx);
 
 	/* the core can interrupt us for multiple reasons; docs have
@@ -1531,7 +1531,7 @@ irqreturn_t musb_interrupt(struct musb *musb)
 
 	/* handle endpoint 0 first */
 	if (musb->int_tx & 1) {
-		if (devctl & MUSB_DEVCTL_HM)
+		if (is_host_active(musb))
 			retval |= musb_h_ep0_irq(musb);
 		else
 			retval |= musb_g_ep0_irq(musb);
@@ -1545,7 +1545,7 @@ irqreturn_t musb_interrupt(struct musb *musb)
 			/* musb_ep_select(musb->mregs, ep_num); */
 			/* REVISIT just retval = ep->rx_irq(...) */
 			retval = IRQ_HANDLED;
-			if (devctl & MUSB_DEVCTL_HM)
+			if (is_host_active(musb))
 				musb_host_rx(musb, ep_num);
 			else
 				musb_g_rx(musb, ep_num);
@@ -1563,7 +1563,7 @@ irqreturn_t musb_interrupt(struct musb *musb)
 			/* musb_ep_select(musb->mregs, ep_num); */
 			/* REVISIT just retval |= ep->tx_irq(...) */
 			retval = IRQ_HANDLED;
-			if (devctl & MUSB_DEVCTL_HM)
+			if (is_host_active(musb))
 				musb_host_tx(musb, ep_num);
 			else
 				musb_g_tx(musb, ep_num);
@@ -1585,15 +1585,13 @@ MODULE_PARM_DESC(use_dma, "enable/disable use of DMA");
 
 void musb_dma_completion(struct musb *musb, u8 epnum, u8 transmit)
 {
-	u8	devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
-
 	/* called with controller lock already held */
 
 	if (!epnum) {
 #ifndef CONFIG_USB_TUSB_OMAP_DMA
 		if (!is_cppi_enabled()) {
 			/* endpoint 0 */
-			if (devctl & MUSB_DEVCTL_HM)
+			if (is_host_active(musb))
 				musb_h_ep0_irq(musb);
 			else
 				musb_g_ep0_irq(musb);
@@ -1602,13 +1600,13 @@ void musb_dma_completion(struct musb *musb, u8 epnum, u8 transmit)
 	} else {
 		/* endpoints 1..15 */
 		if (transmit) {
-			if (devctl & MUSB_DEVCTL_HM)
+			if (is_host_active(musb))
 				musb_host_tx(musb, epnum);
 			else
 				musb_g_tx(musb, epnum);
 		} else {
 			/* receive */
-			if (devctl & MUSB_DEVCTL_HM)
+			if (is_host_active(musb))
 				musb_host_rx(musb, epnum);
 			else
 				musb_g_rx(musb, epnum);