target/linux/bcm27xx/patches-5.15/950-0601-xhci-correct-room_on_ring-for-cases-where-there-is-a.patch

   1 From f759fff2c1bf5d1506a3994c6e2d92d6fbb3f000 Mon Sep 17 00:00:00 2001
   2 From: Jonathan Bell <jonathan@raspberrypi.com>
   3 Date: Fri, 3 Dec 2021 14:32:05 +0000
   4 Subject: [PATCH] xhci: correct room_on_ring() for cases where there is
   5  a single segment
   6
   7 Don't calculate space based on the number of TRBs in the current segment,
   8 as it's OK to wrap to the start (and flip the cycle state bit).
   9
  10 Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
  11 ---
  12  drivers/usb/host/xhci-ring.c | 6 ++++++
  13  1 file changed, 6 insertions(+)
  14
  15 --- a/drivers/usb/host/xhci-ring.c
  16 +++ b/drivers/usb/host/xhci-ring.c
  17 @@ -289,6 +289,12 @@ static inline int room_on_ring(struct xh
  18                 return 0;
  19
  20         if (ring->type != TYPE_COMMAND && ring->type != TYPE_EVENT) {
  21 +               /*
  22 +                * If the ring has a single segment the dequeue segment
  23 +                * never changes, so don't use it as measure of free space.
  24 +                */
  25 +               if (ring->num_segs == 1)
  26 +                       return ring->num_trbs_free >= num_trbs;
  27                 num_trbs_in_deq_seg = ring->dequeue - ring->deq_seg->trbs;
  28                 if (ring->num_trbs_free < num_trbs + num_trbs_in_deq_seg)
  29                         return 0;