Re: [RFC PATCH] ata: ahci: Enable DEVSLP by default on x86 modern standby platform

Hi Hans,


[...]

So digging a bit deeper I just realized that another important
difference
between med_power_with_dipm and min_power is that min_power by
default
set the ASP bits making the link go to the slumber state instead of
to
the partial (power-saving) state.

According to:
https://www.intel.com/content/dam/doc/reference-guide/sata-devices-im
plementation-recommendations.pdf

ASP defaults to off in the iRST drivers. But that is a document from
before DEVSLP got introduced.

So we need to know if Windows and/or the iRST drivers use HIPM and
ASP by default on these systems. If they do then using min_power
is fine. If they don't use one or the other we are going to need
a new policy reflecting those settings and use that.

Good point. In Windows there are various registry settings, so they can
be tuned. It is difficult to know what they mean.
Let me do some experiments to check impact of ASP on SLP_S0. Then I
will resubmit this patch.

Thanks,
Srinivas

Regards,

Hans