usb: musb: core: add clear_ep_rxintr() to musb_platform_ops

During dma teardown for dequque urb, if musb load is high, musb might
generate bogus rx ep interrupt even when the rx fifo is flushed. In such
case any of the follow log messages could happen.

	musb_host_rx 1853: BOGUS RX2 ready, csr 0000, count 0

	musb_host_rx 1936: RX3 dma busy, csr 2020

As mentioned in the current inline comment, clearing ep interrupt in the
teardown path avoids the bogus interrupt.

Clearing ep interrupt is platform dependent, so this patch adds a
platform callback to allow glue driver to clear the ep interrupt.

This bug seems to be existing since the initial driver for musb support,
but I only validated the fix back to v4.1, so only cc stable for v4.1+.

cc: stable@vger.kernel.org # 4.1+
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_core.h

@@ -216,6 +216,7 @@ struct musb_platform_ops {
 	void	(*pre_root_reset_end)(struct musb *musb);
 	void	(*post_root_reset_end)(struct musb *musb);
 	int	(*phy_callback)(enum musb_vbus_id_status status);
+	void	(*clear_ep_rxintr)(struct musb *musb, int epnum);
 };
 
 /*
@@ -626,6 +627,12 @@ static inline void musb_platform_post_root_reset_end(struct musb *musb)
 		musb->ops->post_root_reset_end(musb);
 }
 
+static inline void musb_platform_clear_ep_rxintr(struct musb *musb, int epnum)
+{
+	if (musb->ops->clear_ep_rxintr)
+		musb->ops->clear_ep_rxintr(musb, epnum);
+}
+
 /*
  * gets the "dr_mode" property from DT and converts it into musb_mode
  * if the property is not found or not recognized returns MUSB_OTG

drivers/usb/musb/musb_host.c

@@ -2374,12 +2374,11 @@ static int musb_cleanup_urb(struct urb *urb, struct musb_qh *qh)
 	int			is_in = usb_pipein(urb->pipe);
 	int			status = 0;
 	u16			csr;
+	struct dma_channel	*dma = NULL;
 
 	musb_ep_select(regs, hw_end);
 
 	if (is_dma_capable()) {
-		struct dma_channel	*dma;
-
 		dma = is_in ? ep->rx_channel : ep->tx_channel;
 		if (dma) {
 			status = ep->musb->dma_controller->channel_abort(dma);
@@ -2395,10 +2394,9 @@ static int musb_cleanup_urb(struct urb *urb, struct musb_qh *qh)
 		/* giveback saves bulk toggle */
 		csr = musb_h_flush_rxfifo(ep, 0);
 
-		/* REVISIT we still get an irq; should likely clear the
-		 * endpoint's irq status here to avoid bogus irqs.
-		 * clearing that status is platform-specific...
-		 */
+		/* clear the endpoint's irq status here to avoid bogus irqs */
+		if (is_dma_capable() && dma)
+			musb_platform_clear_ep_rxintr(musb, ep->epnum);
 	} else if (ep->epnum) {
 		musb_h_tx_flush_fifo(ep);
 		csr = musb_readw(epio, MUSB_TXCSR);