linux-kernel - Re: [RFT][PATCH v2 1/2] PM / domains: Rework governor code to be more consistent

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Date:   Tue, 7 Nov 2017 00:07:04 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Tero Kristo <t-kristo@...com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Ramesh Thomas <ramesh.thomas@...el.com>,
        Alex Shi <alex.shi@...aro.org>
Subject: Re: [RFT][PATCH v2 1/2] PM / domains: Rework governor code to be more consistent

On Mon, Nov 6, 2017 at 3:38 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> [...]
>
>>>>
>>>> So I guess I'll simply evaluate dev_pm_qos_read_value(dev) if
>>>> subsys_data or subsys_data->domain_data is not there.
>>>
>>> Yes.
>>>
>>> However, if it returns -1, what value should you pick? 0?
>>
>> Without the second patch, -1 will just mean "no suspend", so the
>> parent cannot be suspended too, but that should just work AFAICS
>> (effective_constraint_ns may be -1 too at that point, if present).
>
> I am fine with whatever policy you pick.
>
> However, I suspect it may be more tricky respecting a -1 (no suspend),
> because this means dev_update_qos_constraint() then may continue to
> return a negative value, which you changed the caller,
> default_suspend_ok(), to not cope with.

Oh, I just need to restore the constraint_ns < 0 check I dropped,
because it was never going to trigger.

Thanks,
Rafael