[PATCH 4/6] usb: xhci: improve TR Dequeue Pointer mask

[Mathias Nyman <mathias.nyman@linux.intel.com>]

From: Niklas Neronin <niklas.neronin@linux.intel.com>

Address the naming and usage of the TR Dequeue Pointer mask in the xhci
driver. The Endpoint Context Field at offset 0x08 is defined as follows:
 Bit 0		Dequeue Cycle State (DCS)
 Bits 3:1	RsvdZ (Reserved and Zero)
 Bits 63:4	TR Dequeue Pointer

When extracting the TR Dequeue Pointer for an Endpoint without Streams,
in xhci_handle_cmd_set_deq(), the inverted Dequeue Cycle State mask
(~EP_CTX_CYCLE_MASK) is used, inadvertently including the Reserved bits.
Although bits 3:1 are typically zero, using the incorrect mask could cause
issues.

The existing mask, named "SCTX_DEQ_MASK," is misleading because "SCTX"
implies exclusivity to Stream Contexts, whereas the TR Dequeue Pointer is
applicable to both Stream and non-Stream Contexts.

Rename the mask to "TR_DEQ_PTR_MASK", utilize GENMASK_ULL() macro and use
the mask when handling the TR Dequeue Pointer field.

Function xhci_get_hw_deq() returns the Endpoint Context Field 0x08, either
directly from the Endpoint context or a Stream.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci-ring.c | 12 ++++++------
 drivers/usb/host/xhci.h      |  3 ++-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index e3d0e2e0312e..96c5bab9eb60 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -711,7 +711,7 @@ static int xhci_move_dequeue_past_td(struct xhci_hcd *xhci,
 		return -ENODEV;
 	}
 
-	hw_dequeue = xhci_get_hw_deq(xhci, dev, ep_index, stream_id);
+	hw_dequeue = xhci_get_hw_deq(xhci, dev, ep_index, stream_id) & TR_DEQ_PTR_MASK;
 	new_seg = ep_ring->deq_seg;
 	new_deq = ep_ring->dequeue;
 	new_cycle = le32_to_cpu(td->end_trb->generic.field[3]) & TRB_CYCLE;
@@ -723,7 +723,7 @@ static int xhci_move_dequeue_past_td(struct xhci_hcd *xhci,
 	 */
 	do {
 		if (!hw_dequeue_found && xhci_trb_virt_to_dma(new_seg, new_deq)
-		    == (dma_addr_t)(hw_dequeue & ~0xf)) {
+		    == (dma_addr_t)hw_dequeue) {
 			hw_dequeue_found = true;
 			if (td_last_trb_found)
 				break;
@@ -1066,7 +1066,7 @@ static int xhci_invalidate_cancelled_tds(struct xhci_virt_ep *ep)
 		 */
 		hw_deq = xhci_get_hw_deq(xhci, ep->vdev, ep->ep_index,
 					 td->urb->stream_id);
-		hw_deq &= ~0xf;
+		hw_deq &= TR_DEQ_PTR_MASK;
 
 		if (td->cancel_status == TD_HALTED || trb_in_td(td, hw_deq)) {
 			switch (td->cancel_status) {
@@ -1156,7 +1156,7 @@ static struct xhci_td *find_halted_td(struct xhci_virt_ep *ep)
 
 	if (!list_empty(&ep->ring->td_list)) { /* Not streams compatible */
 		hw_deq = xhci_get_hw_deq(ep->xhci, ep->vdev, ep->ep_index, 0);
-		hw_deq &= ~0xf;
+		hw_deq &= TR_DEQ_PTR_MASK;
 		td = list_first_entry(&ep->ring->td_list, struct xhci_td, td_list);
 		if (trb_in_td(td, hw_deq))
 			return td;
@@ -1479,7 +1479,7 @@ static void xhci_handle_cmd_set_deq(struct xhci_hcd *xhci, int slot_id,
 		u64 deq;
 		/* 4.6.10 deq ptr is written to the stream ctx for streams */
 		if (ep->ep_state & EP_HAS_STREAMS) {
-			deq = le64_to_cpu(stream_ctx->stream_ring) & SCTX_DEQ_MASK;
+			deq = le64_to_cpu(stream_ctx->stream_ring) & TR_DEQ_PTR_MASK;
 
 			/*
 			 * Cadence xHCI controllers store some endpoint state
@@ -1495,7 +1495,7 @@ static void xhci_handle_cmd_set_deq(struct xhci_hcd *xhci, int slot_id,
 				stream_ctx->reserved[1] = 0;
 			}
 		} else {
-			deq = le64_to_cpu(ep_ctx->deq) & ~EP_CTX_CYCLE_MASK;
+			deq = le64_to_cpu(ep_ctx->deq) & TR_DEQ_PTR_MASK;
 		}
 		xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
 			"Successful Set TR Deq Ptr cmd, deq = @%08llx", deq);
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 85d5b964bf1e..30f311d899c3 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -500,7 +500,8 @@ struct xhci_ep_ctx {
 
 /* deq bitmasks */
 #define EP_CTX_CYCLE_MASK		(1 << 0)
-#define SCTX_DEQ_MASK			(~0xfL)
+/* bits 63:4 - TR Dequeue Pointer */
+#define TR_DEQ_PTR_MASK			GENMASK_ULL(63, 4)
 
 
 /**
-- 
2.43.0