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Subject: Re: [PATCH v13 06/35] clk: tegra: Support runtime PM and power domain
From:   Dmitry Osipenko <digetx@gmail.com>
To:     Ulf Hansson <ulf.hansson@linaro.org>
Cc:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
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Date:   Wed, 6 Oct 2021 05:40:02 +0300
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06.10.2021 01:43, Dmitry Osipenko пишет:
> 06.10.2021 01:19, Dmitry Osipenko пишет:
> ...
>> I reproduced the OFF problem by removing the clk prepare/unprepare from
>> the suspend/resume of the clk driver and making some extra changes to
>> clock tree topology and etc to trigger the problem on Nexus 7.
>>
>> tegra-pmc 7000e400.pmc: failed to turn off PM domain heg: -13
>>
>> It happens from genpd_suspend_noirq() -> tegra_genpd_power_off() -> clk
>> -> GENPD -> I2C -> runtime-pm.
>>
>> -13 is EACCES, it comes from the runtime PM of I2C device. RPM is
>> prohibited/disabled during late (NOIRQ) suspend by the drivers core.
> 
> My bad, I double-checked and it's not I2C RPM that is failing now, but
> the clock's RPM [1], which is also unavailable during NOIRQ.
> 
> [1]
> https://elixir.free-electrons.com/linux/v5.15-rc4/source/drivers/clk/clk.c#L116
> 
> Previously it was I2C RPM that was failing in a similar way, but code
> changed a tad since that time.
> 

Just in case, I checked that the suspension order isn't somehow the
source of the problem by adding links to device tree in order to always
suspend clocks after the rest of devices and still GENPD gets -EACCESS
from clk_pm_runtime_get().

RPM is disabled by dpm_suspend_late(), which is invoked before
dpm_suspend_noirq() [1]. Hence RPM is unavailable in NOIRQ phase in any
case.

[1]
https://elixir.bootlin.com/linux/v5.15-rc4/source/kernel/power/suspend.c#L399