x86: acpi: Split out context creation from base tables

At present acpi_setup_base_tables() both sets up the ACPI context and
writes out the base tables.

We want to use an ACPI writer to write the base tables, so split this
function into two, with acpi_setup_ctx() doing the context set, and
acpi_setup_base_tables() just doing the base tables.

Disable the writer's write_acpi_tables() function for now, to avoid
build errors. It is enabled in a following patch.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/acpi/acpi_writer.c b/lib/acpi/acpi_writer.c
index 5ddffc8..7779bf3 100644
--- a/lib/acpi/acpi_writer.c
+++ b/lib/acpi/acpi_writer.c
@@ -60,23 +60,20 @@
 /*
  * QEMU's version of write_acpi_tables is defined in drivers/misc/qfw.c
  */
-ulong write_acpi_tables(ulong start_addr)
+ulong new_write_acpi_tables(ulong start_addr)
 {
 	struct acpi_ctx *ctx;
 	ulong addr;
-	void *start;
 	int ret;
 
-	ctx = calloc(1, sizeof(*ctx));
+	ctx = malloc(sizeof(*ctx));
 	if (!ctx)
 		return log_msg_ret("mem", -ENOMEM);
-	gd->acpi_ctx = ctx;
-
-	start = map_sysmem(start_addr, 0);
 
 	log_debug("ACPI: Writing ACPI tables at %lx\n", start_addr);
 
 	acpi_reset_items();
+	acpi_setup_ctx(ctx, start_addr);
 
 	ret = acpi_write_all(ctx);
 	if (ret) {
@@ -89,3 +86,16 @@
 
 	return addr;
 }
+
+void acpi_setup_ctx(struct acpi_ctx *ctx, ulong start)
+{
+	gd->acpi_ctx = ctx;
+	memset(ctx, '\0', sizeof(*ctx));
+
+	/* Align ACPI tables to 16-byte boundary */
+	start = ALIGN(start, 16);
+	ctx->base = map_sysmem(start, 0);
+	ctx->current = ctx->base;
+
+	gd_set_acpi_start(start);
+}