drm/i915/cmtg: Add intel_cmtg_is_allowed() for CMTG

CMTG is supported on transcoder A and transcoder B with EDP,
so add a separate helper intel_cmtg_is_allowed() to check the
prerequisites for enabling CMTG. CMTG will be enabled only in
specific use cases such as PSR2, PR-ALPM, and LOBF, and will be
used in conjunction with the DC3CO feature. DC3co will be enabled
in a separate patch.

Note: Use-case-specific checks and transcoder-port compatibility
validation will be handled part of DC3co feature implementation.

v2:
- Remove separate flag for DC3co from crtc_state. [Uma, Dibin]

v3:
- Do not access power domain members directly. [Jani]

v4:
- Remove check for DC3co state now. if needed add Dc3co allow check
later once Dc3co patches are merged. [Uma]

Bspec: 68915
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Dibin Moolakadan Subrahmanian <dibin.moolakadan.subrahmanian@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patch.msgid.link/20260615200339.885190-2-animesh.manna@intel.com

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

@@ -4,7 +4,6 @@
  */
 
 #include <linux/string_choices.h>
-#include <linux/types.h>
 
 #include <drm/drm_device.h>
 #include <drm/drm_print.h>
@@ -16,6 +15,7 @@
 #include "intel_display_device.h"
 #include "intel_display_power.h"
 #include "intel_display_regs.h"
+#include "intel_display_types.h"
 
 /**
  * DOC: Common Primary Timing Generator (CMTG)
@@ -185,3 +185,15 @@ void intel_cmtg_sanitize(struct intel_display *display)
 
 	intel_cmtg_disable(display, &cmtg_config);
 }
+
+bool intel_cmtg_is_allowed(const struct intel_crtc_state *crtc_state)
+{
+	struct intel_display *display = to_intel_display(crtc_state);
+	enum transcoder cpu_transcoder = crtc_state->cpu_transcoder;
+
+	if ((cpu_transcoder == TRANSCODER_A || cpu_transcoder == TRANSCODER_B) &&
+	    DISPLAY_VER(display) == 35 && intel_crtc_has_type(crtc_state, INTEL_OUTPUT_EDP))
+		return true;
+
+	return false;
+}

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

@@ -6,8 +6,12 @@
 #ifndef __INTEL_CMTG_H__
 #define __INTEL_CMTG_H__
 
+#include <linux/types.h>
+
 struct intel_display;
+struct intel_crtc_state;
 
 void intel_cmtg_sanitize(struct intel_display *display);
+bool intel_cmtg_is_allowed(const struct intel_crtc_state *crtc_state);
 
 #endif /* __INTEL_CMTG_H__ */