x86/acpi: Add VFCT table

Add VFCT table to provide PCI Optiom Rom for
AMD graphic devices.
Useful for GNU Linux payloads and embedded dual GPU systems.

Tested on Lenovo T500 with AMD RV635 as secondary gpu.

Original Change-Id: I3b4a587c71e7165338cad3aca77ed5afa085a63c
Signed-off-by: Patrick Rudolph <siro@das-labor.org>

Change-Id: I4dc00005270240c048272b2e4f52ae46ba1c9422
Reviewed-on: https://review.coreboot.org/18192
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/arch/x86/acpi.c b/src/arch/x86/acpi.c
index 53c4135..703bfa1 100644
--- a/src/arch/x86/acpi.c
+++ b/src/arch/x86/acpi.c
@@ -589,6 +589,31 @@
 	header->checksum = acpi_checksum((void *)hpet, sizeof(acpi_hpet_t));
 }
 
+void acpi_create_vfct(struct device *device,
+		      struct acpi_vfct *vfct,
+		      unsigned long (*acpi_fill_vfct)(struct device *device, struct acpi_vfct *vfct_struct, unsigned long current))
+{
+	acpi_header_t *header = &(vfct->header);
+	unsigned long current = (unsigned long)vfct + sizeof(struct acpi_vfct);
+
+	memset((void *)vfct, 0, sizeof(struct acpi_vfct));
+
+	/* Fill out header fields. */
+	memcpy(header->signature, "VFCT", 4);
+	memcpy(header->oem_id, OEM_ID, 6);
+	memcpy(header->oem_table_id, ACPI_TABLE_CREATOR, 8);
+	memcpy(header->asl_compiler_id, ASLC, 4);
+
+	header->length = sizeof(struct acpi_vfct);
+	header->revision = 1; /* ACPI 1.0: N/A, ACPI 2.0/3.0/4.0: 1 */
+
+	current = acpi_fill_vfct(device, vfct, current);
+
+	/* (Re)calculate length and checksum. */
+	header->length = current - (unsigned long)vfct;
+	header->checksum = acpi_checksum((void *)vfct, header->length);
+}
+
 void acpi_create_ivrs(acpi_ivrs_t *ivrs,
 		      unsigned long (*acpi_fill_ivrs)(acpi_ivrs_t* ivrs_struct, unsigned long current))
 {