drivers/smmstore: Implement SMMSTORE version 2

SMMSTORE version 2 is a complete redesign of the current driver. It is
not backwards-compatible with version 1, and only one version can be
used at a time.

Key features:
* Uses a fixed communication buffer instead of writing to arbitrary
  memory addresses provided by untrusted ring0 code.
* Gives the caller full control over the used data format.
* Splits the store into smaller chunks to allow fault tolerant updates.
* Doesn't provide feedback about the actual read/written bytes, just
  returns error or success in registers.
* Returns an error if the requested operation would overflow the
  communication buffer.

Separate the SMMSTORE into 64 KiB blocks that can individually be
read/written/erased. To be used by payloads that implement a
FaultTolerant Variable store like TianoCore.

The implementation has been tested against EDK2 master.

An example EDK2 implementation can be found here:
eb1127744a

Change-Id: I25e49d184135710f3e6dd1ad3bed95de950fe057
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Christian Walter <christian.walter@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40520
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Michał Żygowski <michal.zygowski@3mdeb.com>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>

src/commonlib/include/commonlib/cbmem_id.h

@@ -68,6 +68,7 @@
 #define CBMEM_ID_ROM3		0x524f4d33
 #define CBMEM_ID_FMAP		0x464d4150
 #define CBMEM_ID_FSP_LOGO	0x4c4f474f
+#define CBMEM_ID_SMM_COMBUFFER	0x53534d32
 
 #define CBMEM_ID_TO_NAME_TABLE				 \
 	{ CBMEM_ID_ACPI,		"ACPI       " }, \

src/commonlib/include/commonlib/coreboot_tables.h

@@ -80,6 +80,7 @@ enum {
 	LB_TAG_TCPA_LOG			= 0x0036,
 	LB_TAG_FMAP			= 0x0037,
 	LB_TAG_PLATFORM_BLOB_VERSION	= 0x0038,
+	LB_TAG_SMMSTOREV2		= 0x0039,
 	LB_TAG_CMOS_OPTION_TABLE	= 0x00c8,
 	LB_TAG_OPTION			= 0x00c9,
 	LB_TAG_OPTION_ENUM		= 0x00ca,
@@ -484,4 +485,20 @@ struct	cmos_checksum {
 #define CHECKSUM_PCBIOS	1
 };
 
+/* SMMSTOREv2 record
+ * This record contains information to use SMMSTOREv2.
+ */
+
+struct lb_smmstorev2 {
+	uint32_t tag;
+	uint32_t size;
+	uint32_t num_blocks;		/* Number of writeable blocks in SMM */
+	uint32_t block_size;		/* Size of a block in byte. Default: 64 KiB */
+	uint32_t mmap_addr;		/* MMIO address of the store for read only access */
+	uint32_t com_buffer;		/* Physical address of the communication buffer */
+	uint32_t com_buffer_size;	/* Size of the communication buffer in bytes */
+	uint8_t apm_cmd;		/* The command byte to write to the APM I/O port */
+	uint8_t unused[3];		/* Set to zero */
+};
+
 #endif