[src/trunk]: src/sys/dev/usb Add another XXX comment, I'm not in a postition ...

[dsl <dsl%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/db52d546eac3
branches:  trunk
changeset: 326048:db52d546eac3
user:      dsl <dsl%NetBSD.org@localhost>
date:      Thu Jan 16 20:55:56 2014 +0000

description:
Add another XXX comment, I'm not in a postition to fix the code.
The 'cycle' bit of a LINK trb must not be changed until the cycle bit
of the following trb has been set.

diffstat:

 sys/dev/usb/xhci.c |  11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diffs (39 lines):

diff -r 70ea07d6b1c4 -r db52d546eac3 sys/dev/usb/xhci.c
--- a/sys/dev/usb/xhci.c        Thu Jan 16 20:31:42 2014 +0000
+++ b/sys/dev/usb/xhci.c        Thu Jan 16 20:55:56 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: xhci.c,v 1.12 2013/12/14 16:03:04 jakllsch Exp $       */
+/*     $NetBSD: xhci.c,v 1.13 2014/01/16 20:55:56 dsl Exp $    */
 
 /*
  * Copyright (c) 2013 Jonathan A. Kollasch
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xhci.c,v 1.12 2013/12/14 16:03:04 jakllsch Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xhci.c,v 1.13 2014/01/16 20:55:56 dsl Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1629,6 +1629,11 @@
         * Arbitrary aligned LINK trb definitely fail on Ivy bridge.
         * The simple solution is not to allow a LINK trb in the middle
         * of anything - as here.
+        * XXX: (dsl) There are xhci controllers out there (eg some made by
+        * ASMedia) that seem to lock up if they process a LINK trb but
+        * cannot process the linked-to trb yet.
+        * The code should write the 'cycle' bit on the link trb AFTER
+        * adding the other trb.
         */
        if (ri + ntrbs >= (xr->xr_ntrb - 1)) {
                parameter = xhci_ring_trbp(xr, 0);
@@ -2671,7 +2676,7 @@
 
        parameter = DMAADDR(dma, 0);
        /*
-        * XXX: The physical buffer must not cross a 64k boundary.
+        * XXX: (dsl) The physical buffer must not cross a 64k boundary.
         * If the user supplied buffer crosses such a boundary then 2
         * (or more) TRB should be used.
         * If multiple TRB are used the td_size field must be set correctly.