[PATCH v5 13/36] acpi_table: Support platforms with unusable RSDT

[Patrick Rudolph <patrick.rudolph@9elements.com>]

Since ACPI 2.0 the RSDT is deprecated and the XSDT should be preferred.
Until now the RSDT and XSDT entries were keept in sync as all platforms
that installed ACPI tables placed them below 4GiB and thus the address
would fit into the 32bit RSDT.

On platforms that do not have usable DRAM below 4GiB, like QEMU sbsa,
the RSDT cannot be used. Allow both RSDT and XSDT to be null and only
fill those tables that are present in acpi_add_table().

TEST: Fixes a crash on QEMU sbsa and allows to boot on QEMU sbsa.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
---
Changelog v4:
- Updated commit message and better explain why this change is needed

---
 lib/acpi/acpi_table.c | 95 ++++++++++++++++++++++++++-----------------
 1 file changed, 57 insertions(+), 38 deletions(-)

diff --git a/lib/acpi/acpi_table.c b/lib/acpi/acpi_table.c
index 9d9c8befe8..d6357bdc4d 100644
--- a/lib/acpi/acpi_table.c
+++ b/lib/acpi/acpi_table.c
@@ -157,51 +157,70 @@ int acpi_add_table(struct acpi_ctx *ctx, void *table)
 	struct acpi_rsdt *rsdt;
 	struct acpi_xsdt *xsdt;
 
-	/* The RSDT is mandatory while the XSDT is not */
-	rsdt = ctx->rsdt;
-
-	/* This should always be MAX_ACPI_TABLES */
-	entries_num = ARRAY_SIZE(rsdt->entry);
-
-	for (i = 0; i < entries_num; i++) {
-		if (rsdt->entry[i] == 0)
-			break;
-	}
-
-	if (i >= entries_num) {
-		log_err("ACPI: Error: too many tables\n");
-		return -E2BIG;
-	}
+	/* On legacy x86 platforms the RSDT is mandatory while the XSDT is not.
+	 * On other platforms there might be no memory below 4GiB, thus RSDT is NULL.
+	 */
+	if (ctx->rsdt) {
+		rsdt = ctx->rsdt;
 
-	/* Add table to the RSDT */
-	rsdt->entry[i] = nomap_to_sysmem(table);
+		/* This should always be MAX_ACPI_TABLES */
+		entries_num = ARRAY_SIZE(rsdt->entry);
 
-	/* Fix RSDT length or the kernel will assume invalid entries */
-	rsdt->header.length = sizeof(struct acpi_table_header) +
-				(sizeof(u32) * (i + 1));
+		for (i = 0; i < entries_num; i++) {
+			if (rsdt->entry[i] == 0)
+				break;
+		}
 
-	/* Re-calculate checksum */
-	rsdt->header.checksum = 0;
-	rsdt->header.checksum = table_compute_checksum((u8 *)rsdt,
-						       rsdt->header.length);
+		if (i >= entries_num) {
+			log_err("ACPI: Error: too many tables\n");
+			return -E2BIG;
+		}
 
-	/*
-	 * And now the same thing for the XSDT. We use the same index as for
-	 * now we want the XSDT and RSDT to always be in sync in U-Boot
-	 */
-	xsdt = ctx->xsdt;
+		/* Add table to the RSDT */
+		rsdt->entry[i] = nomap_to_sysmem(table);
 
-	/* Add table to the XSDT */
-	xsdt->entry[i] = nomap_to_sysmem(table);
+		/* Fix RSDT length or the kernel will assume invalid entries */
+		rsdt->header.length = sizeof(struct acpi_table_header) +
+					(sizeof(u32) * (i + 1));
 
-	/* Fix XSDT length */
-	xsdt->header.length = sizeof(struct acpi_table_header) +
-				(sizeof(u64) * (i + 1));
+		/* Re-calculate checksum */
+		rsdt->header.checksum = 0;
+		rsdt->header.checksum = table_compute_checksum((u8 *)rsdt,
+							       rsdt->header.length);
+	}
 
-	/* Re-calculate checksum */
-	xsdt->header.checksum = 0;
-	xsdt->header.checksum = table_compute_checksum((u8 *)xsdt,
-						       xsdt->header.length);
+	if (ctx->xsdt) {
+		/*
+		 * And now the same thing for the XSDT. We use the same index as for
+		 * now we want the XSDT and RSDT to always be in sync in U-Boot
+		 */
+		xsdt = ctx->xsdt;
+
+		/* This should always be MAX_ACPI_TABLES */
+		entries_num = ARRAY_SIZE(xsdt->entry);
+
+		for (i = 0; i < entries_num; i++) {
+			if (xsdt->entry[i] == 0)
+				break;
+		}
+
+		if (i >= entries_num) {
+			log_err("ACPI: Error: too many tables\n");
+			return -E2BIG;
+		}
+
+		/* Add table to the XSDT */
+		xsdt->entry[i] = nomap_to_sysmem(table);
+
+		/* Fix XSDT length */
+		xsdt->header.length = sizeof(struct acpi_table_header) +
+					(sizeof(u64) * (i + 1));
+
+		/* Re-calculate checksum */
+		xsdt->header.checksum = 0;
+		xsdt->header.checksum = table_compute_checksum((u8 *)xsdt,
+							       xsdt->header.length);
+	}
 
 	return 0;
 }
-- 
2.46.0