firmware: arm_scmi: optee: use optee system invocation

Changes SCMI optee transport to call tee_client_system_session()
to request optee driver to provision an entry context in OP-TEE
for processing OP-TEE messages. This prevents possible deadlock
in case OP-TEE threads are all consumed while these may be waiting
for a clock or regulator to be enable which SCMI OP-TEE service which
requires a free thread context to execute.

Cc: Sudeep Holla <[email protected]>
Cc: Cristian Marussi <[email protected]>
Acked-by: Sudeep Holla <[email protected]>
Reviewed-by: Sumit Garg <[email protected]>
Signed-off-by: Etienne Carriere <[email protected]>
Signed-off-by: Jens Wiklander <[email protected]>

Author: etienne-lms

drivers/firmware/arm_scmi/optee.c

@@ -440,6 +440,10 @@ static int scmi_optee_chan_setup(struct scmi_chan_info *cinfo, struct device *de
 	if (ret)
 		goto err_free_shm;
 
+	ret = tee_client_system_session(scmi_optee_private->tee_ctx, channel->tee_session);
+	if (ret)
+		dev_warn(dev, "Could not switch to system session, do best effort\n");
+
 	ret = get_channel(channel);
 	if (ret)
 		goto err_close_sess;