On Feb 20, 2020, at 18:12, Rafael J. Wysocki [off-list ref] wrote:

On Thu, Feb 20, 2020 at 9:08 AM Kai-Heng Feng
[off-list ref] wrote:

quoted

Hi Srinivas,

quoted

On Feb 20, 2020, at 02:36, Srinivas Pandruvada [off-list ref] wrote:

Hi Kai,

On Wed, 2020-02-19 at 22:22 +0800, Kai-Heng Feng wrote:

quoted

Hi Srinivas,

Your previous work to support DEVSLP works well on SATA SSDs, so I am
asking you the issue I am facing:
Once a laptop has a HDD installed, the power consumption during
S2Idle increases ~0.4W, which is quite a lot.
However, HDDs don't seem to support DEVSLP, so I wonder if you know
to do proper power management for HDDs?

What is the default here
cat /sys/power/mem_sleep
s2idle or deep?

It defaults to s2idle.

quoted

Please follow debug steps here:
https://01.org/blogs/qwang59/2018/how-achieve-s0ix-states-linux

We need to check whether you get any PC10 residency or not.

Yes it reaches PC10. It doesn't reach SLP_S0 though.
The real number on S2Idle power consumption:
No HDD: ~1.4W
One HDD: ~1.8W

If the SoC doesn't hit PC10 the number should be significantly higher.
That's why I think the issue is the power management on HDD itself.

I'm assuming that you mean a non-SSD device here.

Yes, it's spinning rust here.

That would be handled via ata_port_suspend() I gather and whatever
that does should do the right thing.

Do you think that the disk doesn't spin down or it spins down, but the
logic stays on?

The spin sound is audible, so I am certain the HDD spins down during S2Idle.

How do I know if the logic is on or off?

Kai-Heng