linux-kernel - Re: [PATCH] PM / QoS: Fix default runtime

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Message-ID: <CAMuHMdW3AJFZQVDPTcpL-UMRxNThcOpQxNz6yTx9qDP7SQ-kLg@mail.gmail.com>
Date:   Tue, 31 Oct 2017 14:10:46 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Tero Kristo <t-kristo@...com>, Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH] PM / QoS: Fix default runtime_pm device resume latency

CC linux-renesas-soc

On Tue, Oct 31, 2017 at 2:09 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> Hi Rafael, Tero,
>
> On Tue, Oct 31, 2017 at 12:27 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> On Monday, October 30, 2017 11:19:08 AM CET Rafael J. Wysocki wrote:
>>> On Mon, Oct 30, 2017 at 8:10 AM, Tero Kristo <t-kristo@...com> wrote:
>>> > The recent change to the PM QoS framework to introduce a proper
>>> > no constraint value overlooked to handle the devices which don't
>>> > implement PM QoS OPS. Runtime PM is one of the more severely
>>> > impacted subsystems, failing every attempt to runtime suspend
>>> > a device. This leads into some nasty second level issues like
>>> > probe failures and increased power consumption among other things.
>>>
>>> Oh, that's bad.
>>>
>>> Sorry about breaking it and thanks for the fix!
>>>
>>> > Fix this by adding a proper return value for devices that don't
>>> > implement PM QoS implicitly.
>>> >
>>> > Fixes: 0cc2b4e5a020 ("PM / QoS: Fix device resume latency PM QoS")
>>> > Signed-off-by: Tero Kristo <t-kristo@...com>
>>> > Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>
>>> Applied.
>>
>> And pushed to Linus.
>
> I'm afraid it is not sufficient.
>
> Commit 0cc2b4e5a020fc7f ("PM / QoS: Fix device resume latency PM QoS")
> introduced two issues on Renesas platforms:
>  1. After boot up, many devices have changed their state from "suspended"
>     to "active", according to /sys/kernel/debug/pm_genpd/pm_genpd_summary
>     (comparing that file across boots is one of my standard tests).
>     Interestingly, doing a system suspend/resume cycle restores their state
>     to "suspended".
>
>  2. During system suspend, the following warning is printed on
>     r8a7791/koelsch:
>
>         i2c-rcar e6530000.i2c: runtime PM trying to suspend device but
> active child
>
> Commit 2a9a86d5c81389cd ("PM / QoS: Fix default runtime_pm device resume
> latency") fixes the second issue, but not the first.
>
> Reverting commits 2a9a86d5c81389cd ("PM / QoS: Fix default runtime_pm
> device resume latency") and 0cc2b4e5a020fc7f ("PM / QoS: Fix device resume
> latency PM QoS") fixes both.
>
> Do you have a clue?
> Thanks!