xHCI: fix bug in xhci_clear_command_ring()

commit 158886cd2cf4599e04f9b7e10cb767f5f39b14f1 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 1f0e198a865d0f558bbee5854b70554a61693421..221f14e1fddbfcc29542f5bbd853aaecf63965ae 100644 (file)
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -657,7 +657,10 @@ 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);