[PATCH 4/5] usb: xhci: xhci_bulk_tx: re-fetch ep_ctx after resetting a halted endpoint

[Stephano Cetola]

xhci_bulk_tx() reads the endpoint's context once at the top of the
function and reuses that same value both to decide whether to call
reset_ep() and, further down, to pass to prepare_ring(). reset_ep()
clears the halt by updating the endpoint's output context via DMA,
but the earlier ep_ctx read is never invalidated or refetched after
that, so prepare_ring() always sees the stale pre-reset
EP_STATE_HALTED value.

prepare_ring() rejects the transfer with -EINVAL, regardless of
whether reset_ep() actually succeeded. The USB keyboard driver's
poller treats any error other than -EAGAIN as fatal. One spurious
rejection is enough to stop it for good, and nothing calls
xhci_bulk_tx() again after that. The keyboard stays dead until the
next boot.

Signed-off-by: Stephano Cetola <stephano at cetola.net>
---
 drivers/usb/host/xhci-ring.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 522ac7c45f..a3b78052a4 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -705,8 +705,13 @@ int xhci_bulk_tx(struct usb_device *udev, unsigned long pipe,
 	 * the next transfer. It is the responsibility of the upper layer to
 	 * have dealt with whatever caused the error.
 	 */
-	if ((le32_to_cpu(ep_ctx->ep_info) & EP_STATE_MASK) == EP_STATE_HALTED)
+	if ((le32_to_cpu(ep_ctx->ep_info) & EP_STATE_MASK) == EP_STATE_HALTED) {
 		reset_ep(udev, ep_index);
+		/* reset_ep() updates the context via DMA. Re-fetch it here. */
+		xhci_inval_cache((uintptr_t)virt_dev->out_ctx->bytes,
+				 virt_dev->out_ctx->size);
+		ep_ctx = xhci_get_ep_ctx(ctrl, virt_dev->out_ctx, ep_index);
+	}
 
 	ring = virt_dev->eps[ep_index].ring;
 	/*

-- 
2.55.0