soc/amd: introduce common SMU S3/4/5 entry message code

The smu_sx_entry function is identical for all AMD SoCs, so introduce it
as common code that can be selected to be included in the build via the
SOC_AMD_COMMON_BLOCK_SMU_SX_ENTRY Kconfig option. The only SoC-specific
difference in this function is the ID of the SMC_MSG_S3ENTRY message
which is defined in each SoC's soc/smu.h include file.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Suggested-by: Elyes Haouas <ehaouas@noos.fr>
Change-Id: I49758e9333a351d8e50e8f1b53a7f00fbe89866c
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71875
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>

src/soc/amd/common/block/smu/Kconfig

@@ -3,3 +3,10 @@ config SOC_AMD_COMMON_BLOCK_SMU
 	select SOC_AMD_COMMON_BLOCK_SMN
 	help
 	  Select this option to add functions to communicate with the SMU to the build.
+
+config SOC_AMD_COMMON_BLOCK_SMU_SX_ENTRY
+	bool
+	depends on SOC_AMD_COMMON_BLOCK_SMU
+	help
+	  Select this option to add the function to send the S3/4/5 entry
+	  message to the SMU.

src/soc/amd/common/block/smu/Makefile.inc

@@ -3,3 +3,5 @@ smm-$(CONFIG_SOC_AMD_COMMON_BLOCK_SMU) += smu.c
 bootblock-$(CONFIG_SOC_AMD_COMMON_BLOCK_SMU) += smu.c
 romstage-$(CONFIG_SOC_AMD_COMMON_BLOCK_SMU) += smu.c
 ramstage-$(CONFIG_SOC_AMD_COMMON_BLOCK_SMU) += smu.c
+
+smm-$(CONFIG_SOC_AMD_COMMON_BLOCK_SMU_SX_ENTRY) += smu_sx_entry.c

src/soc/amd/common/block/smu/smu_sx_entry.c

@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <console/console.h>
+#include <amdblocks/smu.h>
+#include <soc/smu.h>
+
+/*
+ * Request the SMU to put system into S3, S4, or S5. On entry, SlpTyp determines S-State and
+ * SlpTypeEn gets set by the SMU. Function does not return if successful.
+ */
+void smu_sx_entry(void)
+{
+	struct smu_payload msg = { 0 }; /* Unused for SMC_MSG_S3ENTRY */
+
+	printk(BIOS_DEBUG, "SMU: Put system into S3/S4/S5\n");
+	send_smu_message(SMC_MSG_S3ENTRY, &msg);
+}