linux-kernel - Re: [PATCH 2/2] thermal: rcar_thermal: use pm_runtime_put

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Message-ID: <CAMuHMdWSMsVZYF2jswCoRB217n_3OR8uikNtBYOfQHkQs3oWSA@mail.gmail.com>
Date:	Tue, 10 Nov 2015 09:18:35 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Zhang Rui <rui.zhang@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Linux-SH <linux-sh@...r.kernel.org>,
	Linux-Kernel <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Cao Minh Hiep <cm-hiep@...so.co.jp>,
	Dung：人ソ <nv-dung@...so.co.jp>
Subject: Re: [PATCH 2/2] thermal: rcar_thermal: use pm_runtime_put_sync()

Hi Morimoto-san, Ulf,

On Tue, Nov 10, 2015 at 3:12 AM, Kuninori Morimoto
<kuninori.morimoto.gx@...esas.com> wrote:
> From: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
>
> It is using pm_runtime_get_sync() on probe(). Let's use
> pm_runtime_put_sync() instead of pm_runtime_put(). Otherwise thermal
> sensor doesn't work after unbind/re-bind
>
> Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
> ---
>  drivers/thermal/rcar_thermal.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/rcar_thermal.c b/drivers/thermal/rcar_thermal.c
> index 13d01ed..f7cf2d7 100644
> --- a/drivers/thermal/rcar_thermal.c
> +++ b/drivers/thermal/rcar_thermal.c
> @@ -373,7 +373,7 @@ static int rcar_thermal_remove(struct platform_device *pdev)
>                 thermal_zone_device_unregister(priv->zone);
>         }
>
> -       pm_runtime_put(dev);
> +       pm_runtime_put_sync(dev);
>         pm_runtime_disable(dev);
>
>         return 0;

While I can confirm this fixes the issue, I think this is a bug in the PM
core, and thus your patch is merely a workaround.

Morimoto-san: I assume this is a recent regression. Have you tried to bisect?

With a bit more debugging info, this is the difference between the failing
and the "fixed" cases:

 unbind:

+rcar_thermal e61f0000.thermal: pm_clk_suspend()
+renesas-cpg-mssr e6150000.clock-controller: MSTP 522/thermal OFF
 rcar_thermal e61f0000.thermal: removing from PM domain clock-controller
 pm_genpd_remove_device: Remove e61f0000.thermal from clock-controller
-renesas-cpg-mssr e6150000.clock-controller: MSTP 522/thermal OFF

 bind:

 rcar_thermal e61f0000.thermal: adding to PM domain clock-controller
 __pm_genpd_add_device: Add e61f0000.thermal to clock-controller
 rcar_thermal e61f0000.thermal: Clock thermal con_id (null) managed by
runtime PM.
-rcar_thermal e61f0000.thermal: thermal sensor was broken
+rcar_thermal e61f0000.thermal: pm_clk_resume()
+renesas-cpg-mssr e6150000.clock-controller: MSTP 522/thermal ON
 rcar_thermal e61f0000.thermal: 1 sensor probed

In the failing case, pm_clk_suspend() is not called, and turning off the
module clock is thus delayed until removal of the device from the clock
domain.
But as pm_clk_suspend() wasn't called, the device isn't correctly resumed on
rebind, and the module clock is never re-enabled, leading to a failure.

Ulf, what do you think?

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
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