From: Paul Kocialkowski <paul.kocialkowski@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@linux.ie>, Daniel Vetter <daniel.vetter@intel.com>
Subject: Re: [PATCH i-g-t 1/2] tests/chamelium: Skip suspend/resume test with unreliable hotplug event
Date: Wed, 19 Jul 2017 11:31:39 +0300 [thread overview]
Message-ID: <1500453099.1329.1.camel@linux.intel.com> (raw)
In-Reply-To: <150041286733.27297.6538270479541507952@mail.alporthouse.com>
On Tue, 2017-07-18 at 22:21 +0100, Chris Wilson wrote:
> Quoting Paul Kocialkowski (2017-07-18 16:16:26)
> > It may occur that a hotplug uevent is detected at resume, even
> > though it
> > does not indicate that an actual hotplug happened. This is the case
> > when
> > link training fails on any other connector.
> >
> > There is currently no way to distinguish what connector caused a
> > hotplug
> > uevent, nor what the reason for that uevent really is. This makes it
> > impossible to find out whether the test actually passed or not.
>
> And you may get more than one and then this skips even though the test
> passed. Looks like the patch is overcompensating. What you can do is
> repeat the test a few times, and then look at all the different errors
> you get. If the connector remains (no mst disappareance) once it goes
> bad, it should remain bad and so not generate any new uevent. Or you
> only repeat the test whilst link_status[old] != link_status[new].
I am not sure it is really desirable to repeat the test until we are
fairly certain it succeeds. This involves suspend/resume, that is
already long enough as it is.
Also, a uevent will be generated everytime link training fails,
regardless of whether it was already failing before (I just tested that
to make sure). In my case, it's due to a DP-VGA bridge that will
consistently fail link training in the first seconds after resume.
So this is actually even worse that I thought, because there is no way
to find out that this is why a uevent was generated if the link status
was already bad before.
So I don't see how we can manage with the current information at
disposal.
My main point here is that we need more information about what's going
on than simply "HOTPLUG=1". These patches demonstrate that working
around the lack of information is a pain for testing purposes and can
only leads to semi-working hackish workarounds.
Do you agree that this is what the problem really is?
--
Paul Kocialkowski <paul.kocialkowski@linux.intel.com>
Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo, Finland
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next prev parent reply other threads:[~2017-07-19 8:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-18 15:16 [PATCH i-g-t 0/2] Unrelated hotplug uevent masking out actual test result Paul Kocialkowski
2017-07-18 15:16 ` [PATCH i-g-t 1/2] tests/chamelium: Skip suspend/resume test with unreliable hotplug event Paul Kocialkowski
2017-07-18 21:21 ` Chris Wilson
2017-07-19 8:31 ` Paul Kocialkowski [this message]
2017-07-19 15:47 ` Lyude Paul
2017-07-18 15:16 ` [PATCH i-g-t 2/2] tests/chamelium: Catch and flush hotplug uevents after each plug Paul Kocialkowski
2017-07-18 20:12 ` [Intel-gfx] [PATCH i-g-t 0/2] Unrelated hotplug uevent masking out actual test result Lyude Paul
-- strict thread matches above, loose matches on Subject: below --
2017-07-18 15:15 [PATCH i-g-t 1/2] tests/chamelium: Skip suspend/resume test with unreliable hotplug event Paul Kocialkowski
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