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: 8243edf441 ("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>

drivers/acpi/osl.c

@@ -45,6 +45,8 @@
 #include <linux/uaccess.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 
+#include "acpica/accommon.h"
+#include "acpica/acnamesp.h"
 #include "internal.h"
 
 #define _COMPONENT		ACPI_OS_SERVICES
@@ -1490,6 +1492,76 @@ int acpi_check_region(resource_size_t start, resource_size_t n,
 }
 EXPORT_SYMBOL(acpi_check_region);
 
+static acpi_status acpi_deactivate_mem_region(acpi_handle handle, u32 level,
+					      void *_res, void **return_value)
+{
+	struct acpi_mem_space_context **mem_ctx;
+	union acpi_operand_object *handler_obj;
+	union acpi_operand_object *region_obj2;
+	union acpi_operand_object *region_obj;
+	struct resource *res = _res;
+	acpi_status status;
+
+	region_obj = acpi_ns_get_attached_object(handle);
+	if (!region_obj)
+		return AE_OK;
+
+	handler_obj = region_obj->region.handler;
+	if (!handler_obj)
+		return AE_OK;
+
+	if (region_obj->region.space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		return AE_OK;
+
+	if (!(region_obj->region.flags & AOPOBJ_SETUP_COMPLETE))
+		return AE_OK;
+
+	region_obj2 = acpi_ns_get_secondary_object(region_obj);
+	if (!region_obj2)
+		return AE_OK;
+
+	mem_ctx = (void *)&region_obj2->extra.region_context;
+
+	if (!(mem_ctx[0]->address >= res->start &&
+	      mem_ctx[0]->address < res->end))
+		return AE_OK;
+
+	status = handler_obj->address_space.setup(region_obj,
+						  ACPI_REGION_DEACTIVATE,
+						  NULL, (void **)mem_ctx);
+	if (ACPI_SUCCESS(status))
+		region_obj->region.flags &= ~(AOPOBJ_SETUP_COMPLETE);
+
+	return status;
+}
+
+/**
+ * acpi_release_memory - Release any mappings done to a memory region
+ * @handle: Handle to namespace node
+ * @res: Memory resource
+ * @level: A level that terminates the search
+ *
+ * Walks through @handle and unmaps all SystemMemory Operation Regions that
+ * overlap with @res and that have already been activated (mapped).
+ *
+ * This is a helper that allows drivers to place special requirements on memory
+ * region that may overlap with operation regions, primarily allowing them to
+ * safely map the region as non-cached memory.
+ *
+ * The unmapped Operation Regions will be automatically remapped next time they
+ * are called, so the drivers do not need to do anything else.
+ */
+acpi_status acpi_release_memory(acpi_handle handle, struct resource *res,
+				u32 level)
+{
+	if (!(res->flags & IORESOURCE_MEM))
+		return AE_TYPE;
+
+	return acpi_walk_namespace(ACPI_TYPE_REGION, handle, level,
+				   acpi_deactivate_mem_region, NULL, res, NULL);
+}
+EXPORT_SYMBOL_GPL(acpi_release_memory);
+
 /*
  * Let drivers know whether the resource checks are effective
  */

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