xHCI: AMD isoc link TRB chain bit quirk

commit 7e393a834b41001174a8fb3ae3bc23a749467760 upstream.

Setting the chain (CH) bit in the link TRB of isochronous transfer rings
is required by AMD 0.96 xHCI host controller to successfully transverse
multi-TRB TD that span through different memory segments.

When a Missed Service Error event occurs, if the chain bit is not set in
the link TRB and the host skips TDs which just across a link TRB, the
host may falsely recognize the link TRB as a normal TRB. You can see
this may cause big trouble - the host does not jump to the right address
which is pointed by the link TRB, but continue fetching the memory which
is after the link TRB address, which may not even belong to the host,
and the result cannot be predicted.

This causes some big problems. Without the former patch I sent: "xHCI:
prevent infinite loop when processing MSE event", the system may hang.
With that patch applied, system does not hang, but the host still access
wrong memory address and isoc transfer will fail. With this patch,
isochronous transfer works as expected.

This patch should be applied to kernels as old as 2.6.36, which was when
the first isochronous support was added for the xHCI host controller.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 18 insertions, 14 deletions

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index d16870460493..104620b3764b 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -81,7 +81,7 @@ static void xhci_segment_free(struct xhci_hcd *xhci, struct xhci_segment *seg)
  * related flags, such as End TRB, Toggle Cycle, and no snoop.
  */
 static void xhci_link_segments(struct xhci_hcd *xhci, struct xhci_segment *prev,
-		struct xhci_segment *next, bool link_trbs)
+		struct xhci_segment *next, bool link_trbs, bool isoc)
 {
 	u32 val;
 
@@ -97,7 +97,9 @@ static void xhci_link_segments(struct xhci_hcd *xhci, struct xhci_segment *prev,
 		val &= ~TRB_TYPE_BITMASK;
 		val |= TRB_TYPE(TRB_LINK);
 		/* Always set the chain bit with 0.95 hardware */
-		if (xhci_link_trb_quirk(xhci))
+		/* Set chain bit for isoc rings on AMD 0.96 host */
+		if (xhci_link_trb_quirk(xhci) ||
+				(isoc && (xhci->quirks & XHCI_AMD_0x96_HOST)))
 			val |= TRB_CHAIN;
 		prev->trbs[TRBS_PER_SEGMENT-1].link.control = cpu_to_le32(val);
 	}
@@ -154,7 +156,7 @@ static void xhci_initialize_ring_info(struct xhci_ring *ring)
  * See section 4.9.1 and figures 15 and 16.
  */
 static struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
-		unsigned int num_segs, bool link_trbs, gfp_t flags)
+		unsigned int num_segs, bool link_trbs, bool isoc, gfp_t flags)
 {
 	struct xhci_ring	*ring;
 	struct xhci_segment	*prev;
@@ -180,12 +182,12 @@ static struct xhci_ring *xhci_ring_alloc(struct xhci_hcd *xhci,
 		next = xhci_segment_alloc(xhci, flags);
 		if (!next)
 			goto fail;
-		xhci_link_segments(xhci, prev, next, link_trbs);
+		xhci_link_segments(xhci, prev, next, link_trbs, isoc);
 
 		prev = next;
 		num_segs--;
 	}
-	xhci_link_segments(xhci, prev, ring->first_seg, link_trbs);
+	xhci_link_segments(xhci, prev, ring->first_seg, link_trbs, isoc);
 
 	if (link_trbs) {
 		/* See section 4.9.2.1 and 6.4.4.1 */
@@ -231,14 +233,14 @@ void xhci_free_or_cache_endpoint_ring(struct xhci_hcd *xhci,
  * pointers to the beginning of the ring.
  */
 static void xhci_reinit_cached_ring(struct xhci_hcd *xhci,
-		struct xhci_ring *ring)
+		struct xhci_ring *ring, bool isoc)
 {
 	struct xhci_segment	*seg = ring->first_seg;
 	do {
 		memset(seg->trbs, 0,
 				sizeof(union xhci_trb)*TRBS_PER_SEGMENT);
 		/* All endpoint rings have link TRBs */
-		xhci_link_segments(xhci, seg, seg->next, 1);
+		xhci_link_segments(xhci, seg, seg->next, 1, isoc);
 		seg = seg->next;
 	} while (seg != ring->first_seg);
 	xhci_initialize_ring_info(ring);
@@ -542,7 +544,7 @@ struct xhci_stream_info *xhci_alloc_stream_info(struct xhci_hcd *xhci,
 	 */
 	for (cur_stream = 1; cur_stream < num_streams; cur_stream++) {
 		stream_info->stream_rings[cur_stream] =
-			xhci_ring_alloc(xhci, 1, true, mem_flags);
+			xhci_ring_alloc(xhci, 1, true, false, mem_flags);
 		cur_ring = stream_info->stream_rings[cur_stream];
 		if (!cur_ring)
 			goto cleanup_rings;
@@ -767,7 +769,7 @@ int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
 	}
 
 	/* Allocate endpoint 0 ring */
-	dev->eps[0].ring = xhci_ring_alloc(xhci, 1, true, flags);
+	dev->eps[0].ring = xhci_ring_alloc(xhci, 1, true, false, flags);
 	if (!dev->eps[0].ring)
 		goto fail;
 
@@ -1177,10 +1179,10 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
 	 */
 	if (usb_endpoint_xfer_isoc(&ep->desc))
 		virt_dev->eps[ep_index].new_ring =
-			xhci_ring_alloc(xhci, 8, true, mem_flags);
+			xhci_ring_alloc(xhci, 8, true, true, mem_flags);
 	else
 		virt_dev->eps[ep_index].new_ring =
-			xhci_ring_alloc(xhci, 1, true, mem_flags);
+			xhci_ring_alloc(xhci, 1, true, false, mem_flags);
 	if (!virt_dev->eps[ep_index].new_ring) {
 		/* Attempt to use the ring cache */
 		if (virt_dev->num_rings_cached == 0)
@@ -1189,7 +1191,8 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
 			virt_dev->ring_cache[virt_dev->num_rings_cached];
 		virt_dev->ring_cache[virt_dev->num_rings_cached] = NULL;
 		virt_dev->num_rings_cached--;
-		xhci_reinit_cached_ring(xhci, virt_dev->eps[ep_index].new_ring);
+		xhci_reinit_cached_ring(xhci, virt_dev->eps[ep_index].new_ring,
+			usb_endpoint_xfer_isoc(&ep->desc) ? true : false);
 	}
 	virt_dev->eps[ep_index].skip = false;
 	ep_ring = virt_dev->eps[ep_index].new_ring;
@@ -2003,7 +2006,7 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
 		goto fail;
 
 	/* Set up the command ring to have one segments for now. */
-	xhci->cmd_ring = xhci_ring_alloc(xhci, 1, true, flags);
+	xhci->cmd_ring = xhci_ring_alloc(xhci, 1, true, false, flags);
 	if (!xhci->cmd_ring)
 		goto fail;
 	xhci_dbg(xhci, "Allocated command ring at %p\n", xhci->cmd_ring);
@@ -2034,7 +2037,8 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
 	 * the event ring segment table (ERST).  Section 4.9.3.
 	 */
 	xhci_dbg(xhci, "// Allocating event ring\n");
-	xhci->event_ring = xhci_ring_alloc(xhci, ERST_NUM_SEGS, false, flags);
+	xhci->event_ring = xhci_ring_alloc(xhci, ERST_NUM_SEGS, false, false,
+						flags);
 	if (!xhci->event_ring)
 		goto fail;
 	if (xhci_check_trb_in_td_math(xhci, flags) < 0)