acpi: Support generation of ACPI code

Add a new file to handle generating ACPI code programatically. This is
used when information must be dynamically added to the tables, e.g. the
SSDT.

Initial support is just for writing simple values. Also add a 'base' value
so that the table can be freed. This likely doesn't happen in normal code,
but is nice to do in tests.

Signed-off-by: Simon Glass <[email protected]>
Reviewed-by: Wolfgang Wallner <[email protected]>
Reviewed-by: Bin Meng <[email protected]>

3 files changed, 41 insertions, 0 deletions

diff --git a/lib/acpi/Makefile b/lib/acpi/Makefile
index caae6c01bd9..85a1f774ad4 100644
--- a/lib/acpi/Makefile
+++ b/lib/acpi/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0+
 #
 
+obj-y += acpigen.o
 obj-y += acpi_device.o
 obj-y += acpi_table.o
diff --git a/lib/acpi/acpi_table.c b/lib/acpi/acpi_table.c
index 431776666e2..acc55e7fad6 100644
--- a/lib/acpi/acpi_table.c
+++ b/lib/acpi/acpi_table.c
@@ -237,6 +237,7 @@ static void acpi_write_xsdt(struct acpi_xsdt *xsdt)
 
 void acpi_setup_base_tables(struct acpi_ctx *ctx, void *start)
 {
+	ctx->base = start;
 	ctx->current = start;
 
 	/* Align ACPI tables to 16 byte */
diff --git a/lib/acpi/acpigen.c b/lib/acpi/acpigen.c
new file mode 100644
index 00000000000..a42ae264943
--- /dev/null
+++ b/lib/acpi/acpigen.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generation of ACPI (Advanced Configuration and Power Interface) tables
+ *
+ * Copyright 2019 Google LLC
+ * Mostly taken from coreboot
+ */
+
+#define LOG_CATEGORY LOGC_ACPI
+
+#include <common.h>
+#include <dm.h>
+#include <acpi/acpigen.h>
+#include <dm/acpi.h>
+
+u8 *acpigen_get_current(struct acpi_ctx *ctx)
+{
+	return ctx->current;
+}
+
+void acpigen_emit_byte(struct acpi_ctx *ctx, uint data)
+{
+	*(u8 *)ctx->current++ = data;
+}
+
+void acpigen_emit_word(struct acpi_ctx *ctx, uint data)
+{
+	acpigen_emit_byte(ctx, data & 0xff);
+	acpigen_emit_byte(ctx, (data >> 8) & 0xff);
+}
+
+void acpigen_emit_dword(struct acpi_ctx *ctx, uint data)
+{
+	/* Output the value in little-endian format */
+	acpigen_emit_byte(ctx, data & 0xff);
+	acpigen_emit_byte(ctx, (data >> 8) & 0xff);
+	acpigen_emit_byte(ctx, (data >> 16) & 0xff);
+	acpigen_emit_byte(ctx, (data >> 24) & 0xff);
+}