acpi: Add helper for deactivating memory region

Sometimes memory resource may be overlapping with
SystemMemory Operation Region by design, for example if the
memory region is used as a mailbox for communication with a
firmware in the system. One occasion of such mailboxes is
USB Type-C Connector System Software Interface (UCSI).

With regions like that, it is important that the driver is
able to map the memory with the requirements it has. For
example, the driver should be allowed to map the memory as
non-cached memory. However, if the operation region has been
accessed before the driver has mapped the memory, the memory
has been marked as write-back by the time the driver is
loaded. That means the driver will fail to map the memory
if it expects non-cached memory.

To work around the problem, introducing helper that the
drivers can use to temporarily deactivate (unmap)
SystemMemory Operation Regions that overlap with their
IO memory.

Fixes: 8243edf44152 ("usb: typec: ucsi: Add ACPI driver")
Cc: stable@vger.kernel.org
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 4b35a66383f9..e54f40974eb0 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -443,6 +443,9 @@ int acpi_check_resource_conflict(const struct resource *res);
 int acpi_check_region(resource_size_t start, resource_size_t n,
 		      const char *name);
 
+acpi_status acpi_release_memory(acpi_handle handle, struct resource *res,
+				u32 level);
+
 int acpi_resources_are_enforced(void);
 
 #ifdef CONFIG_HIBERNATION