drm/i915: Add transcoder restriction to PSR2

According to PSR2_CTL definition in BSpec there is only one instance
of PSR2_CTL. Platforms gen < 12 with EDP transcoder only support PSR2
on TRANSCODER_EDP while on TGL PSR2 is only supported by
TRANSCODER_A.

Since BDW PSR is allowed on any port, but we need to restrict by
transcoder.

v8: Renamed _psr2_supported_in_trans() to psr2_supported() (Lucas)

v9: Renamed psr2_supported() to transcoder_has_psr2() (Ville)

BSpec: 7713
BSpec: 20584
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190820223325.27490-2-jose.souza@intel.com

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

@@ -534,6 +534,15 @@ static void hsw_activate_psr2(struct intel_dp *intel_dp)
 	I915_WRITE(EDP_PSR2_CTL(dev_priv->psr.transcoder), val);
 }
 
+static bool
+transcoder_has_psr2(struct drm_i915_private *dev_priv, enum transcoder trans)
+{
+	if (INTEL_GEN(dev_priv) >= 12)
+		return trans == TRANSCODER_A;
+	else
+		return trans == TRANSCODER_EDP;
+}
+
 static bool intel_psr2_config_valid(struct intel_dp *intel_dp,
 				    struct intel_crtc_state *crtc_state)
 {
@@ -545,6 +554,12 @@ static bool intel_psr2_config_valid(struct intel_dp *intel_dp,
 	if (!dev_priv->psr.sink_psr2_support)
 		return false;
 
+	if (!transcoder_has_psr2(dev_priv, crtc_state->cpu_transcoder)) {
+		DRM_DEBUG_KMS("PSR2 not supported in transcoder %s\n",
+			      transcoder_name(crtc_state->cpu_transcoder));
+		return false;
+	}
+
 	/*
 	 * DSC and PSR2 cannot be enabled simultaneously. If a requested
 	 * resolution requires DSC to be enabled, priority is given to DSC