Re: [igt-dev] [PATCH i-g-t] igt/kms_frontbuffer_tracking: Skip tests if FBC was disabled

From: Jani Nikula <jani.nikula@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	"Lofstedt, Marta" <marta.lofstedt@intel.com>,
	"igt-dev@lists.freedesktop.org" <igt-dev@lists.freedesktop.org>
Cc: "Lankhorst, Maarten" <maarten.lankhorst@intel.com>
Subject: Re: [igt-dev] [PATCH i-g-t] igt/kms_frontbuffer_tracking: Skip tests if FBC was disabled
Date: Tue, 06 Mar 2018 12:55:02 +0200	[thread overview]
Message-ID: <87a7vlscc9.fsf@intel.com> (raw)
In-Reply-To: <152033311583.17960.7533094600459721936@mail.alporthouse.com>

On Tue, 06 Mar 2018, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Quoting Lofstedt, Marta (2018-03-06 10:39:04)
>> 
>> 
>> > -----Original Message-----
>> > From: Chris Wilson [mailto:chris@chris-wilson.co.uk]
>> > Sent: Tuesday, March 6, 2018 11:32 AM
>> > To: Lofstedt, Marta <marta.lofstedt@intel.com>; igt-
>> > dev@lists.freedesktop.org
>> > Subject: Re: [igt-dev] [PATCH i-g-t] igt/kms_frontbuffer_tracking: Skip tests if
>> > FBC was disabled
>> > 
>> > Quoting Marta Lofstedt (2018-03-06 09:24:57)
>> > > If FBC has been disabled in the system due to previous malfuction, we
>> > > would save time on CI if we bail out early.
>> > >
>> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105359
>> > > Signed-off-by: Marta Lofstedt <marta.lofstedt@intel.com>
>> > 
>> > Hmm, FBC starts inactive on a system, so we would need to ensure that we
>> > enabled FBC and did a proper modeset first and wait for FBC to be enabled
>> > first.
>> 
>> On the SKL NUCi5 system I have been running this on, the FBC disabled sysfs, isn't re-set after a modeset. Maybe this is a driver error that should not be hidden by me suggesting to skip the tests. 
>
> It may just be that we see the same error. Some errors like underruns
> permanently disable FBC (afaik).

Could we add a way to manually force enable FBC in that case? debugfs?

BR,
Jani.

>  
>> On the other hand, the kms_frontbuffer_tracking test should give different results if FBC is disabled compared to timeout in the fbc_wait_until_enabled() which up until some time ago was the most common way to fail this test. 
>
> I agree. It's just the test has to assume it is starting from scratch,
> so needs to put the system into a known state before it can deduce what
> is supported. So I think if we set the test mode inside setup_modeset(),
> we can then test whether FBC is supported on that mode.
> -Chris

-- 
Jani Nikula, Intel Open Source Technology Center
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