Question about SATA power management

[Edward Shao]

Hi~folks,

I'm interesting about power management for SATA but wondering about
AHCI ALPM, SATA HIPM and DIPM.

There are some questions would like to understand.

* ALPM is HIPM for AHCI?
* If ALPM is enabled but SATA HDD does not support HIPM (only DIPM),
ALPM is effective?
* hdparm -B is "Query/set Advanced Power Management feature".
This setting ("Advanced Power Management") is for DIPM?

Thanks you very much.

Best Regards,
Edward

[Nick Moszer]

Post by Edward Shao
Hi~folks,
I'm interesting about power management for SATA but wondering about
AHCI ALPM, SATA HIPM and DIPM.
There are some questions would like to understand.
* ALPM is HIPM for AHCI?

No, Advanced Link Power Management (ALPM) is a catch all for the three
link power management states on the SATA link.
These include Active, Partial and Slumber. Host Initiated Power
Mangement (HIPM) is the AHCI controller deciding and the drive agreeing
it's a good time to put the link into a PM state. The host initiates
the call to switch PM states. Device Initiated Power Management (DIPM)
is when the device decides and the host agrees that it's a good time to
put the link into a PM state.

Post by Edward Shao
* If ALPM is enabled but SATA HDD does not support HIPM (only DIPM),
ALPM is effective?

Personally I haven't seen a SATA HDD that supports DIPM but not HIPM.
If I recall correctly they all support HIPM but not all support DIPM.
If you were to find a drive that only supported DIPM

Post by Edward Shao
* hdparm -B is "Query/set Advanced Power Management feature".
This setting ("Advanced Power Management") is for DIPM?

You should look at the source for hdparm for the answer. Also take a
look at a tool we made here for working with AHCI and SATA Link PM

http://sourceforge.net/projects/ahcitool/

Post by Edward Shao
Thanks you very much.
Best Regards,
Edward
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