UNH InterOperability Lab

January 9, 2018 | Author: Anonymous | Category: Engineering & Technology, Electrical Engineering
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UNH InterOperability Lab Serial ATA (SATA) Clause 8: OOB and Phy Power States

Improving Networks Worldwide.

SATA Clause 8

Presentation Topics • Interface Power States • Asynchronous Signal Recovery • OOB and Signature FIS return • Power-On Sequence State Machine

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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)

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SATA Clause 8

Interface Power States

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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

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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) 6

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

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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

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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

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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 10

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 11

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

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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 13

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 14

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

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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 16

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

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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

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OOB and Signature FIS return • Possible Solution:

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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

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SATA Clause 8

Power-On Sequence State Machine • In states where: – the Phy relies on detection of received ALIGNp primitives OR – comma sequences for state transitions

• Phy shall: – ensure accurate detection of received ALIGNp primitives at the compatible signaling rate (continued on next slide)

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SATA Clause 8

Power-On Sequence State Machine • Phy shall: – Have adequate implementation safeguards to ensure no misdetection of ALIGNp

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