diff --git a/src/soc/amd/cezanne/acpi/acp.asl b/src/soc/amd/cezanne/acpi/acp.asl
index 806b587f75..51d22183df 100644
--- a/src/soc/amd/cezanne/acpi/acp.asl
+++ b/src/soc/amd/cezanne/acpi/acp.asl
@@ -11,9 +11,6 @@ Scope (\_SB.PCI0.GP41) {
 			Return (STAT)
 		}
 
-		External (\_SB.PCI0.GNB.SMNA, FieldUnitObj)
-		External (\_SB.PCI0.GNB.SMND, FieldUnitObj)
-
 		/* Read SMN register and store value into ACPI variable */
 		Method (SMNR, 1, Serialized)
 		{
diff --git a/src/soc/amd/cezanne/acpi/pci.asl b/src/soc/amd/cezanne/acpi/pci.asl
index 770a8701f6..4942f989e3 100644
--- a/src/soc/amd/cezanne/acpi/pci.asl
+++ b/src/soc/amd/cezanne/acpi/pci.asl
@@ -15,6 +15,26 @@ Device (GNB)
 	{
 		Return (0x0F)
 	}
+
+	/* Add opregion to host bridge needed for ACP driver.
+	 *
+	 * This is used by an ACPI method in the ACP's ACPI code to access different mailbox
+	 * interfaces in the hardware. Some ACP drivers will use that to both notify the PSP
+	 * that the DSP firmware has been loaded, so that the PSP can validate the firmware
+	 * and set the qualifier bit to enable running it, and to configure the ACP's clock
+	 * source.
+	 *
+	 * As this SMN access is not arbitrated and there may be other drivers or parts of
+	 * the firmware attempting to use the SMN access register pair, there is a risk of
+	 * conflict / incorrect data, but given the frequency and duration of accesses, the
+	 * risk is deemed to be quite low.
+	 */
+	OperationRegion (PSMN, PCI_Config, 0x00, 0x100)
+	Field(PSMN, AnyAcc, NoLock, Preserve) {
+		Offset (0xB8),
+		SMNA,   32,
+		SMND,   32,
+	}
 }
 
 /* PCIe GPP */
diff --git a/src/soc/amd/cezanne/root_complex.c b/src/soc/amd/cezanne/root_complex.c
index 81a99e55ec..d9999b9163 100644
--- a/src/soc/amd/cezanne/root_complex.c
+++ b/src/soc/amd/cezanne/root_complex.c
@@ -59,51 +59,6 @@ static void root_complex_fill_ssdt(const struct device *device)
 {
 	if (CONFIG(SOC_AMD_COMMON_BLOCK_ACPI_DPTC))
 		acipgen_dptci();
-
-	/* Add ACPI device, opregion to host bridge needed for ACP driver.
-	 *
-	 * This is used by an ACPI method in the ACP's ACPI code to access different mailbox
-	 * interfaces in th hardware. Some ACP drivers will use that to both notify the PSP
-	 * that the DSP firmware has been loaded, so that the PSP can validate the firmware
-	 * and set the qualifier bit to enable running it, and to configure the ACP's clock
-	 * source.
-	 *
-	 * As this SMN access is not arbitrated and there may be other drivers or parts of
-	 * the firmware attempting to use the SMN access register pair, there is a risk of
-	 * conflict / incorrect data, but given the frequency and duration of accesses, the
-	 * risk is deemed to be quite low.
-	 *
-	 *	Scope (\_SB.PCI0)
-	 *	{
-	 *		Device (GNB)
-	 *		{
-	 *			Name (_ADR, 0x0000000000000000)
-	 *			Method (_STA, 0, NotSerialized)
-	 *			{
-	 *				Return (0x0F)
-	 *			}
-	 *		}
-	 *	}
-	 *	Scope (\_SB.PCI0.GNB)
-	 *	{
-	 *		OperationRegion(SMN, SystemMemory , 0xF80000B8, 0x8)
-	 *		Field(SMN, AnyAcc, NoLock, Preserve) {
-	 *			SMNA,   32,
-	 *			SMND,   32,
-	 *		}
-	 *	}
-	 */
-	acpigen_write_scope(acpi_device_path(device));
-	struct opregion opreg = OPREGION("SMN", SYSTEMMEMORY,
-					 CONFIG_ECAM_MMCONF_BASE_ADDRESS + 0xb8, 0x8);
-	acpigen_write_opregion(&opreg);
-	static const struct fieldlist list[] = {
-		FIELDLIST_NAMESTR("SMNA", 32),
-		FIELDLIST_NAMESTR("SMND", 32),
-	};
-	acpigen_write_field(opreg.name, list, ARRAY_SIZE(list),
-			FIELD_ANYACC | FIELD_NOLOCK | FIELD_PRESERVE);
-	acpigen_write_scope_end();
 }
 
 static const char *gnb_acpi_name(const struct device *dev)