ATA Power Management SATA Device Initiated Power Management (DIPM)

Transcription

1 ATA/ATAPI T13 / e04149-r0 ATA Power Management SATA Device Initiated Power Management (DIPM) John Masiewicz Western Digital john.masiewicz@wdc.com John Masiewicz October 8, 2004

2 Background SATA Interface Power Management Applies to SATA Phy block only Independent of drive power management Can be tied to drive PM: Standby, Sleep, Idle SATA interface PM has three states ACTIVE: Phy ready, full power, TX/RX on PARTIAL: reduced power, resumes in under 10 us SLUMBER: reduced power, resumes in under 10 ms 2

3 Background Active PARTIAL X SLUMBER Entering PARTIAL or SLUMBER Host or device may send PMREQ_P or PMREQ_S To resume from PARTIAL or SLUMBER, either host or device Sends COMWAKE OOB, Receives COMWAKE response, and moves to Phy ready. Resumes right where it left off Main question is WHEN should a Device initiate SATA PM? 3

4 Implementation IDENTIFY DEVICE Word 76, Bit 9 If 1, Device supports receipt of host initiated interface PM Word 78, Bit 3 If 1, Device supports initiating interface PM Word 79, Bit 3 If 1, Device initiating interface PM is enabled. SET FEATURES command to enable/disable 4

5 Host Initiated Power Management Host Initiated Interface PM (HIPM) Device should be able to respond to PMREQ_P, PMREQ_S & COMWAKE, and change Phy Power Management state. Device should not NAK PM requests from host. If host issues PMREQ while commands are queued, it is better to enter PM and then issue COMWAKE to host when a released command is ready for data transfer. Exception, data is ready to transfer when PMREQ received, and device sends X_RDY (not NAK). Very simple if no commands are outstanding. Device will not exit PM, wait for Host COMWAKE 5

6 Device Initiated Power Management Device Initiated Interface PM (DIPM) If enabled, Device is manages SATA Interface power Based on Command Status and Partial/Slumber timers Programmable timers allow for more / less aggressive models. Implement two timers: Partial Timer (Typically 1-5 ms?) Slumber Timer (Typically ms?) HW or FW timers, and same timer feature can be used for both. May be host programmable, (SET FEATURES or VSC commands?) An implementation algorithm is proposed here that implements DIPM without new commands or Serial Transport Features. 6

7 Device Initiated Interface PM Recommended DIPM Algorithm Following assumptions are made Device must support SATA PM protocol. (PMREQ_P, PMREQ_S) Timer (HW/FW) be used for Partial/Slumber timers. COMWAKE or Phy Ready interrupt to inform link of Resume. COMRESET detection still functional while in PM modes Some start / Stop Device Initiated PM timer/function Algorithm based 7

8 Device Initiated Interface PM Recommended DIPM Algorithm, continue PARTIAL timer: Clear/Stop Partial timer when a transfer starts, TX or RX. Load/Start Partial timer when a transfer is complete, TX or RX. When timer expires Initiate PARTIAL state. If PARTIAL successful, Load/Start SLUMBER timer. SLUMBER timer: When timer expires Transmit COMWAKE to go to ACTIVE. Initiate PMREQ_S to go to SLUMBER state. If host NAK s Slumber, restart PARTIAL timer. 8

9 Device Initiated Interface PM POWER UP Host or Device COMWAKE SLUMBER STATE Host PMACK Drive PM Sleep, Standby, Idle Host or Device COMWAKE ACTIVE1 Load/Start PARTIAL Timer Host PMNAK PARTIAL timer Expired X_RDY ACTIVE3 Device Init PARTIAL Send PMREQ_P Host PMACK PARTIAL1 Load/Start SLUMBER Timer SLUMBER timer Expired PARTIAL2 Device Init ACTIVE State Device COMWAKE ACTIVE4 Device Init SLUMBER Send PMREQ_S Command Received No Commands Pending If PARTIAL Disabled Rx, Tx Start or Host PMNAK ACTIVE2 Stop PARTIAL Timer Device Initiated SATA power management state machine 9

10 Device Initiated Interface PM Recommended DIPM, Advantages Easy to implement Vendor Independent No new commands or Serial Transport functions Actions that may start Device Initiated Interface PM Any SATA specific Phy PM (Shown in state machine) PATA PM Commands (Shown in state machine) Vendor specific drive PM modes ATA Advance Power Management timer (??) Of course host can initiate PM state change anytime Includes PM retry with timers Easily expanded for future mobile enhancements Inter and Intra-command DIPM 10