Improving Networks Worldwide. UNH InterOperability Lab Serial ATA (SATA) Clause 8: OOB and Phy Power States

2 SATA Clause 8 Presentation Topics Interface Power States Asynchronous Signal Recovery OOB and Signature FIS return Power-On Sequence State Machine

3 SATA Clause 8 Interface Power States Serial ATA interface power states are controlled by: –The device –The host controller There are three Interface Power States (see table on next slide)

4 SATA Clause 8 Interface Power States

5 SATA Clause 8 Asynchronous Signal Recovery Is optional Phys may support ASR for applications where the usage model of device insertion into a receptacle (power applied at the time of insertion) does not apply

6 SATA Clause 8 Asynchronous Signal Recovery What happens: –When a signal is lost, both the host and device can attempt to recover it –Loss of signal can be determined by the host or device. –Loss of signal is represented as a transition from PHYRDY to PHYRDYn (associated with entry into states LS1: NoCommErr or LS2: NoComm within Link Layer)

7 SATA Clause 8 Asynchronous Signal Recovery What happens (continued) –Note: negation of PHYRDY does not always mean a loss of signal –Recovery of signal is associated with exit from state LS2: NoComm –Either the device or host will attempt to recover the signal

8 SATA Clause 8 Asynchronous Signal Recovery Device: –If the device attempts to recover the signal before the host, it will issue a COMINIT –The device will return its signature following completion of the OOB sequence which included COMINIT

9 SATA Clause 8 Asynchronous Signal Recovery Host: –If a host supports ASR, upon receiving an unsolicited COMINIT from the device, it will issue a COMRESET (to the device) Note: –Unsolicited COMINIT: A COMINIT that was not in response to a preceding (immediately before) COMRESET

10 SATA Clause 8 Asynchronous Signal Recovery Host: –When COMRESET is sent to the device in response to an unsolicited COMINIT: Host shall set Status register to 7Fh Host shall set all other Shadow Command Block Registers to FFh –When COMINIT is received in response to COMRESET (associated with entry into state HP2B:HR_AwaitNoCOMINIT) Shadow Status register value shall be set to FFh or 80h to reflect that a device is attached

11 SATA Clause 8 Unsolicited COMINT usage Informative Issuing COMRESET to a device causes it to lose software settings –If software settings preservation is supported (SSP), this will not happen If COMRESET was due to ASR and legacy mode software is in use –Software does not replace lost software settings

12 SATA Clause 8 Unsolicited COMINT usage Note: –Issuing a non-commanded COMRESET to the device should be minimized –Want to ensure correct operation with legacy mode software –Avoid inadvertent loss of critical software settings

13 SATA Clause 8 Unsolicited COMINT usage Original use was only for when the signal is lost between the host and device Host (based on Host Phy Initialization Stat Machine) shall assume when receiving an unsolicited COMINIT: –A new device was connected OR –The cable was unplugged and communication was lost to the device

14 SATA Clause 8 Unsolicited COMINT usage Proper Host response to an unsolicited COMINIT is to issue a COMRESET –This will put the device into a known state When device issues an unsolicited COMINIT and the host responds with COMRESET, the software settings of the device could be changed –Legacy mode software might not recover

15 SATA Clause 8 Unsolicited COMINT usage The device should only issue an unsolicited COMINIT when: –Phy voltage threshold falls below the minimum value OR –Last resort in error recovery This will minimize potential exposure to software loss issues

16 SATA Clause 8 OOB and Signature FIS return Informative What happens: –After an OOB sequence –Only if the device recognized COMRESET during the OOB –Happens with devices compliant to older revisions of SATA specification –Result: devices may send a Register – Device to Host FIS with the device signature

17 SATA Clause 8 OOB and Signature FIS return Solution: –For compatibility with older devices –Host may ensure a system power-on event Device always receives a valid COMRESET after power is determined good at the device –Note: hot plug aware software will ensure device always receives a COMRESET on a hot plug event

18 SATA Clause 8 OOB and Signature FIS return One specific solution: –Host workaround –Perform following software procedure when determining device presence (on next slide) –Note: other methods for ensuring the device receives a COMRESET in these conditions are possible

19 SATA Clause 8 OOB and Signature FIS return Possible Solution:

20 SATA Clause 8 Power-On Sequence State Machine Consist of State Diagrams Specify expected behavior of the host and device Phy from power-on to establishment of an active communication channel

21 SATA Clause 8 Power-On Sequence State Machine In states where: – the Phy relies on detection of received ALIGN p primitives OR –comma sequences for state transitions Phy shall: – ensure accurate detection of received ALIGN p primitives at the compatible signaling rate (continued on next slide)

22 SATA Clause 8 Power-On Sequence State Machine Phy shall: –Have adequate implementation safeguards to ensure no misdetection of ALIGN p