linux-kernel - Re: Hard Disk consumes lots of power in s2idle

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Message-ID: <CAJZ5v0in-v9iu88Wj0gAg_th-E-QWDSHZ_XvgyoOuqE=CZPtqQ@mail.gmail.com>
Date:   Thu, 20 Feb 2020 11:34:05 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        "open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)" 
        <linux-ide@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Kent Lin <kent.lin@...onical.com>, Tejun Heo <tj@...nel.org>
Subject: Re: Hard Disk consumes lots of power in s2idle

On Thu, Feb 20, 2020 at 11:25 AM Kai-Heng Feng
<kai.heng.feng@...onical.com> wrote:
>
>
>
> > On Feb 20, 2020, at 18:12, Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > On Thu, Feb 20, 2020 at 9:08 AM Kai-Heng Feng
> > <kai.heng.feng@...onical.com> wrote:
> >>
> >> Hi Srinivas,
> >>
> >>> On Feb 20, 2020, at 02:36, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> wrote:
> >>>
> >>> Hi Kai,
> >>>
> >>> On Wed, 2020-02-19 at 22:22 +0800, Kai-Heng Feng wrote:
> >>>> 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.
> >>
> >>>
> >>> 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.

OK

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

Well, if it were off, it would not draw power. :-)

So IMO it is reasonable to assume that the logic on the drive stays
on.  I'm not aware of anything that can be done to turn it off,
however.