drm/i915/dsb: Introduce intel_dsb_wait_vblank_delay()

Add intel_dsb_wait_vblank_delay() which instructs the DSB
to wait for duration between the undelayed and delayed vblanks.
We'll need this as the DSB can only directly wait for the
undelayed vblank, but we'll need to wait until the delayed
vblank has elapsed as well.

Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240930170415.23841-10-ville.syrjala@linux.intel.com

Author: vsyrjala

drivers/gpu/drm/i915/display/intel_dsb.c

@@ -637,6 +637,17 @@ void intel_dsb_chain(struct intel_atomic_state *state,
 			 wait_for_vblank ? DSB_WAIT_FOR_VBLANK : 0);
 }
 
+void intel_dsb_wait_vblank_delay(struct intel_atomic_state *state,
+				 struct intel_dsb *dsb)
+{
+	struct intel_crtc *crtc = dsb->crtc;
+	const struct intel_crtc_state *crtc_state = pre_commit_crtc_state(state, crtc);
+	int usecs = intel_scanlines_to_usecs(&crtc_state->hw.adjusted_mode,
+					     dsb_vblank_delay(crtc_state)) + 1;
+
+	intel_dsb_wait_usec(dsb, usecs);
+}
+
 static void _intel_dsb_commit(struct intel_dsb *dsb, u32 ctrl,
 			      int hw_dewake_scanline)
 {

drivers/gpu/drm/i915/display/intel_dsb.h

@@ -42,6 +42,8 @@ void intel_dsb_nonpost_end(struct intel_dsb *dsb);
 void intel_dsb_interrupt(struct intel_dsb *dsb);
 void intel_dsb_wait_usec(struct intel_dsb *dsb, int count);
 void intel_dsb_wait_vblanks(struct intel_dsb *dsb, int count);
+void intel_dsb_wait_vblank_delay(struct intel_atomic_state *state,
+				 struct intel_dsb *dsb);
 void intel_dsb_wait_scanline_in(struct intel_atomic_state *state,
 				struct intel_dsb *dsb,
 				int lower, int upper);