[PATCH 33/43] drm/i915: WARN when trying to enabled an unused crtc

[Daniel Vetter <daniel.vetter@ffwll.ch>]

This is the first tiny step towards cross-checking the entire modeset
state machine with WARNs. A crtc can only be enabled when it's
actually in use, i.e. crtc->active imlies crtc->enabled.

Unfortunately we can't (yet) check this when disabling the crtc,
because the crtc helpers are a bit slopy with updating state and
unconditionally update crtc->enabled before changing the hw state.

Fixing that requires quite some more work.

Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_display.c |    4 ++++
 drivers/gpu/drm/i915/intel_drv.h     |   10 +++++++++-
 2 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 0c4eca5..e01cd09 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3153,6 +3153,8 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 	u32 temp;
 	bool is_pch_port;
 
+	WARN_ON(!crtc->enabled);
+
 	/* XXX: For compatability with the crtc helper code, call the encoder's
 	 * enable function unconditionally for now. */
 	if (intel_crtc->active)
@@ -3348,6 +3350,8 @@ static void i9xx_crtc_enable(struct drm_crtc *crtc)
 	int pipe = intel_crtc->pipe;
 	int plane = intel_crtc->plane;
 
+	WARN_ON(!crtc->enabled);
+
 	/* XXX: For compatability with the crtc helper code, call the encoder's
 	 * enable function unconditionally for now. */
 	if (intel_crtc->active)
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 70a8e10..8714f00 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -156,7 +156,15 @@ struct intel_crtc {
 	enum plane plane;
 	u8 lut_r[256], lut_g[256], lut_b[256];
 	int dpms_mode;
-	bool active; /* is the crtc on? independent of the dpms mode */
+	/*
+	 * Whether the crtc and the connected output pipeline is active. Implies
+	 * that crtc->enabled is set, i.e. the current mode configuration has
+	 * some outputs connected to this crtc.
+	 *
+	 * Atm crtc->enabled is unconditionally updated _before_ the hw state is
+	 * changed, hence we can only check this when enabling the crtc.
+	 */
+	bool active;
 	bool primary_disabled; /* is the crtc obscured by a plane? */
 	bool busy; /* is scanout buffer being updated frequently? */
 	struct timer_list idle_timer;
-- 
1.7.7.6