linux-kernel - Re: [PATCH 0/2] PM / core: genpd fix and pm_runtime_force

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Message-ID: <CAMuHMdWLkji-GwtFW=RTW12bg_k01DgFocALt6fFF3bGAy6HAg@mail.gmail.com>
Date:   Mon, 15 Jan 2018 14:22:08 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH 0/2] PM / core: genpd fix and pm_runtime_force_suspend|resume()
 rework

Hi Rafael,

On Mon, Jan 15, 2018 at 9:16 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> On Mon, Jan 15, 2018 at 1:04 AM, Rafael J. Wysocki <rafael@...nel.org> wrote:
>> On Sun, Jan 14, 2018 at 10:48 AM, Geert Uytterhoeven
>> <geert@...ux-m68k.org> wrote:
>>> On Sat, Jan 13, 2018 at 1:38 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>>>> On Friday, January 12, 2018 3:31:09 PM CET Geert Uytterhoeven wrote:
>>>>> On Fri, Jan 12, 2018 at 2:00 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>>>>> > This comes from the recent discussion/testing effort that ensued after my
>>>>> > pm_runtime_force_suspend|resume() changes proposal:
>>>>> >
>>>>> > https://marc.info/?t=151497772000004&r=1&w=2
>>>>> >
>>>>> > Patch [1/2] basically is https://patchwork.kernel.org/patch/10152873/ rebased
>>>>> > on top of the current linux-next branch of the linux-pm.git tree (the relevant
>>>>> > part should be there in the linux-next tree proper ATM).  It applies on top
>>>>> > of https://patchwork.kernel.org/patch/10156077/ which should apply to the Linus'
>>>>> > tree cleanly.
>>>>> >
>>>>> > Patch [2/2] is a resend of https://patchwork.kernel.org/patch/10142047/ with
>>>>> > a very minor changelog modification and the R-b tag from Ulf.
>>>>> >
>>>>> > Geert, if possible, please test this on the Renesas systems that had the
>>>>> > problem with https://patchwork.kernel.org/patch/10142047/ previously and let
>>>>> > me know if you still see issues.
>>>>>
>>>>> I've tested this on two very similar systems: Salvator-XS with R-Car H3 ES2.0,
>>>>> and Salvator-X with R-Car M3-W ES1.0.
>>>>>
>>>>> On the M3-based system, everything seems to work fine.
>>>>
>>>> Good.
>>>>
>>>>> On the H3-based system, the serial console (the /dev/ttySC0 device, not kernel
>>>>> serial output) is dead after resume from s2ram, with and without
>>>>> no_console_suspend.
>>>>>
>>>>> With no_console_suspend, I see:
>>>>>
>>>>>     ttySC ttySC0: 1 input overrun(s)
>>>>>
>>>>> after typing on the serial console, so it looks like an interrupt problem.
>>>>>
>>>>> This issue seems to be caused by patch [1/2]. But I have no idea what's
>>>>> really happening, and why the two systems behave differently.
>>>
>>> Could be a firmware issue, too.
>>> While the kernel images are identical, the ARM trusted firmware configs aren't
>>> (same version, though).
>>>
>>> I'll do some more investigation...
>>
>> OK, thanks!
>>
>> It also would be good to know the topology of the device hierarchy and
>> how that maps to the domains on the failing system (and which UART
>> clocks are operated by genpd).
>
> The topology is the same on both systems.

I did miss a small difference in topology: in pm/linux-next, H3 has DMA
enabled for SCIF2, while M3 hasn't (yet).
With DMA enabled on M3, it fails in the same way.

As genpd_resume_noirq() no longer calls pm_runtime_force_resume(),
rcar_dmac_runtime_resume() is no longer called, and the DMAC's registers
are no longer reinitialized after system resume, breaking the serial port.

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