acpi: Move the table-finding functions into the libary

This is useful for other features. Move the function into library code
so it can be used outside just the 'acpi' command.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>

2 files changed, 47 insertions, 0 deletions

diff --git a/lib/acpi/Makefile b/lib/acpi/Makefile
index 12337abaecf..c1c9675b5d2 100644
--- a/lib/acpi/Makefile
+++ b/lib/acpi/Makefile
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0+
 #
 
+obj-y += acpi.o
+
 ifdef CONFIG_$(SPL_TPL_)GENERATE_ACPI_TABLE
 
 obj-$(CONFIG_$(SPL_)ACPIGEN) += acpigen.o
diff --git a/lib/acpi/acpi.c b/lib/acpi/acpi.c
new file mode 100644
index 00000000000..14b15754f49
--- /dev/null
+++ b/lib/acpi/acpi.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Utility functions for ACPI
+ *
+ * Copyright 2023 Google LLC
+ */
+
+#include <common.h>
+#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;
+	int len, i, count;
+
+	rsdp = map_sysmem(gd_acpi_start(), 0);
+	if (!rsdp)
+		return NULL;
+	rsdt = map_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;
+
+		hdr = map_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) && fadt->dsdt)
+				return map_sysmem(fadt->dsdt, 0);
+			if (!memcmp(sig, "FACS", ACPI_NAME_LEN) &&
+			    fadt->firmware_ctrl)
+				return map_sysmem(fadt->firmware_ctrl, 0);
+		}
+	}
+
+	return NULL;
+}