1 files changed, 75 insertions, 0 deletions
diff --git a/lib/acpi/acpi.c b/lib/acpi/acpi.c
new file mode 100644
index 00000000000..f4d5c1e25d0
--- /dev/null
+++ b/lib/acpi/acpi.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Utility functions for ACPI
+ *
+ * Copyright 2023 Google LLC
+ */
+
+#include <mapmem.h>
+#include <acpi/acpi_table.h>
+#include <asm/global_data.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct acpi_table_header *acpi_find_table(const char *sig)
+{
+	struct acpi_rsdp *rsdp;
+	struct acpi_rsdt *rsdt;
+	struct acpi_xsdt *xsdt;
+	int len, i, count;
+
+	rsdp = map_sysmem(gd_acpi_start(), 0);
+	if (!rsdp)
+		return NULL;
+	if (rsdp->xsdt_address) {
+		xsdt = nomap_sysmem(rsdp->xsdt_address, 0);
+		len = xsdt->header.length - sizeof(xsdt->header);
+		count = len / sizeof(u64);
+	} else {
+		if (!rsdp->rsdt_address)
+			return NULL;
+		rsdt = nomap_sysmem(rsdp->rsdt_address, 0);
+		len = rsdt->header.length - sizeof(rsdt->header);
+		count = len / sizeof(u32);
+	}
+	for (i = 0; i < count; i++) {
+		struct acpi_table_header *hdr;
+
+		if (rsdp->xsdt_address)
+			hdr = nomap_sysmem(xsdt->entry[i], 0);
+		else
+			hdr = nomap_sysmem(rsdt->entry[i], 0);
+		if (!memcmp(hdr->signature, sig, ACPI_NAME_LEN))
+			return hdr;
+		if (!memcmp(hdr->signature, "FACP", ACPI_NAME_LEN)) {
+			struct acpi_fadt *fadt = (struct acpi_fadt *)hdr;
+
+			if (!memcmp(sig, "DSDT", ACPI_NAME_LEN)) {
+				void *dsdt;
+
+				if (fadt->header.revision >= 3 && fadt->x_dsdt)
+					dsdt = nomap_sysmem(fadt->x_dsdt, 0);
+				else if (fadt->dsdt)
+					dsdt = nomap_sysmem(fadt->dsdt, 0);
+				else
+					dsdt = NULL;
+				return dsdt;
+			}
+
+			if (!memcmp(sig, "FACS", ACPI_NAME_LEN)) {
+				void *facs;
+
+				if (fadt->header.revision >= 3 &&
+				    fadt->x_firmware_ctrl)
+					facs = nomap_sysmem(fadt->x_firmware_ctrl, 0);
+				else if (fadt->firmware_ctrl)
+					facs = nomap_sysmem(fadt->firmware_ctrl, 0);
+				else
+					facs = NULL;
+				return facs;
+			}
+		}
+	}
+
+	return NULL;
+}