drm/i915/vrr: Generate VRR "safe window" for DSB

Looks like TRANS_CHICKEN bit 31 means something totally different
depending on the platform:
TGL: generate VRR "safe window" for DSB
ADL/DG2: make TRANS_SET_CONTEXT_LATENCY effective with VRR

So far we've only set this on ADL/DG2, but when using DSB+VRR
we also need to set it on TGL.

And a quick test on MTL says it doesn't need this bit for either
of those purposes, even though it's still documented as valid
in bspec.

Cc: stable@vger.kernel.org
Fixes: 34d8311f ("drm/i915/dsb: Re-instate DSB for LUT updates")
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9927Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240306040806.21697-2-ville.syrjala@linux.intel.comReviewed-by: Animesh Manna <animesh.manna@intel.com>

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

@@ -187,10 +187,11 @@ void intel_vrr_set_transcoder_timings(const struct intel_crtc_state *crtc_state)
 	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
 
 	/*
-	 * TRANS_SET_CONTEXT_LATENCY with VRR enabled
-	 * requires this chicken bit on ADL/DG2.
+	 * This bit seems to have two meanings depending on the platform:
+	 * TGL: generate VRR "safe window" for DSB vblank waits
+	 * ADL/DG2: make TRANS_SET_CONTEXT_LATENCY effective with VRR
 	 */
-	if (DISPLAY_VER(dev_priv) == 13)
+	if (IS_DISPLAY_VER(dev_priv, 12, 13))
 		intel_de_rmw(dev_priv, CHICKEN_TRANS(cpu_transcoder),
 			     0, PIPE_VBLANK_WITH_DELAY);
 

drivers/gpu/drm/i915/i915_reg.h

@@ -4599,7 +4599,7 @@
 #define MTL_CHICKEN_TRANS(trans)	_MMIO_TRANS((trans), \
 						    _MTL_CHICKEN_TRANS_A, \
 						    _MTL_CHICKEN_TRANS_B)
-#define   PIPE_VBLANK_WITH_DELAY	REG_BIT(31) /* ADL/DG2 */
+#define   PIPE_VBLANK_WITH_DELAY	REG_BIT(31) /* tgl+ */
 #define   SKL_UNMASK_VBL_TO_PIPE_IN_SRD	REG_BIT(30) /* skl+ */
 #define   HSW_FRAME_START_DELAY_MASK	REG_GENMASK(28, 27)
 #define   HSW_FRAME_START_DELAY(x)	REG_FIELD_PREP(HSW_FRAME_START_DELAY_MASK, x)