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

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Date:   Thu, 20 Feb 2020 19:21:18 +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 18:34, Rafael J. Wysocki <rafael@...nel.org> wrote:
> 
> 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.

Okay, thanks for the info.
I'll ask vendors the possibility to handle it at system firmware level.

Kai-Heng