svn commit: r259248 - head/sys/dev/usb/controller

[Hans Petter Selasky]

Author: hselasky
Date: Thu Dec 12 08:34:51 2013
New Revision: 259248
URL: http://svnweb.freebsd.org/changeset/base/259248

Log:
  Set chain bit correctly. This will fix some problems sending and
  receiving Zero Length Packets, ZLPs. See comment in code for more
  information.
  
  MFC after:	1 week
  Reported by:	Kohji Okuno <okuno.kohji at jp.panasonic.com>

Modified:
  head/sys/dev/usb/controller/xhci.c

Modified: head/sys/dev/usb/controller/xhci.c
==============================================================================
--- head/sys/dev/usb/controller/xhci.c	Thu Dec 12 08:23:28 2013	(r259247)
+++ head/sys/dev/usb/controller/xhci.c	Thu Dec 12 08:34:51 2013	(r259248)
@@ -1892,7 +1892,16 @@ restart:
 		td->td_trb[x].dwTrb2 = htole32(dword);
 
 		dword = XHCI_TRB_3_TYPE_SET(XHCI_TRB_TYPE_LINK) |
-		    XHCI_TRB_3_CYCLE_BIT | XHCI_TRB_3_IOC_BIT;
+		    XHCI_TRB_3_CYCLE_BIT | XHCI_TRB_3_IOC_BIT |
+		    /*
+		     * CHAIN-BIT: Ensure that a multi-TRB IN-endpoint
+		     * frame only receives a single short packet event
+		     * by setting the CHAIN bit in the LINK field. In
+		     * addition some XHCI controllers have problems
+		     * sending a ZLP unless the CHAIN-BIT is set in
+		     * the LINK TRB.
+		     */
+		    XHCI_TRB_3_CHAIN_BIT;
 
 		td->td_trb[x].dwTrb3 = htole32(dword);
 
@@ -1930,7 +1939,7 @@ restart:
 	}
 
 	/* clear TD SIZE to zero, hence this is the last TRB */
-	/* remove chain bit because this is the last TRB in the chain */
+	/* remove chain bit because this is the last data TRB in the chain */
 	td->td_trb[td->ntrb - 1].dwTrb2 &= ~htole32(XHCI_TRB_2_TDSZ_SET(15));
 	td->td_trb[td->ntrb - 1].dwTrb3 &= ~htole32(XHCI_TRB_3_CHAIN_BIT);