linux-kernel - Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time

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Date:   Mon, 27 Apr 2020 17:13:56 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Manikanta Maddireddy <mmaddireddy@...dia.com>,
        Vidya Sagar <vidyas@...dia.com>
Cc:     linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy
 for a long time

27.04.2020 15:46, Dmitry Osipenko пишет:
> 23.04.2020 13:56, Jon Hunter пишет:
>>>> So I think that part of the problem already existed prior to these
>>>> patches. Without your patches I see ...
>>>>
>>>> [   59.543528] tegra-i2c 7000d000.i2c: i2c transfer timed out
>>>> [   59.549036] vdd_sata,avdd_plle: failed to disable
>>>> [   59.553778] Failed to disable avdd-plle: -110
>>>> [   59.558150] tegra-pcie 3000.pcie: failed to disable regulators: -110
>>> Does this I2C timeout happen with my patches? Could you please post full
>>> logs of an older and the recent kernel versions?
>> I believe that it does, but I need to check.
>>
> 
> Jon, could you please confirm that you're seeing those regulator-disable
> errors with my patch? I don't see those errors in yours original log [1].
> 
> [1]
> https://lore.kernel.org/lkml/1e259e22-c300-663a-e537-18d854e0f478@nvidia.com/
> 
> Again, could you please post the *full* logs?
> 
> If regulator's disabling was "failing" before without my patch because
> of the I2C interrupt being force-disabled during of NOIRQ phase, and now
> regulator's disabling succeeds with my patch because IRQ is manually
> handled after the timeout, then this could be bad. It means that
> regulator was actually getting disabled, but I2C driver was timing out
> because interrupt couldn't be handled in NOIRQ phase, which should
> result in a dead PCIe on a resume from suspend since regulator's core
> thinks that regulator is enabled (I2C said it failed to disable), while
> it is actually disabled.
> 
> Do you have anything plugged into the PCIe slot in yours testing farm?
> It wouldn't surprise me if the plugged card isn't functional after
> resume from suspend on a stable kernels.
> 

I actually now see that interrupt is not allowed to be enabled during
the NOIRQ phase:

https://elixir.bootlin.com/linux/v5.7-rc3/source/kernel/irq/manage.c#L640

it should be worthwhile to turn it into a WARN_ON.