releases/3.4.49/usb-revert-periodic-scheduling-bugfix.patch

   1 From fdc03438f53a00294ed9939eb3a1f6db6f3d8963 Mon Sep 17 00:00:00 2001
   2 From: Alan Stern <stern@rowland.harvard.edu>
   3 Date: Tue, 28 May 2013 14:03:10 -0400
   4 Subject: USB: revert periodic scheduling bugfix
   5
   6 From: Alan Stern <stern@rowland.harvard.edu>
   7
   8 commit fdc03438f53a00294ed9939eb3a1f6db6f3d8963 upstream.
   9
  10 This patch reverts commit 3e619d04159be54b3daa0b7036b0ce9e067f4b5d
  11 (USB: EHCI: fix bug in scheduling periodic split transfers).  The
  12 commit was valid -- it fixed a real bug -- but the periodic scheduler
  13 in ehci-hcd is in such bad shape (especially the part that handles
  14 split transactions) that fixing one bug is very likely to cause
  15 another to surface.  That's what happened in this case; the result was
  16 choppy and noisy playback on certain 24-bit audio devices.
  17
  18 The only real fix will be to rewrite this entire section of code.  My
  19 next project...
  20
  21 This fixes https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1136110.
  22
  23 Thanks to Tim Richardson for extra testing and feedback, and to Joseph
  24 Salisbury and Tyson Tan for tracking down the original source of the
  25 problem.
  26
  27 Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
  28 CC: Joseph Salisbury <joseph.salisbury@canonical.com>
  29 CC: Tim Richardson <tim@tim-richardson.net>
  30 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  31
  32 ---
  33  drivers/usb/host/ehci-sched.c |    2 +-
  34  1 file changed, 1 insertion(+), 1 deletion(-)
  35
  36 --- a/drivers/usb/host/ehci-sched.c
  37 +++ b/drivers/usb/host/ehci-sched.c
  38 @@ -236,7 +236,7 @@ static inline unsigned char tt_start_ufr
  39  }
  40
  41  static const unsigned char
  42 -max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 125, 25 };
  43 +max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 30, 0 };
  44
  45  /* carryover low/fullspeed bandwidth that crosses uframe boundries */
  46  static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])