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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 16 Oct 2020 08:44:05 +0200
Message-ID: <CAMuHMdUUzoFxbJts3gVC7i5A5daa_TYzKdrGEHho=3a1eeC_ww@mail.gmail.com>
Subject: Re: [PATCH V2 2/2] cpufreq: dt: Refactor initialization to handle
 probe deferral properly
To:     Viresh Kumar <viresh.kumar@linaro.org>
Cc:     Stephan Gerhold <stephan@gerhold.net>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Stephen Boyd <sboyd@kernel.org>, Nishanth Menon <nm@ti.com>,
        nks@flawful.org, Georgi Djakov <georgi.djakov@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Wolfram Sang <wsa@the-dreams.de>,
        Linux I2C <linux-i2c@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Viresh,

On Fri, Oct 16, 2020 at 7:03 AM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> On 14-10-20, 18:40, Geert Uytterhoeven wrote:
> > On this platform (r8a7791-koelsch.dts), there is no opp table in DT.

I think you missed the clue above: this DTS does not have an opp-table
with operating-points-v2, but cpu0 does have the operating-points (v1)
property (note the latter is something I missed before).

> >
> >   Before:
>
> I assume this means before this patchset came in..

Indeed.

> >     boot:
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:362
> >       cpu cpu0: resources_available:95
> >       cpu cpu0: resources_available:102: clk_get() returned z
> >       cpu cpu0: resources_available:120:
> > dev_pm_opp_of_find_icc_paths() returned 0
> >       cpu cpu0: resources_available:125: find_supply_name() returned cpu0
> >       cpu cpu0: resources_available:132: regulator_get_optional()
> > returned -EPROBE_DEFER
> >       cpu cpu0: cpu0 regulator not ready, retry
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:371:
> > resources_available() returned -517
>
> we deferred probe once.
>
> >       ...
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:362
> >       cpu cpu0: resources_available:95
> >       cpu cpu0: resources_available:102: clk_get() returned z
> >       cpu cpu0: resources_available:120:
> > dev_pm_opp_of_find_icc_paths() returned 0
> >       cpu cpu0: resources_available:125: find_supply_name() returned cpu0
> >       cpu cpu0: resources_available:132: regulator_get_optional()
> > returned (ptrval)
>
> found regulator next time.
>
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:371:
> > resources_available() returned 0
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:375
> >       cpufreq_dt: cpufreq_init:162
> >       cpu cpu0: cpufreq_init:170: clk_get() returned z
> >       cpu cpu0: cpufreq_init:179: dev_pm_opp_of_get_sharing_cpus() returned -2
> >       cpu cpu0: cpufreq_init:198: find_supply_name() returned cpu0
> >       <i2c comm>
> >       cpu cpu0: cpufreq_init:201: dev_pm_opp_set_regulators() returned (ptrval)
> >       <i2c comm>
> >       cpu cpu0: cpufreq_init:230: dev_pm_opp_of_cpumask_add_table() returned 0
> >       cpu cpu0: cpufreq_init:239: dev_pm_opp_get_opp_count() returned 0
> >       cpu cpu0: OPP table is not ready, deferring probe
>
> This failed, as we couldn't have deferred probe from cpufreq_init.
> Which means that cpufreq didn't work here.

No opp-table in DT.
Shouldn't it use operating-points v1 instead?

> >       cpufreq_dt: cpufreq_init:162
> >       cpu cpu1: cpufreq_init:170: clk_get() returned z
> >       cpu cpu1: cpufreq_init:179: dev_pm_opp_of_get_sharing_cpus() returned -2
> >       cpu cpu1: no regulator for cpu1
> >       cpu cpu1: cpufreq_init:198: find_supply_name() returned (null)
> >       cpu cpu1: cpufreq_init:230: dev_pm_opp_of_cpumask_add_table() returned 0
> >       cpu cpu1: cpufreq_init:239: dev_pm_opp_get_opp_count() returned 0
> >       cpu cpu1: OPP table is not ready, deferring probe
>
> Same for CPU1.

Note that only CPU0 has operating-points v1.

>
> >
> >     s2ram:
> >       cpufreq_dt: cpufreq_init:162
> >       cpu cpu1: cpufreq_init:170: clk_get() returned z
> >       cpu cpu1: cpufreq_init:179: dev_pm_opp_of_get_sharing_cpus() returned -2
> >       cpu cpu1: no regulator for cpu1
> >       cpu cpu1: cpufreq_init:198: find_supply_name() returned (null)
> >       cpu cpu1: cpufreq_init:230: dev_pm_opp_of_cpumask_add_table() returned 0
> >       cpu cpu1: cpufreq_init:239: dev_pm_opp_get_opp_count() returned 0
> >       cpu cpu1: OPP table is not ready, deferring probe
>
> And same here.
>
> >       CPU1 is up
> >
> >   After:
> >     boot:
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:356
> >       cpufreq_dt: dt_cpufreq_early_init:251
> >       cpu cpu0: dt_cpufreq_early_init:256
> >       cpu cpu0: dt_cpufreq_early_init:271: dev_pm_opp_get_opp_table()
> > returned (ptrval)
> >       cpu cpu0: dt_cpufreq_early_init:284: find_supply_name() returned cpu0
> >       cpu cpu0: dt_cpufreq_early_init:288: dev_pm_opp_set_regulators()
> > returned -EPROBE_DEFER
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:360:
> > dt_cpufreq_early_init() returned -517
> >       ...
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:356
> >       cpufreq_dt: dt_cpufreq_early_init:251
> >       cpu cpu0: dt_cpufreq_early_init:256
> >       cpu cpu0: dt_cpufreq_early_init:271: dev_pm_opp_get_opp_table()
> > returned (ptrval)
> >       cpu cpu0: dt_cpufreq_early_init:284: find_supply_name() returned cpu0
> >       cpu cpu0: dt_cpufreq_early_init:288: dev_pm_opp_set_regulators()
> > returned (ptrval)
> >       cpu cpu0: dt_cpufreq_early_init:301:
> > dev_pm_opp_of_get_sharing_cpus() returned -2
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:360:
> > dt_cpufreq_early_init() returned 0
> >       cpufreq_dt: dt_cpufreq_early_init:251
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:360:
> > dt_cpufreq_early_init() returned 0
> >       cpufreq-dt cpufreq-dt: dt_cpufreq_probe:365
> >       cpufreq_dt: cpufreq_init:114
> >       cpu cpu0: cpufreq_init:124: clk_get() returned z
> >       cpu cpu0: cpufreq_init:142: dev_pm_opp_of_cpumask_add_table() returned 0
> >       cpu cpu0: cpufreq_init:151: dev_pm_opp_get_opp_count() returned 0
> >       cpu cpu0: OPP table can't be empty
>
> Same issue here.
>
> >       cpufreq_dt: cpufreq_init:114
> >       cpu cpu0: cpufreq_init:124: clk_get() returned z
> >       <i2c comm>
> >       cpu cpu0: cpufreq_init:142: dev_pm_opp_of_cpumask_add_table() returned 0
> >       cpu cpu0: cpufreq_init:151: dev_pm_opp_get_opp_count() returned 0
> >
> >     s2ram:
> >
> >       cpufreq_dt: cpufreq_init:114
> >       cpu cpu0: cpufreq_init:124: clk_get() returned z
> >       WARNING: CPU: 1 PID: 14 at drivers/i2c/i2c-core.h:54
> > __i2c_transfer+0x2d8/0x310
> >       i2c i2c-6: Transfer while suspended
> >       cpu cpu0: cpufreq_init:142: dev_pm_opp_of_cpumask_add_table() returned 0
> >       cpu cpu0: cpufreq_init:151: dev_pm_opp_get_opp_count() returned 0
> >       cpu cpu0: OPP table can't be empty
> >       CPU1 is up
> >
> > I hope this helps.
>
> Unfortunately it raised more questions than what it answered :(

Before, it bailed out before talking to the regulator during s2ram,
After, it talks to the regulator before bailing out, triggering the WARN().

1. Why is it bailing out without an opp-table, as operating-points (v1)
   is present?
2. Even in the presence of an opp-table, the code would talk to the
   PMIC while the I2C controller is suspended.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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