[PATCH 2/3] xhci: Fix control transfer error on Etron xHCI host

[Kuangyi Chiang <ki.chiang65@gmail.com>]

Performing a stability stress test on a USB3.0 2.5G ethernet adapter
results in errors like this:

[   91.441469] r8152 2-3:1.0 eth3: get_registers -71
[   91.458659] r8152 2-3:1.0 eth3: get_registers -71
[   91.475911] r8152 2-3:1.0 eth3: get_registers -71
[   91.493203] r8152 2-3:1.0 eth3: get_registers -71
[   91.510421] r8152 2-3:1.0 eth3: get_registers -71

The r8152 driver will periodically issue lots of control-IN requests
to access the status of ethernet adapter hardware registers during
the test.

This happens when the xHCI driver enqueue a control TD (which cross
over the Link TRB between two ring segments, as shown) in the endpoint
zero's transfer ring. Seems the Etron xHCI host can not perform this
TD correctly, causing the USB transfer error occurred, maybe the upper
driver retry that control-IN request can solve problem, but not all
drivers do this.

|     |
-------
| TRB | Setup Stage
-------
| TRB | Link
-------
-------
| TRB | Data Stage
-------
| TRB | Status Stage
-------
|     |

To work around this, the xHCI driver should enqueue a No Op TRB if
next available TRB is the Link TRB in the ring segment, this can
prevent the Setup and Data Stage TRB to be breaked by the Link TRB.

Add a new quirk flag XHCI_NO_BREAK_CTRL_TD to invoke the workaround
in xhci_queue_ctrl_tx().

Both EJ168 and EJ188 have the same problem, applying this patch then
the problem is gone.

Fixes: d0e96f5a71a0 ("USB: xhci: Control transfer support.")
Cc: <stable@vger.kernel.org>
Signed-off-by: Kuangyi Chiang <ki.chiang65@gmail.com>
---
 drivers/usb/host/xhci-pci.c  |  2 ++
 drivers/usb/host/xhci-ring.c | 13 +++++++++++++
 drivers/usb/host/xhci.h      |  1 +
 3 files changed, 16 insertions(+)

diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 2fa7f32c2bf9..dda873f3fee7 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -398,12 +398,14 @@ static void xhci_pci_quirks(struct device *dev, struct xhci_hcd *xhci)
 		xhci->quirks |= XHCI_RESET_ON_RESUME;
 		xhci->quirks |= XHCI_BROKEN_STREAMS;
 		xhci->quirks |= XHCI_NO_RESET_DEVICE;
+		xhci->quirks |= XHCI_NO_BREAK_CTRL_TD;
 	}
 	if (pdev->vendor == PCI_VENDOR_ID_ETRON &&
 			pdev->device == PCI_DEVICE_ID_EJ188) {
 		xhci->quirks |= XHCI_RESET_ON_RESUME;
 		xhci->quirks |= XHCI_BROKEN_STREAMS;
 		xhci->quirks |= XHCI_NO_RESET_DEVICE;
+		xhci->quirks |= XHCI_NO_BREAK_CTRL_TD;
 	}
 
 	if (pdev->vendor == PCI_VENDOR_ID_RENESAS &&
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 4ea2c3e072a9..1c387d4dc152 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3727,6 +3727,19 @@ int xhci_queue_ctrl_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	if (!urb->setup_packet)
 		return -EINVAL;
 
+	if (xhci->quirks & XHCI_NO_BREAK_CTRL_TD) {
+		/*
+		 * If next available TRB is the Link TRB in the ring segment then
+		 * enqueue a No Op TRB, this can prevent the Setup and Data Stage
+		 * TRB to be breaked by the Link TRB.
+		 */
+		if (trb_is_link(ep_ring->enqueue + 1)) {
+			field = TRB_TYPE(TRB_TR_NOOP) | ep_ring->cycle_state;
+			queue_trb(xhci, ep_ring, false, 0, 0,
+					TRB_INTR_TARGET(0), field);
+		}
+	}
+
 	/* 1 TRB for setup, 1 for status */
 	num_trbs = 2;
 	/*
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 1272d725270a..aedbe8fee8be 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1629,6 +1629,7 @@ struct xhci_hcd {
 #define XHCI_ZHAOXIN_HOST	BIT_ULL(46)
 #define XHCI_WRITE_64_HI_LO	BIT_ULL(47)
 #define XHCI_NO_RESET_DEVICE	BIT_ULL(48)
+#define XHCI_NO_BREAK_CTRL_TD	BIT_ULL(49)
 
 	unsigned int		num_active_eps;
 	unsigned int		limit_active_eps;
-- 
2.25.1