linux-kernel - Re: [PATCH] drm/i915: Make vblank evade warnings optional

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Message-ID: <f66ffb96-3273-bdde-2594-1b6f85bf36ba@kernel.dk>
Date:   Sun, 7 May 2017 19:52:14 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     "Syrjala, Ville" <ville.syrjala@...ux.intel.com>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Dave Airlie <airlied@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Subject: Re: [PATCH] drm/i915: Make vblank evade warnings optional

On 05/07/2017 11:56 AM, Daniel Vetter wrote:
> On Sun, May 7, 2017 at 7:46 PM, Jens Axboe <axboe@...nel.dk> wrote:
>> On 05/07/2017 11:12 AM, ville.syrjala@...ux.intel.com wrote:
>>> From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>>>
>>> Add a new Kconfig option to enable/disable the extra warnings
>>> from the vblank evade code. For now we'll keep the warning
>>> about an actually missed vblank always enabled as that can have
>>> an actual user visible impact. But if we miss the deadline
>>> othrwise there's no real need to bother the user with that.
>>> We'll want these warnings enabled during development however
>>> so that we can catch regressions.
>>>
>>> Based on the reports it looks like this is still very easy
>>> to hit on SKL, so we have more work ahead of us to optimize
>>> the crtiical section further.
>>
>> Shouldn't it just be a debug printk or something instead, so that normal
>> people don't see it, but the folks that turn on debugging can get the
>> info they need? Seems silly to add a kconfig option for this.
> 
> I guess we could keep it as debug for users, but we want to make this
> a hard failure on our CI machines. Kconfig knob is the easiest to roll
> out to all machines.

Wouldn't a module parameter be more useful then, as an opt-in
to catch these violations.

Nobody is going to know wtf to set this kconfig option to.

-- 
Jens Axboe