linux-kernel - Re: [PATCH v2 00/10] Exynos IOMMU: proper runtime PM support (use device dependencies)

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Date:	Tue, 19 Jul 2016 08:26:20 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc:	Joerg Roedel <joro@...tes.org>, Inki Dae <inki.dae@...sung.com>,
	Kukjin Kim <kgene@...nel.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 00/10] Exynos IOMMU: proper runtime PM support (use
 device dependencies)

Hi Tobias


On 2016-07-18 18:43, Tobias Jakobi wrote:
> Marek Szyprowski wrote:
>> On 2016-07-18 13:00, Tobias Jakobi wrote:
>>> Marek Szyprowski wrote:
>>>> On 2016-07-15 15:21, Tobias Jakobi wrote:
>>>>> Tobias Jakobi wrote:
>>>>>> Hello Marek,
>>>>>>
>>>>>> I've tested the patchset on 4.7-rc7 and noticed that it breaks
>>>>>> reboot on
>>>>>> my ODROID-X2.
>>>>>>
>>>>>> Going to check where exactly things break.
>>>>> Sadly it's the last patch where everything comes together:
>>>>> "iommu/exynos: Add proper runtime pm support"
>>>>>
>>>>> I still have to check if forcing runpm status to 'on' makes a
>>>>> difference. I suspect that the aggressive clock gating might be the
>>>>> reason?
>>>> Thanks for testing. I will check this issue. Could you send me your
>>>> .config?
>>> This is the config I'm currently using:
>>> https://github.com/tobiasjakobi/odroid-environment/blob/master/sourcecode/system/vanilla-4.7-debug.conf
>>>
>>>
>>> Do you think checking this with no_console_suspend makes sense?
>> no_console_suspend switch won't provide more information, but I managed
>> to reproduce your issue. I'm really confused how enabling runtime pm can
>> cause problems with usb/smsc95xx ethernet driver (that is the reason for
>> failed reboot). Maybe it is somehow related to the global relations
>> between devices and drivers and the fact that creating the runtime pm
>> links change the order of operations. I will check this again when
>> Rafael send updated patches. Here is the log I got (after waiting some
>> time):
> thanks for looking into this! I'll try to reproduce this on my board. I
> have to admit that I didn't wait too long for the hung task message to
> appear.
>
> I wonder if this has something to do with regulator code cutting some
> supplies too early. Is this on a X2 or a U2/U3?

I've reproduced it on U3.

> I'm not sure if we
> currently model the regulator setup correctly here (IIRC then buck8 is
> supplying the LAN/USB block on U2/U3).

IMHO it is not really related to regulator operations, but the sequence
of shutting down logical devices in the system. For some reasons when pm 
links
are used, something changes the order of operations in system shutdown
procedure, what causes smsc95xx to hang. I have no idea why, but I don't 
have
time to investigate it further. I will wait for the next release of Rafael's
pm links patches and then check everything again.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland