From 7bb9b7d36fa457a9fc463108d1228fd318891da4 Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.org>
Date: Thu, 11 Jul 2019 17:55:43 +0100
Subject: [PATCH] xhci: add quirk for host controllers that don't
 update endpoint DCS

Seen on a VLI VL805 PCIe to USB controller. For non-stream endpoints
at least, if the xHC halts on a particular TRB due to an error then
the DCS field in the Out Endpoint Context maintained by the hardware
is not updated with the current cycle state.

Using the quirk XHCI_EP_CTX_BROKEN_DCS and instead fetch the DCS bit
from the TRB that the xHC stopped on.

See: https://github.com/raspberrypi/linux/issues/3060

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.org>
---
 drivers/usb/host/xhci-pci.c  |  4 +++-
 drivers/usb/host/xhci-ring.c | 26 +++++++++++++++++++++++++-
 drivers/usb/host/xhci.h      |  1 +
 3 files changed, 29 insertions(+), 2 deletions(-)

--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -258,8 +258,10 @@ static void xhci_pci_quirks(struct devic
 		xhci->quirks |= XHCI_BROKEN_STREAMS;
 
 	if (pdev->vendor == PCI_VENDOR_ID_VIA &&
-			pdev->device == 0x3483)
+			pdev->device == 0x3483) {
 		xhci->quirks |= XHCI_LPM_SUPPORT;
+		xhci->quirks |= XHCI_EP_CTX_BROKEN_DCS;
+	}
 
 	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
@@ -527,7 +527,10 @@ void xhci_find_new_dequeue_state(struct
 	struct xhci_virt_ep *ep = &dev->eps[ep_index];
 	struct xhci_ring *ep_ring;
 	struct xhci_segment *new_seg;
+	struct xhci_segment *halted_seg = NULL;
 	union xhci_trb *new_deq;
+	union xhci_trb *halted_trb;
+	int index = 0;
 	dma_addr_t addr;
 	u64 hw_dequeue;
 	bool cycle_found = false;
@@ -565,7 +568,28 @@ void xhci_find_new_dequeue_state(struct
 	hw_dequeue = xhci_get_hw_deq(xhci, dev, ep_index, stream_id);
 	new_seg = ep_ring->deq_seg;
 	new_deq = ep_ring->dequeue;
-	state->new_cycle_state = hw_dequeue & 0x1;
+
+	/*
+	 * Quirk: xHC write-back of the DCS field in the hardware dequeue
+	 * pointer is wrong - use the cycle state of the TRB pointed to by
+	 * the dequeue pointer.
+	 */
+	if (xhci->quirks & XHCI_EP_CTX_BROKEN_DCS &&
+	    !(ep->ep_state & EP_HAS_STREAMS))
+		halted_seg = trb_in_td(xhci, cur_td->start_seg,
+				       cur_td->first_trb, cur_td->last_trb,
+				       hw_dequeue & ~0xf, false);
+	if (halted_seg) {
+		index = ((dma_addr_t)(hw_dequeue & ~0xf) - halted_seg->dma) /
+			 sizeof(*halted_trb);
+		halted_trb = &halted_seg->trbs[index];
+		state->new_cycle_state = halted_trb->generic.field[3] & 0x1;
+		xhci_dbg(xhci, "Endpoint DCS = %d TRB index = %d cycle = %d\n",
+			 (u8)(hw_dequeue & 0x1), index,
+			 state->new_cycle_state);
+	} else {
+		state->new_cycle_state = hw_dequeue & 0x1;
+	}
 	state->stream_id = stream_id;
 
 	/*
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1873,6 +1873,7 @@ struct xhci_hcd {
 #define XHCI_DEFAULT_PM_RUNTIME_ALLOW	BIT_ULL(33)
 #define XHCI_RESET_PLL_ON_DISCONNECT	BIT_ULL(34)
 #define XHCI_SNPS_BROKEN_SUSPEND    BIT_ULL(35)
+#define XHCI_EP_CTX_BROKEN_DCS	BIT_ULL(36)
 #define XHCI_SKIP_PHY_INIT	BIT_ULL(37)
 #define XHCI_DISABLE_SPARSE	BIT_ULL(38)
 #define XHCI_NO_SOFT_RETRY	BIT_ULL(40)
