coreboot_tables.c: Expose the ACPI RSDP

The ACPI RSDP can only be found in:
- legacy BIOS region
- via UEFI service

On some systems like ARM that legacy BIOS region is not an option, so
to avoid needing UEFI it makes sense to expose the RSDP via a coreboot
table entry.

This also adds the respective unit test.

Change-Id: I591312a2c48f0cbbb03b2787e4b365e9c932afff
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62573
Reviewed-by: Lance Zhao
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/acpi/acpi.c

@@ -1582,6 +1582,13 @@ void preload_acpi_dsdt(void)
 	cbfs_preload(file);
 }
 
+static uintptr_t coreboot_rsdp;
+
+uintptr_t get_coreboot_rsdp(void)
+{
+	return coreboot_rsdp;
+}
+
 unsigned long write_acpi_tables(unsigned long start)
 {
 	unsigned long current;
@@ -1689,6 +1696,7 @@ unsigned long write_acpi_tables(unsigned long start)
 
 	/* We need at least an RSDP and an RSDT Table */
 	rsdp = (acpi_rsdp_t *) current;
+	coreboot_rsdp = (uintptr_t)rsdp;
 	current += sizeof(acpi_rsdp_t);
 	current = acpi_align_current(current);
 	rsdt = (acpi_rsdt_t *) current;

src/commonlib/include/commonlib/coreboot_tables.h

@@ -85,6 +85,7 @@ enum {
 	LB_TAG_BOARD_CONFIG		= 0x0040,
 	LB_TAG_ACPI_CNVS		= 0x0041,
 	LB_TAG_TYPE_C_INFO		= 0x0042,
+	LB_TAG_ACPI_RSDP                = 0x0043,
 	/* The following options are CMOS-related */
 	LB_TAG_CMOS_OPTION_TABLE	= 0x00c8,
 	LB_TAG_OPTION			= 0x00c9,
@@ -574,4 +575,15 @@ struct lb_tpm_physical_presence {
 	uint8_t tpm_version;	/* 1: TPM1.2, 2: TPM2.0 */
 	uint8_t ppi_version;	/* BCD encoded */
 } __packed;
+
+
+/*
+ * Handoff the ACPI RSDP
+ */
+struct lb_acpi_rsdp {
+	uint32_t tag;
+	uint32_t size;
+	struct lb_uint64 rsdp_pointer; /* Address of the ACPI RSDP */
+};
+
 #endif

src/include/acpi/acpi.h

@@ -1220,6 +1220,7 @@ typedef struct acpi_einj {
 } __packed acpi_einj_t;
 
 
+uintptr_t get_coreboot_rsdp(void);
 void acpi_create_einj(acpi_einj_t *einj, uintptr_t addr, u8 actions);
 
 unsigned long fw_cfg_acpi_tables(unsigned long start);

src/lib/coreboot_table.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <acpi/acpi.h>
 #include <arch/cbconfig.h>
 #include <console/console.h>
 #include <console/uart.h>
@@ -420,6 +421,16 @@ static unsigned long lb_table_fini(struct lb_header *head)
 	return (unsigned long)rec + rec->size;
 }
 
+static void lb_add_acpi_rsdp(struct lb_header *head)
+{
+	struct lb_acpi_rsdp *acpi_rsdp;
+	struct lb_record *rec = lb_new_record(head);
+	acpi_rsdp = (struct lb_acpi_rsdp *)rec;
+	acpi_rsdp->tag = LB_TAG_ACPI_RSDP;
+	acpi_rsdp->size = sizeof(*acpi_rsdp);
+	acpi_rsdp->rsdp_pointer = pack_lb64(get_coreboot_rsdp());
+}
+
 size_t write_coreboot_forwarding_table(uintptr_t entry, uintptr_t target)
 {
 	struct lb_header *head;
@@ -523,6 +534,9 @@ static uintptr_t write_coreboot_table(uintptr_t rom_table_end)
 	/* Add all cbmem entries into the coreboot tables. */
 	cbmem_add_records_to_cbtable(head);
 
+	if (CONFIG(HAVE_ACPI_TABLES))
+		lb_add_acpi_rsdp(head);
+
 	/* Remember where my valid memory ranges are */
 	return lb_table_fini(head);
 }

tests/lib/coreboot_table-test.c

@@ -210,6 +210,12 @@ void arch_write_tables(uintptr_t coreboot_table)
 {
 }
 
+static const uintptr_t ebda_base = 0xf0000;
+uintptr_t get_coreboot_rsdp(void)
+{
+	return ebda_base;
+}
+
 struct resource mock_bootmem_ranges[] = {
 	{.base = 0x1000, .size = 0x2000, .flags = LB_MEM_RAM},
 	{.base = 0x0000, .size = 0x4000, .flags = LB_MEM_RAM},
@@ -476,6 +482,12 @@ static void test_write_tables(void **state)
 			assert_int_equal(ram_code(), board_config->ram_code);
 			assert_int_equal(sku_id(), board_config->sku_id);
 			break;
+		case LB_TAG_ACPI_RSDP:
+			assert_int_equal(sizeof(struct lb_acpi_rsdp), record->size);
+
+			const struct lb_acpi_rsdp *acpi_rsdp = (struct lb_acpi_rsdp *)record;
+			assert_int_equal(ebda_base, unpack_lb64(acpi_rsdp->rsdp_pointer));
+			break;
 		default:
 			fail_msg("Unexpected tag found in record. Tag ID: 0x%x", record->tag);
 		}