[PATCH 16/33] usb: xhci: add xhci_initialize_ring_segments()

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

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

A ring consists of a list of segments, each containing a specific number of
TRBs. The xhci driver allocates and initializes ring segments and TRBs in
the same functions. This combined allocation and initialization process
leads to an issue where, after hibernation (S4 state), the xhci driver
frees all its memory and re-creates the rings, segments, and TRBs from
scratch.

Move all default ring segment initialization into function
xhci_initialize_ring_segments(). This function can be called to
reinitialize a ring without freeing and reallocating it.

Since xhci_alloc_segments_for_ring() no longer initializes segment TRBs,
xhci_initialize_ring_segments() is added to xhci_ring_expansion(). This
results in the last segment of the source ring having the 'LINK_TOGGLE'
bit set. Therefore, if the last source ring segment is not the last in
the destination ring, the 'LINK_TOGGLE' bit must be cleared.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci-mem.c | 41 +++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 41a5e67e1c4f..4295e9a4de50 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -113,6 +113,22 @@ static void xhci_set_link_trb(struct xhci_segment *seg, bool chain_links)
 	trb->link.segment_ptr = cpu_to_le64(seg->next->dma);
 }
 
+static void xhci_initialize_ring_segments(struct xhci_hcd *xhci, struct xhci_ring *ring)
+{
+	struct xhci_segment *seg;
+	bool chain_links;
+
+	if (ring->type == TYPE_EVENT)
+		return;
+
+	chain_links = xhci_link_chain_quirk(xhci, ring->type);
+	xhci_for_each_ring_seg(ring->first_seg, seg)
+		xhci_set_link_trb(seg, chain_links);
+
+	/* See section 4.9.2.1 and 6.4.4.1 */
+	ring->last_seg->trbs[TRBS_PER_SEGMENT - 1].link.control |= cpu_to_le32(LINK_TOGGLE);
+}
+
 /*
  * Link the src ring segments to the dst ring.
  * Set Toggle Cycle for the new ring if needed.
@@ -143,13 +159,13 @@ static void xhci_link_rings(struct xhci_hcd *xhci, struct xhci_ring *src, struct
 	dst->num_segs += src->num_segs;
 
 	if (dst->enq_seg == dst->last_seg) {
-		if (dst->type != TYPE_EVENT) {
+		if (dst->type != TYPE_EVENT)
 			dst->last_seg->trbs[TRBS_PER_SEGMENT-1].link.control
 				&= ~cpu_to_le32(LINK_TOGGLE);
-			src->last_seg->trbs[TRBS_PER_SEGMENT-1].link.control
-				|= cpu_to_le32(LINK_TOGGLE);
-		}
+
 		dst->last_seg = src->last_seg;
+	} else if (dst->type != TYPE_EVENT) {
+		src->last_seg->trbs[TRBS_PER_SEGMENT-1].link.control &= ~cpu_to_le32(LINK_TOGGLE);
 	}
 
 	for (seg = dst->enq_seg; seg != dst->last_seg; seg = seg->next)
@@ -315,9 +331,6 @@ static int xhci_alloc_segments_for_ring(struct xhci_hcd *xhci, struct xhci_ring
 {
 	struct xhci_segment *prev;
 	unsigned int num = 0;
-	bool chain_links;
-
-	chain_links = xhci_link_chain_quirk(xhci, ring->type);
 
 	prev = xhci_segment_alloc(xhci, ring->bounce_buf_len, num, flags);
 	if (!prev)
@@ -333,17 +346,12 @@ static int xhci_alloc_segments_for_ring(struct xhci_hcd *xhci, struct xhci_ring
 			goto free_segments;
 
 		prev->next = next;
-		if (ring->type != TYPE_EVENT)
-			xhci_set_link_trb(prev, chain_links);
 		prev = next;
 		num++;
 	}
 	ring->last_seg = prev;
 
 	ring->last_seg->next = ring->first_seg;
-	if (ring->type != TYPE_EVENT)
-		xhci_set_link_trb(prev, chain_links);
-
 	return 0;
 
 free_segments:
@@ -381,12 +389,7 @@ struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci, unsigned int num_segs,
 	if (ret)
 		goto fail;
 
-	/* Only event ring does not use link TRB */
-	if (type != TYPE_EVENT) {
-		/* See section 4.9.2.1 and 6.4.4.1 */
-		ring->last_seg->trbs[TRBS_PER_SEGMENT - 1].link.control |=
-			cpu_to_le32(LINK_TOGGLE);
-	}
+	xhci_initialize_ring_segments(xhci, ring);
 	xhci_initialize_ring_info(ring);
 	trace_xhci_ring_alloc(ring);
 	return ring;
@@ -424,6 +427,8 @@ int xhci_ring_expansion(struct xhci_hcd *xhci, struct xhci_ring *ring,
 	if (ret)
 		return -ENOMEM;
 
+	xhci_initialize_ring_segments(xhci, &new_ring);
+
 	if (ring->type == TYPE_STREAM) {
 		ret = xhci_update_stream_segment_mapping(ring->trb_address_map, ring,
 							 new_ring.first_seg, flags);
-- 
2.25.1