Subject: Re: 4.0.8->4.1.3 : after resume from s2ram both internal and external
 display of a docked ThinkPad ate black
To: Pavel Machek <pavel@ucw.cz>
References: <55B8DAF8.6070805@gmx.de> <20150802074334.GG3720@amd>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Dave Airlie <airlied@redhat.com>
From: =?UTF-8?Q?Toralf_F=c3=b6rster?= <toralf.foerster@gmx.de>
Message-ID: <55C0B038.8090807@gmx.de>
Date: Tue, 4 Aug 2015 14:29:44 +0200
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On 08/02/2015 09:43 AM, Pavel Machek wrote:
> Any chance to bisect it?
Did it.

FWIW: the mentioned commit was introduced between 3.18 and 3.19.
But my system (hardened 64 bit Gentoo) did not suffer from it till version 4.0.8.
The hardened kernel 4.1.x was the first where the bug was visible at my docked environment  too.


commit e7d6f7d708290da1b7c92f533444b042c79412e0
Author: Dave Airlie <airlied@redhat.com>
Date:   Mon Dec 8 13:23:37 2014 +1000

    drm/i915: resume MST after reading back hw state

    Otherwise the MST resume paths can hit DPMS paths
    which hit state checker paths, which hit WARN_ON,
    because the state checker is inconsistent with the
    hw.

    This fixes a bunch of WARN_ON's on resume after
    undocking.

    Signed-off-by: Dave Airlie <airlied@redhat.com>
    Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    Cc: stable@vger.kernel.org
    Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 1e9c136..f990ab4 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -706,11 +706,12 @@ static int i915_drm_resume(struct drm_device *dev)
                        dev_priv->display.hpd_irq_setup(dev);
                spin_unlock_irq(&dev_priv->irq_lock);

-               intel_dp_mst_resume(dev);
                drm_modeset_lock_all(dev);
                intel_modeset_setup_hw_state(dev, true);
                drm_modeset_unlock_all(dev);

+               intel_dp_mst_resume(dev);
+
                /*
                 * ... but also need to make sure that hotplug processing
                 * doesn't cause havoc. Like in the driver load code we don't


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