Port Routing Control Via Portowner And Disconnect Event - Intel IXP45X Developer's Manual

USB 2.0 Host Controller—Intel
9.14.2.2

Port Routing Control via PortOwner and Disconnect Event

Manipulating the port routing via the CF-bit is an extreme process and not intended to
be used during normal operation. The normal mode of port ownership transferal is on
the granularity of individual ports using the Port Owner bit in the EHCI HC's PORTSC
register (for hand-offs from EHCI to companion host controllers). Individual port
ownership is returned to the EHCI controller when the port registers a device
disconnect. When the disconnect is detected, the port routing logic immediately returns
the port ownership to the EHCI controller. The companion host controller port register
detects the device disconnect and operates normally.
Under normal operating conditions (assuming all HC drivers loaded and operational and
the EHCI CF-bit is set to a one), the typical port enumeration sequence proceeds as
illustrated below:
• Initial condition is that EHCI is port owner. A device is connected causing the port to
detect a connect, set the port connect change bit and issue a port-change interrupt
(if enabled).
• EHCI Driver identifies the port with the new connect change bit asserted and sends
a change report to the hub driver. Hub driver issues a GetPortStatus() request and
identifies the connect change. It then issues a request to clear the connect change,
followed by a request to reset and enable the port.
• When the EHCI Driver receives the request to reset and enable the port, it first
checks the value reported by the LineStatus bits in the PORTSC register. If they
indicate the attached device is a full-speed device (e.g. D+ is asserted), then the
EHCI Driver sets the PortReset control bit to a one (and sets the PortEnable bit to a
zero) which begins the reset-process. Software times the duration of the reset,
then terminates reset signaling by writing a zero to the port reset bit. The reset
process is actually complete when software reads a zero in the PortReset bit. The
EHCI Driver checks the PortEnable bit in the PORTSC register. If set to a one, the
connected device is a high-speed device and EHCI Driver (root hub emulator)
issues a change report to the hub driver and the hub driver continues to enumerate
the attached device.
• At the time the EHCI Driver receives the port reset and enable request the
LineStatus bits might indicate a low-speed device. Additionally, when the port reset
process is complete, the PortEnable field may indicate that a full-speed device is
attached. In either case the EHCI driver sets the PortOwner bit in the PORTSC
register to a one to release port ownership to a companion host controller.
• When the EHCI Driver sets PortOwner bit to a one, the port routing logic makes the
connection state of the transceiver available to the companion host controller port
register and removes the connection state from the EHCI HC port. The EHCI
PORTSC register observes and reports a disconnect event via the disconnect
change bit. The EHCI Driver detects the connection status change (either by polling
or by port change interrupt) and then sends a change report to the hub driver.
When the hub driver requests that port-state, the EHCI Driver responds with a
reset complete change set to a one, a connect change set to a one and a connect
status set to a zero. This information is derived directly from the EHCI port register.
This will allow the hub driver to assume the device was disconnected during reset.
It will acknowledge the change bits and wait for the next change event. While the
EHCI controller does not own the port, it simply remains in a state where the port
reports no device connected.
The device-connect evaluation circuitry of the companion HC activates and detects
the device, the companion Driver detects the connection and enumerates the port.
When a port is routed to a companion HC, it remains under the control of the
companion HC until the device is disconnected from the root port (ignoring for now the
scenario where EHCI's CF-bit transitions from a 1b to a 0b). When a disconnect occurs,
the disconnect event is detected by both the companion HC port control and the EHCI
port ownership control. On the event, the port ownership is returned immediately to
August 2006
Order Number: 306262--, Revision: 004US
® ®
IXP45X and Intel IXP46X Product Line of Network Processors
Intel
® ®
IXP45X and Intel IXP46X Product Line of Network Processors
Developer's Manual
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