acpi.c: Swap XSDT and RSDT for adding/finding tables

If ACPI is above 4G it's not possible to have a valid RSDT pointer in
RSDP, therefore swap RSDT and XSDT. Both are always generated on x86.
On other architectures RSDT is often skipped, e.g. aarch64. On top of
that the OS looks at XSDT first. So unconditionally using XSDT and not
RSDT is fine.

This also deal with the ACPI pointer being above 4G. This currently
never happens with x86 platforms.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: I6588676186faa896b6076f871d7f8f633db21e70
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76000
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

1 files changed, 34 insertions, 34 deletions

diff --git a/src/acpi/acpi.c b/src/acpi/acpi.c
index a2e9fdb8d819..07ca408634fd 100644
--- a/src/acpi/acpi.c
+++ b/src/acpi/acpi.c
@@ -49,18 +49,15 @@ void acpi_add_table(acpi_rsdp_t *rsdp, void *table)
 	acpi_rsdt_t *rsdt;
 	acpi_xsdt_t *xsdt = NULL;
 
-	/* The RSDT is mandatory... */
+	/* The 32bit RSDT may not be valid if tables live above 4GiB */
 	rsdt = (acpi_rsdt_t *)(uintptr_t)rsdp->rsdt_address;
-
-	/* ...while the XSDT is not. */
-	if (rsdp->xsdt_address)
-		xsdt = (acpi_xsdt_t *)((uintptr_t)rsdp->xsdt_address);
+	xsdt = (acpi_xsdt_t *)(uintptr_t)rsdp->xsdt_address;
 
 	/* This should always be MAX_ACPI_TABLES. */
-	entries_num = ARRAY_SIZE(rsdt->entry);
+	entries_num = ARRAY_SIZE(xsdt->entry);
 
 	for (i = 0; i < entries_num; i++) {
-		if (rsdt->entry[i] == 0)
+		if (xsdt->entry[i] == 0)
 			break;
 	}
 
@@ -70,36 +67,34 @@ void acpi_add_table(acpi_rsdp_t *rsdp, void *table)
 		return;
 	}
 
-	/* Add table to the RSDT. */
-	rsdt->entry[i] = (uintptr_t)table;
+	/* Add table to the XSDT. */
+	xsdt->entry[i] = (u64)(uintptr_t)table;
 
-	/* Fix RSDT length or the kernel will assume invalid entries. */
-	rsdt->header.length = sizeof(acpi_header_t) + (sizeof(u32) * (i + 1));
+	/* Fix XSDT length or the kernel will assume invalid entries. */
+	xsdt->header.length = sizeof(acpi_header_t) + (sizeof(u64) * (i + 1));
 
 	/* Re-calculate checksum. */
-	rsdt->header.checksum = 0; /* Hope this won't get optimized away */
-	rsdt->header.checksum = acpi_checksum((u8 *)rsdt, rsdt->header.length);
+	xsdt->header.checksum = 0; /* Hope this won't get optimized away */
+	xsdt->header.checksum = acpi_checksum((u8 *)xsdt, xsdt->header.length);
 
 	/*
-	 * And now the same thing for the XSDT. We use the same index as for
+	 * And now the same thing for the RSDT. We use the same index as for
 	 * now we want the XSDT and RSDT to always be in sync in coreboot.
 	 */
-	if (xsdt) {
-		/* Add table to the XSDT. */
-		xsdt->entry[i] = (u64)(uintptr_t)table;
+	if (rsdt && (uintptr_t)table < UINT32_MAX) {
+		/* Add table to the RSDT. */
+		rsdt->entry[i] = (u32)(uintptr_t)table;
 
-		/* Fix XSDT length. */
-		xsdt->header.length = sizeof(acpi_header_t) +
-					(sizeof(u64) * (i + 1));
+		/* Fix RSDT length. */
+		rsdt->header.length = sizeof(acpi_header_t) + (sizeof(u32) * (i + 1));
 
 		/* Re-calculate checksum. */
-		xsdt->header.checksum = 0;
-		xsdt->header.checksum = acpi_checksum((u8 *)xsdt,
-							xsdt->header.length);
+		rsdt->header.checksum = 0;
+		rsdt->header.checksum = acpi_checksum((u8 *)rsdt, rsdt->header.length);
 	}
 
 	printk(BIOS_DEBUG, "ACPI: added table %d/%d, length now %d\n",
-		i + 1, entries_num, rsdt->header.length);
+		i + 1, entries_num, xsdt->header.length);
 }
 
 static enum cb_err acpi_fill_header(acpi_header_t *header, const char name[4],
@@ -1451,14 +1446,19 @@ unsigned long write_acpi_tables(const unsigned long start)
 
 	printk(BIOS_INFO, "ACPI: Writing ACPI tables at %lx.\n", start);
 
-	/* We need at least an RSDP and an RSDT Table */
+	/* We need at least an RSDP, RSDT for ACPI 1.0 compat, otherwise XSDT */
 	rsdp = (acpi_rsdp_t *)current;
 	coreboot_rsdp = (uintptr_t)rsdp;
 	current += sizeof(acpi_rsdp_t);
 	current = acpi_align_current(current);
-	rsdt = (acpi_rsdt_t *)current;
-	current += sizeof(acpi_rsdt_t);
-	current = acpi_align_current(current);
+	if (current + sizeof(acpi_rsdt_t) - 1 <= UINT32_MAX) {
+		rsdt = (acpi_rsdt_t *)current;
+		current += sizeof(acpi_rsdt_t);
+		current = acpi_align_current(current);
+	} else {
+		printk(BIOS_INFO, "Not adding RSDT because tables reside above 4G.");
+	}
+
 	xsdt = (acpi_xsdt_t *)current;
 	current += sizeof(acpi_xsdt_t);
 	current = acpi_align_current(current);
@@ -1554,7 +1554,7 @@ static acpi_rsdp_t *valid_rsdp(acpi_rsdp_t *rsdp)
 void *acpi_find_wakeup_vector(void)
 {
 	char *p, *end;
-	acpi_rsdt_t *rsdt;
+	acpi_xsdt_t *xsdt;
 	acpi_facs_t *facs;
 	acpi_fadt_t *fadt = NULL;
 	acpi_rsdp_t *rsdp = NULL;
@@ -1580,13 +1580,13 @@ void *acpi_find_wakeup_vector(void)
 	}
 
 	printk(BIOS_DEBUG, "RSDP found at %p\n", rsdp);
-	rsdt = (acpi_rsdt_t *)(uintptr_t)rsdp->rsdt_address;
+	xsdt = (acpi_xsdt_t *)(uintptr_t)rsdp->xsdt_address;
 
-	end = (char *)rsdt + rsdt->header.length;
-	printk(BIOS_DEBUG, "RSDT found at %p ends at %p\n", rsdt, end);
+	end = (char *)xsdt + xsdt->header.length;
+	printk(BIOS_DEBUG, "XSDT found at %p ends at %p\n", xsdt, end);
 
-	for (i = 0; ((char *)&rsdt->entry[i]) < end; i++) {
-		fadt = (acpi_fadt_t *)(uintptr_t)rsdt->entry[i];
+	for (i = 0; ((char *)&xsdt->entry[i]) < end; i++) {
+		fadt = (acpi_fadt_t *)(uintptr_t)xsdt->entry[i];
 		if (strncmp((char *)fadt, "FACP", 4) == 0)
 			break;
 		fadt = NULL;