xHCI: fix bug in xhci_clear_command_ring()

When system enters suspend, xHCI driver clears command ring by writing zero
to all the TRBs. However, this also writes zero to the Link TRB, and the ring
is mangled. This may cause driver accesses wrong memory address and the
result is unpredicted.

When clear the command ring, keep the last Link TRB intact, only clear its
cycle bit. This should fix the "command ring full" issue reported by Oliver
Neukum.

This should be backported to stable kernels as old as 2.6.37, since the
commit 89821320 "xhci: Fix command ring replay after resume" is merged.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reported-by: Oliver Neukum <oneukum@suse.de>

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index aa94c01957919001e6a5804c7bc0434b923f20bc..a1afb7c39f7e70c36c12a8bccdc0a0b64b7f29d3 100644 (file)
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -711,7 +711,10 @@ static void xhci_clear_command_ring(struct xhci_hcd *xhci)
        ring = xhci->cmd_ring;
        seg = ring->deq_seg;
        do {
-               memset(seg->trbs, 0, SEGMENT_SIZE);
+               memset(seg->trbs, 0,
+                       sizeof(union xhci_trb) * (TRBS_PER_SEGMENT - 1));
+               seg->trbs[TRBS_PER_SEGMENT - 1].link.control &=
+                       cpu_to_le32(~TRB_CYCLE);
                seg = seg->next;
        } while (seg != ring->deq_seg);