linux-kernel - Re: [PATCH v2] PM / Domains: Keep the pd status during system PM phases

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Date:   Tue, 07 Feb 2017 17:22:51 +0800
From:   Elaine Zhang <zhangqing@...k-chips.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
CC:     Feng Xiao <xf@...k-chips.com>, Heiko Stuebner <heiko@...ech.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>, Pavel Machek <pavel@....cz>,
        Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Tao Huang <huangtao@...k-chips.com>, xxx@...k-chips.com,
        Caesar Wang <wxt@...k-chips.com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] PM / Domains: Keep the pd status during system PM
 phases



On 02/07/2017 04:19 PM, Ulf Hansson wrote:
> [...]
>
>>>
>>>
>>> Unfortunate, I am still not fully understanding the scenarios. As you
>>> indicate, the problem seems related to wakeup settings.
>>>
>>> Could you please try to answer the below questions, hopefully it helps
>>> me to better understand.
>>>
>>> 1)
>>> While starting the system suspend sequence, under what circumstances
>>> are you expecting the vdd_gpu and pd_gpu to be powered on?
>>>
>>
>> I don't want to power on the vdd_gpu and pd_gpu during the system suspend
>> sequence.
>> I hope the pd_gpu and vdd_gpu power on/off just by gpu device.
>
> Let me rephrase my question.
>
> Can the vdd_gpu/pd_gpu ever remain in a powered on state while the
> system is suspended?
>
NO, the vdd_gpu/pd_gpu ever remain in a powered off state while the
system is suspended.
> If yes, when is that the case?
>
>>
>>> 2)
>>> While starting the system suspend sequence, under what circumstances
>>> are you expecting the vdd_gpu and the pd_gpu to be powered off?
>>>
>>
>> I don't want to power off the vdd_gpu and pd_gpu during the system suspend
>> sequence.
>> Because before the system suspend,the vdd_gpu and pd_gpu has been power off
>> by gpu device(pm_ruantime_put).
>
> *Exactly*, how do you guarantee that a pm_runtime_put() for the gpu
> device triggers a runtime suspend - before a system suspend sequence
> starts?
>
> For example, userspace may via sysfs prevent runtime suspend for any
> device with runtime PM enabled.
>
Yes, you are right.I did't consider this.
Whether on or off pd_gpu, the vdd_gpu is must be enabled.How to deal 
with the enable/disable the vdd_gpu?

our process in devices/platform/ff9a0000.gpu:
device init
	pm_runtime_enable()

gpu_power_on
	regulator_enable(vdd_gpu)
	pm_runtime_get_sync(pd_gpu)

gpu_power_off
	pm_runtime_put_sync(pd_gpu)
	regulator_disable(vdd_gpu)

device remove
	pm_runtime_disable()

>>
>>> 3)
>>> What devices are attached to vdd_gpu?
>>>
>> just pd_gpu
>>>
>>> 4)
>>> What devices are attached to pd_gpu?
>>>
>> just gpu device(mali driver)
>>
>> vdd_gpu
>> ------- pd_gpu
>> ----------------devices/platform/ff9a0000.gpu
>>>
>>>
>
> Thanks for these details, very useful!
>
> [...]
>
> Kind regards
> Uffe
>
>
>