x86: Move base tables to a writer function

Use the new ACPI writer to write the base tables at the start of the area,
moving this code from the x86 implementation.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/acpi/base.c b/lib/acpi/base.c
new file mode 100644
index 0000000..3e8d703
--- /dev/null
+++ b/lib/acpi/base.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Write base ACPI tables
+ *
+ * Copyright 2021 Google LLC
+ */
+
+#include <common.h>
+#include <acpi/acpi_table.h>
+#include <dm/acpi.h>
+#include <mapmem.h>
+#include <tables_csum.h>
+
+void acpi_write_rsdp(struct acpi_rsdp *rsdp, struct acpi_rsdt *rsdt,
+		     struct acpi_xsdt *xsdt)
+{
+	memset(rsdp, 0, sizeof(struct acpi_rsdp));
+
+	memcpy(rsdp->signature, RSDP_SIG, 8);
+	memcpy(rsdp->oem_id, OEM_ID, 6);
+
+	rsdp->length = sizeof(struct acpi_rsdp);
+	rsdp->rsdt_address = map_to_sysmem(rsdt);
+
+	rsdp->xsdt_address = map_to_sysmem(xsdt);
+	rsdp->revision = ACPI_RSDP_REV_ACPI_2_0;
+
+	/* Calculate checksums */
+	rsdp->checksum = table_compute_checksum(rsdp, 20);
+	rsdp->ext_checksum = table_compute_checksum(rsdp,
+						    sizeof(struct acpi_rsdp));
+}
+
+static void acpi_write_rsdt(struct acpi_rsdt *rsdt)
+{
+	struct acpi_table_header *header = &rsdt->header;
+
+	/* Fill out header fields */
+	acpi_fill_header(header, "RSDT");
+	header->length = sizeof(struct acpi_rsdt);
+	header->revision = 1;
+
+	/* Entries are filled in later, we come with an empty set */
+
+	/* Fix checksum */
+	header->checksum = table_compute_checksum(rsdt,
+						  sizeof(struct acpi_rsdt));
+}
+
+static void acpi_write_xsdt(struct acpi_xsdt *xsdt)
+{
+	struct acpi_table_header *header = &xsdt->header;
+
+	/* Fill out header fields */
+	acpi_fill_header(header, "XSDT");
+	header->length = sizeof(struct acpi_xsdt);
+	header->revision = 1;
+
+	/* Entries are filled in later, we come with an empty set */
+
+	/* Fix checksum */
+	header->checksum = table_compute_checksum(xsdt,
+						  sizeof(struct acpi_xsdt));
+}
+
+static int acpi_write_base(struct acpi_ctx *ctx,
+			   const struct acpi_writer *entry)
+{
+	/* We need at least an RSDP and an RSDT Table */
+	ctx->rsdp = ctx->current;
+	acpi_inc_align(ctx, sizeof(struct acpi_rsdp));
+	ctx->rsdt = ctx->current;
+	acpi_inc_align(ctx, sizeof(struct acpi_rsdt));
+	ctx->xsdt = ctx->current;
+	acpi_inc_align(ctx, sizeof(struct acpi_xsdt));
+
+	/* clear all table memory */
+	memset(ctx->base, '\0', ctx->current - ctx->base);
+
+	acpi_write_rsdp(ctx->rsdp, ctx->rsdt, ctx->xsdt);
+	acpi_write_rsdt(ctx->rsdt);
+	acpi_write_xsdt(ctx->xsdt);
+
+	return 0;
+}
+/*
+ * Per ACPI spec, the FACS table address must be aligned to a 64-byte boundary
+ * (Windows checks this, but Linux does not).
+ *
+ * Use the '0' prefix to put this one first
+ */
+ACPI_WRITER(0base, NULL, acpi_write_base, ACPIWF_ALIGN64);