Re: [PATCH RESEND] ahci: implement aggressive SATA device sleep support

On Wed, 2012-08-08 at 01:44 +0800, Shane Huang wrote:

Device Sleep is a feature as described in AHCI 1.3.1 Technical Proposal.
This feature enables an HBA and SATA storage device to enter the DevSleep
interface state, enabling lower power SATA-based systems.

Signed-off-by: Shane Huang <redacted> 

Am I missing the part where we actually send the command to the drive to
*enable* the DevSleep feature? And shouldn't we also read the MDAT/DETO
timings from the drive if it provides them (which it optionally can)?

Also, don't we need to revalidate the drive after a sleep/wake cycle?
How do we do that in the automatic/aggressive sleep case? After my
initial reading of the specs, I came to the conclusion that the *sleep*
is automatic, but the wakeup still requires careful handling (and we
need to ensure that we don't submit commands while it's asleep, etc.)?

Since the DevSleep line could just be a GPIO pin, I suspect we are going
to want to support platforms where it's not automatic, and we
assert/deassert it under direct software control. My test platform does
it with an ACPI call, in fact. Have you looked at that mode of operation
at all?

-- 
dwmw2