From f759fff2c1bf5d1506a3994c6e2d92d6fbb3f000 Mon Sep 17 00:00:00 2001 From: Jonathan Bell Date: Fri, 3 Dec 2021 14:32:05 +0000 Subject: [PATCH] xhci: correct room_on_ring() for cases where there is a single segment Don't calculate space based on the number of TRBs in the current segment, as it's OK to wrap to the start (and flip the cycle state bit). Signed-off-by: Jonathan Bell --- drivers/usb/host/xhci-ring.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -309,6 +309,12 @@ static inline int room_on_ring(struct xh return 0; if (ring->type != TYPE_COMMAND && ring->type != TYPE_EVENT) { + /* + * If the ring has a single segment the dequeue segment + * never changes, so don't use it as measure of free space. + */ + if (ring->num_segs == 1) + return ring->num_trbs_free >= num_trbs; num_trbs_in_deq_seg = ring->dequeue - ring->deq_seg->trbs; if (ring->num_trbs_free < num_trbs + num_trbs_in_deq_seg) return 0;