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

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Message-ID: <CAMuHMdX4WjXZQrP9QMGFV8sbntOUvfZ4y-uQSS4_4ArrCjsxWA@mail.gmail.com>
Date:   Tue, 31 Oct 2017 14:55:02 +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>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        DRI Development <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] PM / QoS: Fix default runtime_pm device resume latency

Hi Rafael, Tero,

CC pinchartl, dri-devel

On Tue, Oct 31, 2017 at 2:10 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> CC linux-renesas-soc
>
> On Tue, Oct 31, 2017 at 2:09 PM, Geert Uytterhoeven
> <geert@...ux-m68k.org> wrote:
>> 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

 3. I've just bisected a seemingly unrelated issue to the same commit.
    On Salvator-XS with R-Car H3, initialization of the rcar-du driver now
    takes more than 1 minute due to flip_done time outs, while it took 0.12s
    before:

    [    3.015035] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
    [    3.021721] [drm] No driver support for vblank timestamp query.
    [   13.280738] [drm:drm_atomic_helper_wait_for_flip_done] *ERROR*
[CRTC:58:crtc-3] flip_done timed out
    [   23.520707] [drm:drm_atomic_helper_commit_cleanup_done] *ERROR*
[CRTC:58:crtc-3] flip_done timed out
    [   33.760708] [drm:drm_atomic_helper_wait_for_flip_done] *ERROR*
[CRTC:58:crtc-3] flip_done timed out
    [   44.000755] [drm:drm_atomic_helper_commit_cleanup_done] *ERROR*
[CRTC:58:crtc-3] flip_done timed out
    [   44.003597] Console: switching to colour frame buffer device 128x48
    [   54.240707] [drm:drm_atomic_helper_wait_for_flip_done] *ERROR*
[CRTC:58:crtc-3] flip_done timed out
    [   64.480706] [drm:drm_atomic_helper_commit_cleanup_done] *ERROR*
[CRTC:58:crtc-3] flip_done timed out
    [   64.544876] rcar-du feb00000.display: fb0:  frame buffer device
    [   64.552013] [drm] Initialized rcar-du 1.0.0 20130110 for
feb00000.display on minor 0
    [   64.559873] [drm] Device feb00000.display probed

>> Commit 2a9a86d5c81389cd ("PM / QoS: Fix default runtime_pm device resume
>> latency") fixes the second issue, but not the first.

... nor the third.

>> Reverting commits 2a9a86d5c81389cd ("PM / QoS: Fix default runtime_pm
>> device resume latency") and 0cc2b4e5a020fc7f ("PM / QoS: Fix device resume
>> latency PM QoS") fixes both.

... all three.

>> Do you have a clue?
>> Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds