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

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Message-Id: <CA007B3C-C084-429E-B774-70264A9E609F@canonical.com>
Date:   Thu, 20 Feb 2020 18:24:53 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     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 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.

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

Kai-Heng