From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paul Bolle <pebolle@tiscali.nl>
Subject: Re: [PATCH v2 1/3] drm/i915: Fix cdclk vs. dev_cdclk mess when not
 recomputing things
Date: Thu, 17 Nov 2016 09:17:42 +0100
Message-ID: <1479370662.19539.14.camel@tiscali.nl>
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Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Mika Kahola <mika.kahola@intel.com>, bruno.pagani@ens-lyon.org, Daniel J Blueman <daniel.blueman@gmail.com>, Joseph Yasi <joe.yasi@gmail.com>, stable@vger.kernel.org
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On Mon, 2016-11-14 at 18:35 +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> When we end up not recomputing the cdclk, we need to populate
> intel_state->cdclk with the "atomic_cdclk_freq" instead of the
> current cdclk_freq. When no pipes are active, the actual cdclk_freq
> may be lower than what the configuration of the planes and
> pipes would require from the point of view of the software state.
> 
> This fixes bogus WARNS from skl_max_scale() which is trying to check
> the plane software state against the cdclk frequency. So any time
> it got called during DPMS off for instance, we might have tripped
> the warn if the current mode would have required a higher than
> minimum cdclk.
> 
> v2: Drop the dev_cdclk stuff (Maarten)
> 
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Mika Kahola <mika.kahola@intel.com>
> Cc: bruno.pagani@ens-lyon.org
> Cc: Daniel J Blueman <daniel.blueman@gmail.com>
> Cc: Paul Bolle <pebolle@tiscali.nl>
> Cc: Joseph Yasi <joe.yasi@gmail.com>
> Tested-by: Paul Bolle <pebolle@tiscali.nl> (v1)

I've run v2 of this patch (on top of v4.8.8) for over a day now without
hitting the WARN_ON_ONCE. Of course, my machine was suspended for large parts
of that period. But still, the WARN_ON_ONCE used to be triggered much quicker.
So in short: you can drop "(v1)" as I tested both versions now.

By the way, the scary i915 *ERROR*s are gone now too, as are the visual
glitches that accompanied those *ERROR*s. Apparently the v4.8.y series picked
up a few fixes. Those made i915 a much better experience. Nice! 

> Tested-by: Joseph Yasi <joe.yasi@gmail.com> (v1)
> Cc: stable@vger.kernel.org
> Fixes: 1a617b77658e ("drm/i915: Keep track of the cdclk as if all crtc's were active.")

(I seem to remember discussing the reasons why a v4.6 bug was first noticed on
v4.8. I haven't looked into that yet. By now it's unlikely I ever will. Sorry
about that.)

> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98214
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

Thanks,


Paul Bolle