firmware: arm_scmi: new optee transport layer

Add a new transport channel to the SCMI firmware interface driver for
SCMI message exchange based on OP-TEE transport channel that leverage
OP-TEE secure threaded context for processing of SCMI messages.

The current proposal uses a statically defined physical memory area
to be used as shared memory SCMI endpoints. The location is extracted
from the FDT upon property "shmem".

Entry in OP-TEE threaded context is realized by invoking a service
PTA (Pseudo TA) in OP-TEE OS. Each invocation carries a agent
numerical identifier for which a message is pending in the shared
memory. The OP-TEE service provides means to get the agent identifier
value for a given shared memory location.

OPTEE transport driver depends on CONFIG_OPTEE and probes from SCMI
compatible identifier "arm,scmi-optee".

Change-Id: Iedae882abfbbd5d1b6706ea0502fc867fce6cee0
Signed-off-by: Etienne Carriere <[email protected]>

Author: etienne-lms

drivers/firmware/Kconfig

@@ -11,7 +11,7 @@ source "drivers/firmware/arm_scmi/Kconfig"
 config ARM_SCPI_PROTOCOL
 	tristate "ARM System Control and Power Interface (SCPI) Message Protocol"
 	depends on ARM || ARM64 || COMPILE_TEST
-	depends on MAILBOX
+	depends on MAILBOX || HAVE_ARM_SMCCC || OPTEE
 	help
 	  System Control and Power Interface (SCPI) Message Protocol is
 	  defined for the purpose of communication between the Application

drivers/firmware/arm_scmi/Makefile

@@ -6,6 +6,7 @@ scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_MAILBOX) += mailbox.o
 scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_SMC) += smc.o
 scmi-transport-$(CONFIG_ARM_SCMI_HAVE_MSG) += msg.o
 scmi-transport-$(CONFIG_ARM_SCMI_TRANSPORT_VIRTIO) += virtio.o
+scmi-transport-$(CONFIG_OPTEE) += optee.o
 scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o
 scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
 		    $(scmi-transport-y)

drivers/firmware/arm_scmi/common.h

@@ -421,6 +421,9 @@ extern const struct scmi_desc scmi_smc_desc;
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
 extern const struct scmi_desc scmi_virtio_desc;
 #endif
+#ifdef CONFIG_OPTEE
+extern const struct scmi_desc scmi_optee_desc;
+#endif
 
 void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr, void *priv);
 void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id);

drivers/firmware/arm_scmi/driver.c

@@ -1997,6 +1997,9 @@ static const struct of_device_id scmi_of_match[] = {
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC
 	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
 #endif
+#ifdef CONFIG_OPTEE
+	{ .compatible = "linaro,scmi-optee", .data = &scmi_optee_desc },
+#endif
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_VIRTIO
 	{ .compatible = "arm,scmi-virtio", .data = &scmi_virtio_desc},
 #endif