The ACPI specification says that we should use the 64-bit address offsets
contained within the FADT if they exist. However, Windows uses the legacy
address. Various vendors have left incorrect values in the 64-bit field
which then causes problems later. Since the vast majority of machines have
never been tested with an OS that uses the 64-bit value by default, we should
behave like Windows and ignore the spec by only using the 64-bit address if
it contains something that can't be represented in the legacy field. Since
system io space is only 16 bits on x86, this should be entirely safe.
Signed-off-by: Matthew Garrett <mjg@xxxxxxxxxx>
---
Len, this is a clear case of the spec not matching real-life behaviour.
I'd be amazed if anyone can find an x86 system that uses system-io space
for these values and doesn't contain an accurate value in the 32-bit
field. On the other hand, we've seen machines that assume the
Windows-style behaviour and we keep finding more. A blacklist isn't the
correct solution for this problem.
diff --git a/drivers/acpi/tables/tbfadt.c b/drivers/acpi/tables/tbfadt.c
index 2817158..89a3c82 100644
--- a/drivers/acpi/tables/tbfadt.c
+++ b/drivers/acpi/tables/tbfadt.c
@@ -320,9 +320,30 @@ static void acpi_tb_convert_fadt(void)
ACPI_ADD_PTR(struct acpi_generic_address, &acpi_gbl_FADT,
fadt_info_table[i].target);
- /* Expand only if the X target is null */
-
- if (!target->address) {
+ /*
+ * The ACPI specification says that we should use the
+ * 64-bit address offsets if they exists. However,
+ * Windows uses the legacy address. Various vendors
+ * have left incorrect values in the 64-bit field,
+ * which then causes problems later. Since the vast
+ * majority of machines have never been tested with an
+ * OS that uses the 64-bit value by default, we should
+ * behave like Windows and ignore the spec by only
+ * using the 64-bit address if it contains something
+ * that can't be represented in the legacy
+ * field. Since system io space is only 16 bits on
+ * x86, this should be entirely safe. We also extend
+ * the 32-bit value into the 64-bit one if no 64-bit
+ * address is provided.
+ */
+
+ if (!target->address
+#ifdef CONFIG_X86
+ || (target->space_id == ACPI_ADR_SPACE_SYSTEM_IO &&
+ *ACPI_ADD_PTR(u32, &acpi_gbl_FADT,
+ fadt_info_table[i].source))
+#endif
+ ) {
acpi_tb_init_generic_address(target,
*ACPI_ADD_PTR(u8,
&acpi_gbl_FADT,
--
Matthew Garrett | mjg59@xxxxxxxxxxxxx
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