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Message-id: <5836A1E0.1070707@samsung.com>
Date: Thu, 24 Nov 2016 17:16:32 +0900
From: Chanwoo Choi <cw00.choi@samsung.com>
Organization: Samsung Electronics
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To: hl <hl@rock-chips.com>, myungjoo.ham@samsung.com
Cc: "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "dbasehore@chromium.org" <dbasehore@chromium.org>,
        "dianders@chromium.org" <dianders@chromium.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-rockchip@lists.infradead.org" 
        <linux-rockchip@lists.infradead.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Subject: Re: [PATCH v1 & v6 1/2] PM/devfreq: add suspend frequency support
References: <CGME20161124061416epcms1p44a0152bca14312f1229cab835ea0297f@epcms1p4>
 <20161124061416epcms1p44a0152bca14312f1229cab835ea0297f@epcms1p4>
 <58368C91.8030502@rock-chips.com> <5836927B.9010205@samsung.com>
 <5836980F.6050006@rock-chips.com>
In-reply-to: <5836980F.6050006@rock-chips.com>
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Hi Lin,

On 2016년 11월 24일 16:34, hl wrote:
> Hi Chanwoo Choi,
> 
>     I think the dev_pm_opp_get_suspend_opp() have implement most of
> the funtion, all we need is just define the node in dts, like following:
> 
> &dmc_opp_table {
>     opp06 {
>         opp-suspend;
>     };
> };

Two approaches use the 'opp-suspend' property.

I think that the method to support suspend-opp have to
guarantee following conditions:
- Support the all of devfreq's governors.
- Devfreq framework have the responsibility to change the
  frequency/voltage for suspend-opp. If we uses the
  new devfreq_suspend(), each devfreq device don't care
  how to support the suspend-opp. Just the developer of each
  devfreq device need to add 'opp-suspend' propet to OPP entry in DT file.

Best Regards,
Chanwoo Choi

> 
> so i think my way semm more simple.
> 
> On 2016年11月24日 15:10, Chanwoo Choi wrote:
>> + Tobias Jakobi,
>>
>> Hi Lin,
>>
>> We need to discuss how to support the suspend-opp of devfreq device.
>> Now, there are two patch thread for suspend-opp of devfreq.
>>
>> The Lin's approach modify the devfreq_suspend_device() to support suspend-opp.
>> The Tobias's approach[1] add new devfreq_suspend() and then call it on dpm_suspend()
>> when entering the suspend state.
>>
>> [1] [RFC 0/4] PM / devfreq: draft for OPP suspend impl
>> - https://patchwork.kernel.org/patch/9443323/
>> - https://patchwork.kernel.org/patch/9443325/
>> - https://patchwork.kernel.org/patch/9443329/
>> - https://patchwork.kernel.org/patch/9443331/
>>
>> I think we need to discuss it together.
>>
>> Regards,
>> Chanwoo Choi
>>
>> On 2016년 11월 24일 15:45, hl wrote:
>>> Hi MyungJoo Ham,
>>>
>>> On 2016年11月24日 14:14, MyungJoo Ham wrote:
>>>> On Thu, Nov 24, 2016 at 11:18 AM, hl <hl@rock-chips.com> wrote:
>>>>> Hi MyungJoo Ham,
>>>> []
>>>>>> We still need to sync the all status even i call target() in
>>>>>> devfreq_suspend/resume_device
>>>>>> directly, so still need update_devfreq() other setp except
>>>>>> devfreq->governor->get_target_freq(devfreq, &freq);
>>>>> And i think it better to be governor behaviors, for userspace they may not
>>>>> want to change
>>>>> the suspend frequency like other governor, the frequency should decide by
>>>>> the user, if they
>>>>> want this function, they should like other governor to rigister a
>>>>> devfreq_monitor_suspend().
>>>>> What do you think about my rev6 patch?
>>>> If I understand the intention correctly, this is for the stability of
>>>> the device due to the behavior or bootloader/SoC-initializer, which
>>>> has nothing to do with governors.
>>>>
>>>> Even if users are using userspace, as long as they set the custom
>>>> frequencies lower than the default, they have the possibility of
>>>> being unstable as ondemand is going to have.
>>>>
>>>>
>>>> To reuse the update_devfreq() code, you may do something like:
>>>>
>>>> static int _update_freq(struct devfreq *devfreq, bool is_suspending)
>>>> {
>>>>      /* original contents of update_freq with if statement with is_suspending wrapping get_target_freq */
>>>> }
>>>> int update_freq(struct devfreq *devfreq)
>>>> {
>>>>     return _update_freq(devfreq, false);
>>>> }
>>>>
>>>>
>>>> There should be other good non-invasive methods that are not governoe-specific as well.
>>>>
>>> Thanks for your suggestion, i will update the new version soon.
>>>> Cheers,
>>>> MyungJoo
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Linux-rockchip mailing list
>>>> Linux-rockchip@lists.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/linux-rockchip
>>> -- 
>>> Lin Huang
>>>
>>
>>
>>
>