ush: ehci: initialize altnext pointers in QH

Section 4.10.2 "Advance Queue" of ehci-specification-for-usb.pdf specifies how an EHCI controller loads a new QTD for processing if the QH is not already marked as active. It states: ===== If the field Bytes to Transfer is not zero and the T-bit in the Alternate Next qTD Pointer is set to zero, then the host controller uses the Alternate Next qTD Pointer. Otherwise, the host controller uses the Next qTD Pointer. If Next qTD Pointer’s T-bit is set to a one, then the host controller exits this state and uses the horizontal pointer to the next schedule data structure. ===== Hence, we must ensure that the alternate next QTD pointer's T-bit (TERMINATE) is set, so the EHCI controller knows to use the next QTD pointer. Signed-off-by: Stephen Warren <swarren@nvidia.com>

ush: ehci: initialize altnext pointers in QH
Section 4.10.2 "Advance Queue" of ehci-specification-for-usb.pdf specifies how an EHCI controller loads a new QTD for processing if the QH is not already marked as active. It states: ===== If the field Bytes to Transfer is not zero and the T-bit in the Alternate Next qTD Pointer is set to zero, then the host controller uses the Alternate Next qTD Pointer. Otherwise, the host controller uses the Next qTD Pointer. If Next qTD Pointer’s T-bit is set to a one, then the host controller exits this state and uses the horizontal pointer to the next schedule data structure. ===== Hence, we must ensure that the alternate next QTD pointer's T-bit (TERMINATE) is set, so the EHCI controller knows to use the next QTD pointer. Signed-off-by: Stephen Warren <swarren@nvidia.com>
Stephen Warren · Marek Vasut
1 parent 247161b816
Showing 1 changed file with 2 additions and 0 deletions Side-by-side Diff
drivers/usb/host/ehci-hcd.c
@@ -395,6 +395,7 @@
 		QH_ENDPT2_UFCMASK(0) | QH_ENDPT2_UFSMASK(0);
 	qh->qh_endpt2 = cpu_to_hc32(endpt);
 	qh->qh_overlay.qt_next = cpu_to_hc32(QT_NEXT_TERMINATE);
+	qh->qh_overlay.qt_altnext = cpu_to_hc32(QT_NEXT_TERMINATE);
  
 	tdp = &qh->qh_overlay.qt_next;
  
@@ -1186,6 +1187,7 @@
 			qh->qh_link = QH_LINK_TERMINATE;
  
 		qh->qh_overlay.qt_next = (uint32_t)td;
+		qh->qh_overlay.qt_altnext = QT_NEXT_TERMINATE;
 		qh->qh_endpt1 = (0 << 28) | /* No NAK reload (ehci 4.9) */
 			(usb_maxpacket(dev, pipe) << 16) | /* MPS */
 			(1 << 14) |
...	...	@@ -395,6 +395,7 @@
395	395	QH_ENDPT2_UFCMASK(0) \| QH_ENDPT2_UFSMASK(0);
396	396	qh->qh_endpt2 = cpu_to_hc32(endpt);
397	397	qh->qh_overlay.qt_next = cpu_to_hc32(QT_NEXT_TERMINATE);
	398	+ qh->qh_overlay.qt_altnext = cpu_to_hc32(QT_NEXT_TERMINATE);
398	399
399	400	tdp = &qh->qh_overlay.qt_next;
400	401
...	...	@@ -1186,6 +1187,7 @@
1186	1187	qh->qh_link = QH_LINK_TERMINATE;
1187	1188
1188	1189	qh->qh_overlay.qt_next = (uint32_t)td;
	1190	+ qh->qh_overlay.qt_altnext = QT_NEXT_TERMINATE;
1189	1191	qh->qh_endpt1 = (0 << 28) \| /* No NAK reload (ehci 4.9) */
1190	1192	(usb_maxpacket(dev, pipe) << 16) \| /* MPS */
1191	1193	(1 << 14) \|