With an USB3 device using the cypress FX3 we face the situation where the devices RTS state machine gets out of sync with the hosts state machine during restart of the system: While the device goes from 'U1' to 'U2' state the host changes into 'Polling.LFPS' state (see attached USB trace). As consequence the device is not operational.
As Host platform we use a PC with Intel i7-6700 with xHCI root hub running Win 10; The USB LPM power option is set to 'Moderat power settings'.
Observations:
To eliminate the problem we can change the LPM power options in Windows to "Off" - as this is a modification on host side this is not a preferred solution.
Also preventing the transition from 'U1' to 'U2' state (by returning CyFalse in LPMRequestCallback when 'U2' is requested) eliminates the problem - but then complience to USB Chapter 9 is lost.
Question:
How can we get our device operate reliably with the host when the LPM power options is set to 'Moderat power settings' which is the default configuration in Win 10?
Roland,
I can not comment on why the host is entering into LFPS.Polling instead of sending LFPS Exit. Please check with host controller vendor.
Here is the Exit from U2 requirements from the USB 3.0 Spec.
Section 7.5.8.2 Exit from U2
• A downstream port shall transition to eSS.Disabled when directed.
• A downstream port shall transition to Rx.Detect upon detection of a far-end high-impedance
receiver termination (ZRX-HIGH-IMP-DC-POS) defined in Table 6-21.
• A downstream port shall transition to Rx.Detect when directed to issue Warm Reset.
• An upstream port shall transition to Rx.Detect when Warm Reset is detected.
• A self-powered upstream port shall transition to eSS.Disabled upon not detecting valid Vbus as
defined in Section 11.4.5.
• The port shall transition to Recovery upon successful completion of a LFPS handshake meeting
the U2 LFPS exit signaling defined in Section 6.9.2.
• The port shall transition to eSS.Inactive upon the 2-ms LFPS handshake timer timeout
(tNoLFPSResponseTimeout) and a successful LFPS handshake meeting the U2 LFPS exit
handshake signaling in Section 6.9.2 is not achieved.
