drm/i915: Configure TRANS_SET_CONTEXT_LATENCY correctly on ADL+

On TGL VBLANK.VBLANK_START was the mechanism by which we can
delay the pipe's internal vblank in relation to the transcoder's
vblank. On ADL+ that no longer does anything. Instead we must
now use the new TRANS_SET_CONTEXT_LATENCY register. Program it
accordingly.

And since VBLANK.VBLANK_START is no longer used by the hardware
on ADL+ let's just zero it out to make it stand out in register
dumps. Seeing the zeroed value should hopefully remind people
to check the other register instead.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230213225258.2127-11-ville.syrjala@linux.intel.comAcked-by: Jani Nikula <jani.nikula@intel.com>

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

@@ -2724,12 +2724,14 @@ static void intel_set_transcoder_timings(const struct intel_crtc_state *crtc_sta
 	enum pipe pipe = crtc->pipe;
 	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
 	const struct drm_display_mode *adjusted_mode = &crtc_state->hw.adjusted_mode;
-	u32 crtc_vtotal, crtc_vblank_end;
+	u32 crtc_vdisplay, crtc_vtotal, crtc_vblank_start, crtc_vblank_end;
 	int vsyncshift = 0;
 
 	/* We need to be careful not to changed the adjusted mode, for otherwise
 	 * the hw state checker will get angry at the mismatch. */
+	crtc_vdisplay = adjusted_mode->crtc_vdisplay;
 	crtc_vtotal = adjusted_mode->crtc_vtotal;
+	crtc_vblank_start = adjusted_mode->crtc_vblank_start;
 	crtc_vblank_end = adjusted_mode->crtc_vblank_end;
 
 	if (adjusted_mode->flags & DRM_MODE_FLAG_INTERLACE) {
@@ -2746,6 +2748,21 @@ static void intel_set_transcoder_timings(const struct intel_crtc_state *crtc_sta
 			vsyncshift += adjusted_mode->crtc_htotal;
 	}
 
+	/*
+	 * VBLANK_START no longer works on ADL+, instead we must use
+	 * TRANS_SET_CONTEXT_LATENCY to configure the pipe vblank start.
+	 */
+	if (DISPLAY_VER(dev_priv) >= 13) {
+		intel_de_write(dev_priv, TRANS_SET_CONTEXT_LATENCY(cpu_transcoder),
+			       crtc_vblank_start - crtc_vdisplay);
+
+		/*
+		 * VBLANK_START not used by hw, just clear it
+		 * to make it stand out in register dumps.
+		 */
+		crtc_vblank_start = 1;
+	}
+
 	if (DISPLAY_VER(dev_priv) > 3)
 		intel_de_write(dev_priv, TRANS_VSYNCSHIFT(cpu_transcoder),
 			       vsyncshift);
@@ -2761,10 +2778,10 @@ static void intel_set_transcoder_timings(const struct intel_crtc_state *crtc_sta
 		       HSYNC_END(adjusted_mode->crtc_hsync_end - 1));
 
 	intel_de_write(dev_priv, TRANS_VTOTAL(cpu_transcoder),
-		       VACTIVE(adjusted_mode->crtc_vdisplay - 1) |
+		       VACTIVE(crtc_vdisplay - 1) |
 		       VTOTAL(crtc_vtotal - 1));
 	intel_de_write(dev_priv, TRANS_VBLANK(cpu_transcoder),
-		       VBLANK_START(adjusted_mode->crtc_vblank_start - 1) |
+		       VBLANK_START(crtc_vblank_start - 1) |
 		       VBLANK_END(crtc_vblank_end - 1));
 	intel_de_write(dev_priv, TRANS_VSYNC(cpu_transcoder),
 		       VSYNC_START(adjusted_mode->crtc_vsync_start - 1) |
@@ -2852,6 +2869,11 @@ static void intel_get_transcoder_timings(struct intel_crtc *crtc,
 		adjusted_mode->crtc_vtotal += 1;
 		adjusted_mode->crtc_vblank_end += 1;
 	}
+
+	if (DISPLAY_VER(dev_priv) >= 13 && !transcoder_is_dsi(cpu_transcoder))
+		adjusted_mode->crtc_vblank_start =
+			adjusted_mode->crtc_vdisplay +
+			intel_de_read(dev_priv, TRANS_SET_CONTEXT_LATENCY(cpu_transcoder));
 }
 
 static void intel_bigjoiner_adjust_pipe_src(struct intel_crtc_state *crtc_state)