[ehci] Support USB1 devices attached via transaction translators

Support low-speed and full-speed devices attached to a USB2 hub.  Such
devices use a transaction translator (TT) within the USB2 hub, which
asynchronously initiates transactions on the lower-speed bus and
returns the result via a split completion on the high-speed bus.

We make the simplifying assumption that there will never be more than
sixteen active interrupt endpoints behind a single transaction
translator; this assumption allows us to schedule all periodic start
splits in microframe 0 and all periodic split completions in
microframes 2 and 3.  (We do not handle isochronous endpoints.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>

2 files changed, 53 insertions, 11 deletions

diff --git a/src/drivers/usb/ehci.c b/src/drivers/usb/ehci.c
index 83635f45..f912de35 100644
--- a/src/drivers/usb/ehci.c
+++ b/src/drivers/usb/ehci.c
@@ -545,7 +545,7 @@ static int ehci_enqueue ( struct ehci_device *ehci, struct ehci_ring *ring,
 		assert ( xfer->len <= EHCI_LEN_MASK );
 		assert ( EHCI_FL_TOGGLE == EHCI_LEN_TOGGLE );
 		desc->len = cpu_to_le16 ( xfer->len | toggle );
-		desc->flags = xfer->flags;
+		desc->flags = ( xfer->flags | EHCI_FL_CERR_MAX );
 
 		/* Copy data to immediate data buffer (if requested) */
 		data = xfer->data;
@@ -902,19 +902,16 @@ static uint32_t ehci_endpoint_characteristics ( struct usb_endpoint *ep ) {
 		chr |= EHCI_CHR_TOGGLE;
 
 	/* Determine endpoint speed */
-	switch ( usb->port->speed ) {
-	case USB_SPEED_HIGH :
+	if ( usb->port->speed == USB_SPEED_HIGH ) {
 		chr |= EHCI_CHR_EPS_HIGH;
-		break;
-	case USB_SPEED_FULL :
-		chr |= EHCI_CHR_EPS_FULL;
-		break;
-	default:
-		assert ( usb->port->speed == USB_SPEED_LOW );
-		chr |= EHCI_CHR_EPS_LOW;
+	} else {
+		if ( usb->port->speed == USB_SPEED_FULL ) {
+			chr |= EHCI_CHR_EPS_FULL;
+		} else {
+			chr |= EHCI_CHR_EPS_LOW;
+		}
 		if ( attr == USB_ENDPOINT_ATTR_CONTROL )
 			chr |= EHCI_CHR_CONTROL;
-		break;
 	}
 
 	return chr;
@@ -927,6 +924,8 @@ static uint32_t ehci_endpoint_characteristics ( struct usb_endpoint *ep ) {
  * @ret cap		Endpoint capabilities
  */
 static uint32_t ehci_endpoint_capabilities ( struct usb_endpoint *ep ) {
+	struct usb_device *usb = ep->usb;
+	struct usb_port *tt = usb_transaction_translator ( usb );
 	unsigned int attr = ( ep->attributes & USB_ENDPOINT_ATTR_TYPE_MASK );
 	uint32_t cap;
 	unsigned int i;
@@ -943,6 +942,15 @@ static uint32_t ehci_endpoint_capabilities ( struct usb_endpoint *ep ) {
 		}
 	}
 
+	/* Set transaction translator hub address and port, if applicable */
+	if ( tt ) {
+		assert ( tt->hub->usb );
+		cap |= ( EHCI_CAP_TT_HUB ( tt->hub->usb->address ) |
+			 EHCI_CAP_TT_PORT ( tt->address ) );
+		if ( attr == USB_ENDPOINT_ATTR_INTERRUPT )
+			cap |= EHCI_CAP_SPLIT_SCHED_DEFAULT;
+	}
+
 	return cap;
 }
 
diff --git a/src/drivers/usb/ehci.h b/src/drivers/usb/ehci.h
index e9437d40..d575727d 100644
--- a/src/drivers/usb/ehci.h
+++ b/src/drivers/usb/ehci.h
@@ -285,6 +285,12 @@ struct ehci_transfer_descriptor {
 /** SETUP token */
 #define EHCI_FL_PID_SETUP EHCI_FL_PID ( 2 )
 
+/** Error counter */
+#define EHCI_FL_CERR( count ) ( (count) << 2 )
+
+/** Error counter maximum value */
+#define EHCI_FL_CERR_MAX EHCI_FL_CERR ( 3 )
+
 /** Interrupt on completion */
 #define EHCI_FL_IOC 0x80
 
@@ -341,6 +347,34 @@ struct ehci_queue_head {
 /** Interrupt schedule mask */
 #define EHCI_CAP_INTR_SCHED( uframe ) ( 1 << ( (uframe) + 0 ) )
 
+/** Split completion schedule mask */
+#define EHCI_CAP_SPLIT_SCHED( uframe ) ( 1 << ( (uframe) + 8 ) )
+
+/** Default split completion schedule mask
+ *
+ * We schedule all split starts in microframe 0, on the assumption
+ * that we will never have to deal with more than sixteen actively
+ * interrupting devices via the same transaction translator.  We
+ * schedule split completions for all remaining microframes after
+ * microframe 1 (in which the low-speed or full-speed transaction is
+ * assumed to execute).  This is a very crude approximation designed
+ * to avoid the need for calculating exactly when low-speed and
+ * full-speed transactions will execute.  Since we only ever deal with
+ * interrupt endpoints (rather than isochronous endpoints), the volume
+ * of periodic traffic is extremely low, and this approximation should
+ * remain valid.
+ */
+#define EHCI_CAP_SPLIT_SCHED_DEFAULT					\
+	( EHCI_CAP_SPLIT_SCHED ( 2 ) | EHCI_CAP_SPLIT_SCHED ( 3 ) |	\
+	  EHCI_CAP_SPLIT_SCHED ( 4 ) | EHCI_CAP_SPLIT_SCHED ( 5 ) |	\
+	  EHCI_CAP_SPLIT_SCHED ( 6 ) | EHCI_CAP_SPLIT_SCHED ( 7 ) )
+
+/** Transaction translator hub address */
+#define EHCI_CAP_TT_HUB( address ) ( (address) << 16 )
+
+/** Transaction translator port number */
+#define EHCI_CAP_TT_PORT( port ) ( (port) << 23 )
+
 /** High-bandwidth pipe multiplier */
 #define EHCI_CAP_MULT( mult ) ( (mult) << 30 )