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[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>
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mcb30 committed Mar 23, 2015
1 parent 5486c94 commit b418af2
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Showing 2 changed files with 53 additions and 11 deletions.
30 changes: 19 additions & 11 deletions src/drivers/usb/ehci.c
Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Expand All @@ -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;
Expand All @@ -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;
}

Expand Down
34 changes: 34 additions & 0 deletions src/drivers/usb/ehci.h
Expand Up @@ -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

Expand Down Expand Up @@ -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 )

Expand Down

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