linux-kernel - Re: git pull] drm for v4.1-rc1

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Date:	Sun, 7 Jun 2015 02:52:48 +0300
From:	Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:	Stefan Lippers-Hollmann <s.l-h@....de>
Cc:	Dave Airlie <airlied@...ux.ie>,
	Ander Conselvan de Oliveira 
	<ander.conselvan.de.oliveira@...el.com>,
	Nicolas Kalkhof <nkalkhof@....de>,
	Jani Nikula <jani.nikula@...el.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-kernel@...r.kernel.org,
	DRI mailing list <dri-devel@...ts.freedesktop.org>,
	torvalds@...ux-foundation.org
Subject: Re: git pull] drm for v4.1-rc1

On Fri, Jun 05, 2015 at 11:18:21PM +0200, Stefan Lippers-Hollmann wrote:
> Hi
> 
> On 2015-04-20, Dave Airlie wrote:
> [...]
> > The following changes since commit 09d51602cf84a1264946711dd4ea0dddbac599a1:
> > 
> >   Merge branch 'turbostat' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux (2015-04-19 14:31:41 -0700)
> > 
> > are available in the git repository at:
> > 
> >   git://people.freedesktop.org/~airlied/linux drm-next-merged
> > 
> > for you to fetch changes up to 2c33ce009ca2389dbf0535d0672214d09738e35e:
> > 
> >   Merge Linus master into drm-next (2015-04-20 13:05:20 +1000)
> [...]
> > Ander Conselvan de Oliveira (28):
> [...]
> >       drm/i915: Allocate connector state together with the connectors
> [...]
> 
> This commit introduces a regression relative to v4.0 on an Intel 
> D945GCLF2 mainboard[1] (Atom 330) with Intel 82945G/GZ onboard graphics 
> using its (only-) VGA connector for me.
> 
> v4.1-rc6-52-gff25ea8:
> [   13.265699] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> [   13.265723] IP: [<ffffffffa0556f01>] intel_modeset_update_connector_atomic_state+0x61/0x90 [i915]

Hmm. Smells like a connector with a NULL state pointer, and the bad
commit touched exactly the part that sets it up. I can't immediately
spot any place where we'd forget to set it up though.

Can you try with something like this so we'd at least find out which
connector(s) is/are at fault here?

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 3007b44..c10f423 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -918,6 +918,8 @@ int drm_connector_init(struct drm_device *dev,
 
 	connector->debugfs_entry = NULL;
 
+	WARN(1, "connector = %p\n", connector);
+
 out_put:
 	if (ret)
 		drm_mode_object_put(dev, &connector->base);
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index d0f3cbc..dd8ced7 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10332,6 +10332,10 @@ static void intel_modeset_update_connector_atomic_state(struct drm_device *dev)
 	struct intel_connector *connector;
 
 	for_each_intel_connector(dev, connector) {
+		if (WARN(!connector->base.state,
+			 "connector = %p\n", &connector->base))
+			continue;
+
 		if (connector->base.encoder) {
 			connector->base.state->best_encoder =
 				connector->base.encoder;
-- 
2.3.6

-- 
Ville Syrjälä
Intel OTC
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