[PATCH v2] usb: musb: return -ESHUTDOWN in urb when three-strikes error happened

[Bin Liu <b-liu@ti.com>]

When a USB device attached to a hub got disconnected, MUSB controller
generates RXCSR_RX_ERROR interrupt for the 3-strikes-out error.

Currently the MUSB host driver returns -EPROTO in current URB, then the
USB device driver could immediately resubmit the URB which causes MUSB
generate RXCSR_RX_ERROR interrupt again. This circle causes interrupt
storm then the hub never got a chance to report the USB device detach.

To fix the interrupt storm, change the URB return code to -ESHUTDOWN for
MUSB_RXCSR_H_ERROR interrupt, so that the USB device driver will not
immediately resubmit the URB.

Signed-off-by: Bin Liu <b-liu@ti.com>
---
v2: added inline comments

 drivers/usb/musb/musb_host.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 8736f4251a22..8b7d22a0c0fb 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -1774,9 +1774,15 @@ void musb_host_rx(struct musb *musb, u8 epnum)
 		status = -EPIPE;
 
 	} else if (rx_csr & MUSB_RXCSR_H_ERROR) {
-		musb_dbg(musb, "end %d RX proto error", epnum);
+		dev_err(musb->controller, "ep%d RX three-strikes error", epnum);
 
-		status = -EPROTO;
+		/*
+		 * The three-strikes error could only happen when the USB
+		 * device is not accessible, for example detached or powered
+		 * off. So return the fatal error -ESHUTDOWN so hopefully the
+		 * USB device drivers won't immediately resubmit the same URB.
+		 */
+		status = -ESHUTDOWN;
 		musb_writeb(epio, MUSB_RXINTERVAL, 0);
 
 		rx_csr &= ~MUSB_RXCSR_H_ERROR;
-- 
2.17.1