drm/i915/mtl: Skip PLL state verification in TBT mode

In TBT-alt mode the driver doesn't program the PHY's PLL, which is
handled instead by Thunderbolt driver/FW components, hence the PLL's HW
vs. SW state verification should be skipped. During HW readout set a flag
in the PLL state if the port was at the moment in TBT-alt mode and skip
the verification of PLL parameters in this case.

Fixes: 45fe957 ("drm/i915/display: Add compare config for MTL+ platforms")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11258
Cc: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240626170813.806470-1-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_cx0_phy.c

@@ -3279,6 +3279,10 @@ void intel_cx0pll_readout_hw_state(struct intel_encoder *encoder,
 {
 	pll_state->use_c10 = false;
 
+	pll_state->tbt_mode = intel_tc_port_in_tbt_alt_mode(enc_to_dig_port(encoder));
+	if (pll_state->tbt_mode)
+		return;
+
 	if (intel_encoder_is_c10phy(encoder)) {
 		intel_c10pll_readout_hw_state(encoder, &pll_state->c10);
 		pll_state->use_c10 = true;
@@ -3325,6 +3329,8 @@ static bool mtl_compare_hw_state_c20(const struct intel_c20pll_state *a,
 bool intel_cx0pll_compare_hw_state(const struct intel_cx0pll_state *a,
 				   const struct intel_cx0pll_state *b)
 {
+	if (a->tbt_mode || b->tbt_mode)
+		return true;
 
 	if (a->use_c10 != b->use_c10)
 		return false;
@@ -3420,12 +3426,11 @@ void intel_cx0pll_state_verify(struct intel_atomic_state *state,
 		return;
 
 	encoder = intel_get_crtc_new_encoder(state, new_crtc_state);
+	intel_cx0pll_readout_hw_state(encoder, &mpll_hw_state);
 
-	if (intel_tc_port_in_tbt_alt_mode(enc_to_dig_port(encoder)))
+	if (mpll_hw_state.tbt_mode)
 		return;
 
-	intel_cx0pll_readout_hw_state(encoder, &mpll_hw_state);
-
 	if (intel_encoder_is_c10phy(encoder))
 		intel_c10pll_state_verify(new_crtc_state, crtc, encoder, &mpll_hw_state.c10);
 	else

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

@@ -4027,14 +4027,12 @@ void intel_ddi_get_clock(struct intel_encoder *encoder,
 static void mtl_ddi_get_config(struct intel_encoder *encoder,
 			       struct intel_crtc_state *crtc_state)
 {
-	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
+	intel_cx0pll_readout_hw_state(encoder, &crtc_state->dpll_hw_state.cx0pll);
 
-	if (intel_tc_port_in_tbt_alt_mode(dig_port)) {
+	if (crtc_state->dpll_hw_state.cx0pll.tbt_mode)
 		crtc_state->port_clock = intel_mtl_tbt_calc_port_clock(encoder);
-	} else {
-		intel_cx0pll_readout_hw_state(encoder, &crtc_state->dpll_hw_state.cx0pll);
+	else
 		crtc_state->port_clock = intel_cx0pll_calc_port_clock(encoder, &crtc_state->dpll_hw_state.cx0pll);
-	}
 
 	intel_ddi_get_config(encoder, crtc_state);
 }

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

@@ -265,6 +265,7 @@ struct intel_cx0pll_state {
 	};
 	bool ssc_enabled;
 	bool use_c10;
+	bool tbt_mode;
 };
 
 struct intel_dpll_hw_state {