From 4dccc6e881f1e8d93c895a4b89e266d79e2746df Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.org>
Date: Mon, 26 Oct 2020 14:03:35 +0000
Subject: [PATCH] xhci: quirks: add link TRB quirk for VL805

The VL805 controller can't cope with the TR Dequeue Pointer for an endpoint
being set to a Link TRB. The hardware-maintained endpoint context ends up
stuck at the address of the Link TRB, leading to erroneous ring expansion
events whenever the enqueue pointer wraps to the dequeue position.

If the search for the end of the current TD and ring cycle state lands on
a Link TRB, move to the next segment.

See: https://github.com/raspberrypi/linux/issues/3919

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
---
 drivers/usb/host/xhci-pci.c  | 1 +
 drivers/usb/host/xhci-ring.c | 9 +++++++++
 drivers/usb/host/xhci.h      | 1 +
 3 files changed, 11 insertions(+)

--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -294,8 +294,10 @@ static void xhci_pci_quirks(struct devic
 			pdev->device == 0x3432)
 		xhci->quirks |= XHCI_BROKEN_STREAMS;
 
-	if (pdev->vendor == PCI_VENDOR_ID_VIA && pdev->device == 0x3483)
+	if (pdev->vendor == PCI_VENDOR_ID_VIA && pdev->device == 0x3483) {
 		xhci->quirks |= XHCI_LPM_SUPPORT;
+		xhci->quirks |= XHCI_AVOID_DQ_ON_LINK;
+	}
 
 	if (pdev->vendor == PCI_VENDOR_ID_ASMEDIA &&
 		pdev->device == PCI_DEVICE_ID_ASMEDIA_1042_XHCI) {
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -664,6 +664,15 @@ static int xhci_move_dequeue_past_td(str
 	} while (!cycle_found || !td_last_trb_found);
 
 deq_found:
+	/*
+	 * Quirk: the xHC does not correctly parse link TRBs if the HW Dequeue
+	 * pointer is set to one. Advance to the next TRB (and next segment).
+	 */
+	if (xhci->quirks & XHCI_AVOID_DQ_ON_LINK && trb_is_link(new_deq)) {
+		if (link_trb_toggles_cycle(new_deq))
+			new_cycle ^= 0x1;
+		next_trb(xhci, ep_ring, &new_seg, &new_deq);
+	}
 
 	/* Don't update the ring cycle state for the producer (us). */
 	addr = xhci_trb_virt_to_dma(new_seg, new_deq);
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1907,6 +1907,7 @@ struct xhci_hcd {
 #define XHCI_RESET_TO_DEFAULT	BIT_ULL(44)
 #define XHCI_ZHAOXIN_TRB_FETCH	BIT_ULL(45)
 #define XHCI_ZHAOXIN_HOST	BIT_ULL(46)
+#define XHCI_AVOID_DQ_ON_LINK	BIT_ULL(47)
 
 	unsigned int		num_active_eps;
 	unsigned int		limit_active_eps;
