ACPI: PRM: Add PRM handler direct call support

Platform Runtime Mechanism (PRM) handlers can be invoked from either the AML
interpreter or directly by an OS driver. Implement the latter.

  [ bp: Massage commit message. ]

Signed-off-by: John Allen <john.allen@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20240730151731.15363-2-john.allen@amd.com

Author: jallen-amd

drivers/acpi/prmt.c

@@ -214,6 +214,30 @@ static struct prm_handler_info *find_prm_handler(const guid_t *guid)
 #define UPDATE_LOCK_ALREADY_HELD 	4
 #define UPDATE_UNLOCK_WITHOUT_LOCK 	5
 
+int acpi_call_prm_handler(guid_t handler_guid, void *param_buffer)
+{
+	struct prm_handler_info *handler = find_prm_handler(&handler_guid);
+	struct prm_module_info *module = find_prm_module(&handler_guid);
+	struct prm_context_buffer context;
+	efi_status_t status;
+
+	if (!module || !handler)
+		return -ENODEV;
+
+	memset(&context, 0, sizeof(context));
+	ACPI_COPY_NAMESEG(context.signature, "PRMC");
+	context.identifier         = handler->guid;
+	context.static_data_buffer = handler->static_data_buffer_addr;
+	context.mmio_ranges        = module->mmio_info;
+
+	status = efi_call_acpi_prm_handler(handler->handler_addr,
+					   (u64)param_buffer,
+					   &context);
+
+	return efi_status_to_err(status);
+}
+EXPORT_SYMBOL_GPL(acpi_call_prm_handler);
+
 /*
  * This is the PlatformRtMechanism opregion space handler.
  * @function: indicates the read/write. In fact as the PlatformRtMechanism

include/linux/prmt.h

@@ -2,6 +2,11 @@
 
 #ifdef CONFIG_ACPI_PRMT
 void init_prmt(void);
+int acpi_call_prm_handler(guid_t handler_guid, void *param_buffer);
 #else
 static inline void init_prmt(void) { }
+static inline int acpi_call_prm_handler(guid_t handler_guid, void *param_buffer)
+{
+	return -EOPNOTSUPP;
+}
 #endif