firmware: add SCMI agent uclass

This change introduces SCMI agent uclass to interact with a firmware
using the SCMI protocols [1].

SCMI agent uclass currently supports a single method to request
processing of the SCMI message by an identified server. A SCMI message
is made of a byte payload associated to a protocol ID and a message ID,
all defined by the SCMI specification [1]. On return from process_msg()
method, the caller gets the service response.

SCMI agent uclass defines a post bind generic sequence for all devices.
The sequence binds all the SCMI protocols listed in the FDT for that
SCMI agent device. Currently none, but later change will introduce
protocols.

This change implements a simple sandbox device for the SCMI agent uclass.
The sandbox nicely answers SCMI_NOT_SUPPORTED to SCMI messages.
To prepare for further test support, the sandbox exposes a architecture
function for test application to read the sandbox emulated devices state.
Currently supports 2 SCMI agents, identified by an ID in the FDT device
name. The simplistic DM test does nothing yet.

SCMI agent uclass is designed for platforms that embed a SCMI server in
a firmware hosted somewhere, for example in a companion co-processor or
in the secure world of the executing processor. SCMI protocols allow an
SCMI agent to discover and access external resources as clock, reset
controllers and more. SCMI agent and server communicate following the
SCMI specification [1]. This SCMI agent implementation complies with
the DT bindings defined in the Linux kernel source tree regarding
SCMI agent description since v5.8.

Links: [1] https://developer.arm.com/architectures/system-architectures/software-standards/scmi
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

2 files changed, 59 insertions, 0 deletions

diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 2523e59723..4769ec0866 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -366,6 +366,22 @@
 		sandbox_firmware: sandbox-firmware {
 			compatible = "sandbox,firmware";
 		};
+
+		sandbox-scmi-agent@0 {
+			compatible = "sandbox,scmi-agent";
+			#address-cells = <1>;
+			#size-cells = <0>;
+		};
+
+		sandbox-scmi-agent@1 {
+			compatible = "sandbox,scmi-agent";
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			protocol@10 {
+				reg = <0x10>;
+			};
+		};
 	};
 
 	pinctrl-gpio {
diff --git a/arch/sandbox/include/asm/scmi_test.h b/arch/sandbox/include/asm/scmi_test.h
new file mode 100644
index 0000000000..a811fe19c3
--- /dev/null
+++ b/arch/sandbox/include/asm/scmi_test.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020, Linaro Limited
+ */
+
+#ifndef __SANDBOX_SCMI_TEST_H
+#define __SANDBOX_SCMI_TEST_H
+
+struct udevice;
+struct sandbox_scmi_agent;
+struct sandbox_scmi_service;
+
+/**
+ * struct sandbox_scmi_agent - Simulated SCMI service seen by SCMI agent
+ * @idx:	Identifier for the SCMI agent, its index
+ */
+struct sandbox_scmi_agent {
+	uint idx;
+};
+
+/**
+ * struct sandbox_scmi_service - Reference to simutaed SCMI agents/services
+ * @agent:		Pointer to SCMI sandbox agent pointers array
+ * @agent_count:	Number of emulated agents exposed in array @agent.
+ */
+struct sandbox_scmi_service {
+	struct sandbox_scmi_agent **agent;
+	size_t agent_count;
+};
+
+#ifdef CONFIG_SCMI_FIRMWARE
+/**
+ * sandbox_scmi_service_context - Get the simulated SCMI services context
+ * @return:	Reference to backend simulated resources state
+ */
+struct sandbox_scmi_service *sandbox_scmi_service_ctx(void);
+#else
+static inline struct sandbox_scmi_service *sandbox_scmi_service_ctx(void)
+{
+	return NULL;
+}
+#endif /* CONFIG_SCMI_FIRMWARE */
+#endif /* __SANDBOX_SCMI_TEST_H */