drm/i915: Track whether an atomic transaction changes the active CRTC's

For the purposes of DDB re-allocation we need to know whether a
transaction changes the list of CRTC's that are active.  While
state->modeset could be used for this purpose, that would be slightly
too aggressive since it would lead us to re-allocate the DDB when a
CRTC's mode changes, but not its final active state.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463061971-19638-7-git-send-email-matthew.d.roper@intel.com
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index db350e5..9f9c9cb8 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -291,6 +291,16 @@
 
 	bool dpll_set, modeset;
 
+	/*
+	 * Does this transaction change the pipes that are active?  This mask
+	 * tracks which CRTC's have changed their active state at the end of
+	 * the transaction (not counting the temporary disable during modesets).
+	 * This mask should only be non-zero when intel_state->modeset is true,
+	 * but the converse is not necessarily true; simply changing a mode may
+	 * not flip the final active status of any CRTC's
+	 */
+	unsigned int active_pipe_changes;
+
 	unsigned int active_crtcs;
 	unsigned int min_pixclk[I915_MAX_PIPES];