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.c b/drivers/usb/host/xhci.c
index 262400c..dec5b2d 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -729,6 +729,7 @@
ring->enq_seg = ring->deq_seg;
ring->enqueue = ring->dequeue;
+ ring->num_trbs_free = ring->num_segs * (TRBS_PER_SEGMENT - 1) - 1;
/*
* Ring is now zeroed, so the HW should look for change of ownership
* when the cycle bit is set to 1.