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

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Date:   Tue, 7 Feb 2017 09:19:09 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Elaine Zhang <zhangqing@...k-chips.com>
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

[...]

>>
>>
>> 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?

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.

>
>> 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