[PATCH 09/11] drm/i915/display: Enable interrupts earlier on PREEMPT_RT

[Maarten Lankhorst <dev@lankhorst.se>]

The last part of the vblank evasion is about updating bookkeeping,
not programming hardware registers.

The interrupts cannot stay disabled here on PREEMPT_RT since the
spinlocks get converted to mutexes.

There's still a small race in VRR that needs to be addressed, and
in the other worst case there is a delay of a vblank completion if
the vblank is fired and we schedule on the next vblank, this needs
to be addressed separately.

Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
---
 drivers/gpu/drm/i915/display/intel_crtc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_crtc.c b/drivers/gpu/drm/i915/display/intel_crtc.c
index 778ebc5095c38..93e58c12ac994 100644
--- a/drivers/gpu/drm/i915/display/intel_crtc.c
+++ b/drivers/gpu/drm/i915/display/intel_crtc.c
@@ -703,6 +703,14 @@ void intel_pipe_update_end(struct intel_atomic_state *state,
 	    intel_crtc_has_type(new_crtc_state, INTEL_OUTPUT_DSI))
 		icl_dsi_frame_update(new_crtc_state);
 
+#if IS_ENABLED(CONFIG_PREEMPT_RT)
+	/*
+	 * Timing sensitive register writing completed, non-deterministic
+	 * locking from here on out.
+	 */
+	local_irq_enable();
+#endif
+
 	/* We're still in the vblank-evade critical section, this can't race.
 	 * Would be slightly nice to just grab the vblank count and arm the
 	 * event outside of the critical section - the spinlock might spin for a
@@ -750,7 +758,9 @@ void intel_pipe_update_end(struct intel_atomic_state *state,
 	if (!state->base.legacy_cursor_update)
 		intel_vrr_send_push(NULL, new_crtc_state);
 
+#if !IS_ENABLED(CONFIG_PREEMPT_RT)
 	local_irq_enable();
+#endif
 
 	if (intel_parent_vgpu_active(display))
 		goto out;
-- 
2.51.0