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

From: Dmitry Osipenko <digetx@gmail.com>
To: Jon Hunter <jonathanh@nvidia.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Laxman Dewangan <ldewangan@nvidia.com>,
	Wolfram Sang <wsa@the-dreams.de>,
	Manikanta Maddireddy <mmaddireddy@nvidia.com>,
	Vidya Sagar <vidyas@nvidia.com>
Cc: linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time
Date: Mon, 27 Apr 2020 17:45:26 +0300	[thread overview]
Message-ID: <090241c4-e026-aea4-e1e9-a2a661b2c27e@gmail.com> (raw)
In-Reply-To: <5fc71168-e4ac-11f6-dbf1-e80f4fae8d1a@gmail.com>

27.04.2020 17:13, Dmitry Osipenko пишет:
> 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.
> 

Oh, wait! There is already a warning there.. hmm.