USB: omap_udc: workaround dma_free_coherent() bogosity

Various fixes to omap_udc, noted with some recent testing:

 - Cope with some SMP-induced braindamage in ARM's dma_{alloc,free}_coherent()
   implementation: alloc() can be called with IRQs blocked, but since late
   last year that's no longer true for free().  This resolves really NASTY
   problems with logspamming via WARN_ON(), indicating N-page leaks.

 - Be more correct in handling GET_STATUS request for RECIP_ENDPOINT ... the
   previous code only handled RECIP_INTERFACE, this version should be correct
   except for (sigh) bulk/interrupt endpoints.

 - Provide a better name for the function reporting whether the board has
   vbus sensing wired up.

GET_STATUS requests for endpoint status still acts strangely though, at least
given one flakey host doesn't always ack the first DATA packet, then the packet
that gets retransmitted doesn't have data!
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/omap_udc.c

@@ -296,6 +296,15 @@ omap_free_request(struct usb_ep *ep, struct usb_request *_req)
 
 /*-------------------------------------------------------------------------*/
 
+/*
+ * dma-coherent memory allocation (for dma-capable endpoints)
+ *
+ * NOTE: the dma_*_coherent() API calls suck.  Most implementations are
+ * (a) page-oriented, so small buffers lose big; and (b) asymmetric with
+ * respect to calls with irqs disabled:  alloc is safe, free is not.
+ * We currently work around (b), but not (a).
+ */
+
 static void *
 omap_alloc_buffer(
 	struct usb_ep	*_ep,
@@ -307,6 +316,9 @@ omap_alloc_buffer(
 	void		*retval;
 	struct omap_ep	*ep;
 
+	if (!_ep)
+		return NULL;
+
 	ep = container_of(_ep, struct omap_ep, ep);
 	if (use_dma && ep->has_dma) {
 		static int	warned;
@@ -326,6 +338,35 @@ omap_alloc_buffer(
 	return retval;
 }
 
+static DEFINE_SPINLOCK(buflock);
+static LIST_HEAD(buffers);
+
+struct free_record {
+	struct list_head	list;
+	struct device		*dev;
+	unsigned		bytes;
+	dma_addr_t		dma;
+};
+
+static void do_free(unsigned long ignored)
+{
+	spin_lock_irq(&buflock);
+	while (!list_empty(&buffers)) {
+		struct free_record	*buf;
+
+		buf = list_entry(buffers.next, struct free_record, list);
+		list_del(&buf->list);
+		spin_unlock_irq(&buflock);
+
+		dma_free_coherent(buf->dev, buf->bytes, buf, buf->dma);
+
+		spin_lock_irq(&buflock);
+	}
+	spin_unlock_irq(&buflock);
+}
+
+static DECLARE_TASKLET(deferred_free, do_free, 0);
+
 static void omap_free_buffer(
 	struct usb_ep	*_ep,
 	void		*buf,
@@ -333,13 +374,29 @@ static void omap_free_buffer(
 	unsigned	bytes
 )
 {
+	if (!_ep) {
+		WARN_ON(1);
+		return;
+	}
+
+	/* free memory into the right allocator */
+	if (dma != DMA_ADDR_INVALID) {
 		struct omap_ep		*ep;
+		struct free_record	*rec = buf;
+		unsigned long		flags;
 
 		ep = container_of(_ep, struct omap_ep, ep);
-	if (use_dma && _ep && ep->has_dma)
-		dma_free_coherent(ep->udc->gadget.dev.parent, bytes, buf, dma);
-	else
-		kfree (buf);
+
+		rec->dev = ep->udc->gadget.dev.parent;
+		rec->bytes = bytes;
+		rec->dma = dma;
+
+		spin_lock_irqsave(&buflock, flags);
+		list_add_tail(&rec->list, &buffers);
+		tasklet_schedule(&deferred_free);
+		spin_unlock_irqrestore(&buflock, flags);
+	} else
+		kfree(buf);
 }
 
 /*-------------------------------------------------------------------------*/
@@ -1691,12 +1748,38 @@ static void ep0_irq(struct omap_udc *udc, u16 irq_src)
 			udc->ep0_pending = 0;
 			break;
 		case USB_REQ_GET_STATUS:
+			/* USB_ENDPOINT_HALT status? */
+			if (u.r.bRequestType != (USB_DIR_IN|USB_RECIP_ENDPOINT))
+				goto intf_status;
+
+			/* ep0 never stalls */
+			if (!(w_index & 0xf))
+				goto zero_status;
+
+			/* only active endpoints count */
+			ep = &udc->ep[w_index & 0xf];
+			if (w_index & USB_DIR_IN)
+				ep += 16;
+			if (!ep->desc)
+				goto do_stall;
+
+			/* iso never stalls */
+			if (ep->bmAttributes == USB_ENDPOINT_XFER_ISOC)
+				goto zero_status;
+
+			/* FIXME don't assume non-halted endpoints!! */
+			ERR("%s status, can't report\n", ep->ep.name);
+			goto do_stall;
+
+intf_status:
 			/* return interface status.  if we were pedantic,
 			 * we'd detect non-existent interfaces, and stall.
 			 */
 			if (u.r.bRequestType
 					!= (USB_DIR_IN|USB_RECIP_INTERFACE))
 				goto delegate;
+
+zero_status:
 			/* return two zero bytes */
 			UDC_EP_NUM_REG = UDC_EP_SEL|UDC_EP_DIR;
 			UDC_DATA_REG = 0;
@@ -2068,7 +2151,7 @@ static irqreturn_t omap_udc_iso_irq(int irq, void *_dev)
 
 /*-------------------------------------------------------------------------*/
 
-static inline int machine_needs_vbus_session(void)
+static inline int machine_without_vbus_sense(void)
 {
 	return (machine_is_omap_innovator()
 		|| machine_is_omap_osk()
@@ -2156,7 +2239,7 @@ int usb_gadget_register_driver (struct usb_gadget_driver *driver)
 	/* boards that don't have VBUS sensing can't autogate 48MHz;
 	 * can't enter deep sleep while a gadget driver is active.
 	 */
-	if (machine_needs_vbus_session())
+	if (machine_without_vbus_sense())
 		omap_vbus_session(&udc->gadget, 1);
 
 done:
@@ -2179,7 +2262,7 @@ int usb_gadget_unregister_driver (struct usb_gadget_driver *driver)
 	if (udc->dc_clk != NULL)
 		omap_udc_enable_clock(1);
 
-	if (machine_needs_vbus_session())
+	if (machine_without_vbus_sense())
 		omap_vbus_session(&udc->gadget, 0);
 
 	if (udc->transceiver)
@@ -2822,7 +2905,7 @@ static int __init omap_udc_probe(struct platform_device *pdev)
 		hmc = HMC_1510;
 		type = "(unknown)";
 
-		if (machine_is_omap_innovator() || machine_is_sx1()) {
+		if (machine_without_vbus_sense()) {
 			/* just set up software VBUS detect, and then
 			 * later rig it so we always report VBUS.
 			 * FIXME without really sensing VBUS, we can't