Hello, I've been testing the Linux based SATA link pm capabilities of drives for a project. I have come across a curious set of drives and wonder if anyone on the list can shed light on the issues. Some drives appear never to go to partial on the link when "medium_power" is written to link_power_management_policy at /sys/class/scsi_host/hostX.. All drives I've tested will go to slumber when "min_power" is written. The drives that do go to partial when set through sysfs also allow manual transitions, a.k.a writing to the AHCI port command register directly to force it to a pm mode. The drives that do not go to partial when set through sysfs will NOT allow any manual transitions. I don't have a SATA bus sniffer handy so I can't see the primitives to find out exactly what is going on. The drives I've found that won't go to partial when enabled through sysfs are: Seagate Momentus ST9160821AS Seagate Momentus ST9160823AS Lite-On DVDRW/CDRW DS-8A2S I saw the note about DIPM in libata-core.c ata_dev_set_dipm() and partial. This does not appear to be the case as everything I'm talking about is HIPM. I'm wondering if perhaps some drives just don't support partial on the link? Using hdparm -I on the Seagate drives the output w/ regards to PM is the same "Advanced Power Management" is supported on both drives that work and don't work. Does anyone know of a way to tell if these drives actually support partial and the driver needs work or if these drives just plain don't support it? I haven't come across anything in the AHCI or SATA specs that say if it's optional. They make it seem like both partial and slumber are mandatory. Thanks! Nick Moszer _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
