xHCI: count free TRBs on transfer ring
In the past, the room_on_ring() check was implemented by walking all over
the ring, which is wasteful and complicated.
Count the number of free TRBs instead. The free TRBs number should be
updated when enqueue/dequeue pointer is updated, or upon the completion
of a set dequeue pointer command.
Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Paul Zimmerman <Paul.Zimmerman@synopsys.com>
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index bdea4de..212012c 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -135,6 +135,12 @@
/* Not necessary for new rings, but needed for re-initialized rings */
ring->enq_updates = 0;
ring->deq_updates = 0;
+
+ /*
+ * Each segment has a link TRB, and leave an extra TRB for SW
+ * accounting purpose
+ */
+ ring->num_trbs_free = ring->num_segs * (TRBS_PER_SEGMENT - 1) - 1;
}
/**