[PATCH 4.4 008/101] usb: musb: core: add clear_ep_rxintr() to musb_platform_ops

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bin Liu <b-liu@ti.com>

commit 6def85a396ce7796bd9f4561c6ae8138833f7a52 upstream.

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+.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/musb/musb_core.h |    7 +++++++
 drivers/usb/musb/musb_host.c |   10 ++++------
 2 files changed, 11 insertions(+), 6 deletions(-)

--- a/drivers/usb/musb/musb_core.h
+++ b/drivers/usb/musb/musb_core.h
@@ -214,6 +214,7 @@ struct musb_platform_ops {
 				dma_addr_t *dma_addr, u32 *len);
 	void	(*pre_root_reset_end)(struct musb *musb);
 	void	(*post_root_reset_end)(struct musb *musb);
+	void	(*clear_ep_rxintr)(struct musb *musb, int epnum);
 };
 
 /*
@@ -612,4 +613,10 @@ static inline void musb_platform_post_ro
 		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);
+}
+
 #endif	/* __MUSB_CORE_H__ */
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -2390,12 +2390,11 @@ static int musb_cleanup_urb(struct urb *
 	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);
@@ -2412,10 +2411,9 @@ static int musb_cleanup_urb(struct urb *
 		/* 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);