[PATCH v2] drm/i915: Do a better job at disabling primary plane in the noatomic case.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 13-11-15 om 14:28 schreef Ander Conselvan De Oliveira:
> On Thu, 2015-11-12 at 14:58 +0100, Maarten Lankhorst wrote:
>> Op 12-11-15 om 14:37 schreef Ander Conselvan De Oliveira:
>>> On Wed, 2015-11-11 at 15:36 +0100, Maarten Lankhorst wrote:
>>>> When disable_noatomic is called plane_mask is not reliable yet,
>>>> and plane_state->visible = true even after disabling the primary plane.
>>> So the stale value of plane_state->visible causes a subsequent modeset to
>>> enable
>>> the primary again?
>> Probably not because it would get recalculated in calc_changes, but it should
>> really be set to false afterwards.
> So basically I didn't understand how the wrong value of plane_state->visible
> causes the bug that was mentioned. I think a brief explanation in the commit
> message would be good.
Well, apply with git am --scissors. Same patch but mentioning this.

Is this better?
---->8-----

When disable_noatomic is called plane_mask is not correct yet,
and plane_state->visible = true is left as true after disabling
the primary plane.

Other planes are already disabled as part of crtc sanitization, only the
primary is left active. But the plane_mask is not updated here. It gets updated
during fb takeover in modeset_gem_init, or set to the new value on resume.

This means that to disable the primary plane 1 << drm_plane_index(primary)
needs to be used.

Afterwards because the crtc is no longer active it's forbidden to keep
plane_state->visible set, or a WARN_ON in intel_plane_atomic_calc_changes
triggers. There are other code points that rely on accurate plane_state->visible
too, so make sure the bool is cleared.


The other planes are already disabled in intel_sanitize_crtc, so
they don't have to be handled here.

Cc: stable@vger.kernel.org #v4.3, v4.2?
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92655
Tested-by: Tomas Mezzadra <tmezzadra@gmail.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b5f7493213b7..bc3282ab5ed2 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6267,9 +6267,11 @@ static void intel_crtc_disable_noatomic(struct drm_crtc *crtc)
 		WARN_ON(intel_crtc->unpin_work);
 
 		intel_pre_disable_primary(crtc);
+
+		intel_crtc_disable_planes(crtc, 1 << drm_plane_index(crtc->primary));
+		to_intel_plane_state(crtc->primary->state)->visible = false;
 	}
 
-	intel_crtc_disable_planes(crtc, crtc->state->plane_mask);
 	dev_priv->display.crtc_disable(crtc);
 	intel_crtc->active = false;
 	intel_update_watermarks(crtc);
-- 2.1.0