firmware: arm_scmi: add basic driver infrastructure for SCMI

The SCMI is intended to allow OSPM to manage various functions that are
provided by the hardware platform it is running on, including power and
performance functions. SCMI provides two levels of abstraction, protocols
and transports. Protocols define individual groups of system control and
management messages. A protocol specification describes the messages
that it supports. Transports describe the method by which protocol
messages are communicated between agents and the platform.

This patch adds basic infrastructure to manage the message allocation,
initialisation, packing/unpacking and shared memory management.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

MAINTAINERS

@@ -13387,7 +13387,8 @@ F:	Documentation/devicetree/bindings/arm/arm,sc[mp]i.txt
 F:	drivers/clk/clk-scpi.c
 F:	drivers/cpufreq/scpi-cpufreq.c
 F:	drivers/firmware/arm_scpi.c
-F:	include/linux/scpi_protocol.h
+F:	drivers/firmware/arm_scmi/
+F:	include/linux/sc[mp]i_protocol.h
 
 SYSTEM RESET/SHUTDOWN DRIVERS
 M:	Sebastian Reichel <sre@kernel.org>

drivers/firmware/Kconfig

@@ -19,6 +19,27 @@ config ARM_PSCI_CHECKER
 	  on and off through hotplug, so for now torture tests and PSCI checker
 	  are mutually exclusive.
 
+config ARM_SCMI_PROTOCOL
+	bool "ARM System Control and Management Interface (SCMI) Message Protocol"
+	depends on ARM || ARM64 || COMPILE_TEST
+	depends on MAILBOX
+	help
+	  ARM System Control and Management Interface (SCMI) protocol is a
+	  set of operating system-independent software interfaces that are
+	  used in system management. SCMI is extensible and currently provides
+	  interfaces for: Discovery and self-description of the interfaces
+	  it supports, Power domain management which is the ability to place
+	  a given device or domain into the various power-saving states that
+	  it supports, Performance management which is the ability to control
+	  the performance of a domain that is composed of compute engines
+	  such as application processors and other accelerators, Clock
+	  management which is the ability to set and inquire rates on platform
+	  managed clocks and Sensor management which is the ability to read
+	  sensor data, and be notified of sensor value.
+
+	  This protocol library provides interface for all the client drivers
+	  making use of the features offered by the SCMI.
+
 config ARM_SCPI_PROTOCOL
 	tristate "ARM System Control and Power Interface (SCPI) Message Protocol"
 	depends on ARM || ARM64 || COMPILE_TEST

drivers/firmware/Makefile

@@ -25,6 +25,7 @@ obj-$(CONFIG_QCOM_SCM_32)	+= qcom_scm-32.o
 CFLAGS_qcom_scm-32.o :=$(call as-instr,.arch armv7-a\n.arch_extension sec,-DREQUIRES_SEC=1) -march=armv7-a
 obj-$(CONFIG_TI_SCI_PROTOCOL)	+= ti_sci.o
 
+obj-$(CONFIG_ARM_SCMI_PROTOCOL)	+= arm_scmi/
 obj-y				+= broadcom/
 obj-y				+= meson/
 obj-$(CONFIG_GOOGLE_FIRMWARE)	+= google/

drivers/firmware/arm_scmi/Makefile

+obj-y	= scmi-driver.o
+scmi-driver-y = driver.o

drivers/firmware/arm_scmi/common.h

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface (SCMI) Message Protocol
+ * driver common header file containing some definitions, structures
+ * and function prototypes used in all the different SCMI protocols.
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ */
+
+#include <linux/completion.h>
+#include <linux/scmi_protocol.h>
+#include <linux/types.h>
+
+/**
+ * struct scmi_msg_hdr - Message(Tx/Rx) header
+ *
+ * @id: The identifier of the command being sent
+ * @protocol_id: The identifier of the protocol used to send @id command
+ * @seq: The token to identify the message. when a message/command returns,
+ *       the platform returns the whole message header unmodified including
+ *	 the token.
+ */
+struct scmi_msg_hdr {
+	u8 id;
+	u8 protocol_id;
+	u16 seq;
+	u32 status;
+	bool poll_completion;
+};
+
+/**
+ * struct scmi_msg - Message(Tx/Rx) structure
+ *
+ * @buf: Buffer pointer
+ * @len: Length of data in the Buffer
+ */
+struct scmi_msg {
+	void *buf;
+	size_t len;
+};
+
+/**
+ * struct scmi_xfer - Structure representing a message flow
+ *
+ * @hdr: Transmit message header
+ * @tx: Transmit message
+ * @rx: Receive message, the buffer should be pre-allocated to store
+ *	message. If request-ACK protocol is used, we can reuse the same
+ *	buffer for the rx path as we use for the tx path.
+ * @done: completion event
+ */
+
+struct scmi_xfer {
+	void *con_priv;
+	struct scmi_msg_hdr hdr;
+	struct scmi_msg tx;
+	struct scmi_msg rx;
+	struct completion done;
+};
+
+void scmi_one_xfer_put(const struct scmi_handle *h, struct scmi_xfer *xfer);
+int scmi_do_xfer(const struct scmi_handle *h, struct scmi_xfer *xfer);
+int scmi_one_xfer_init(const struct scmi_handle *h, u8 msg_id, u8 prot_id,
+		       size_t tx_size, size_t rx_size, struct scmi_xfer **p);
+int scmi_handle_put(const struct scmi_handle *handle);
+struct scmi_handle *scmi_handle_get(struct device *dev);

include/linux/scmi_protocol.h

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SCMI Message Protocol driver header
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ */
+#include <linux/types.h>
+
+/**
+ * struct scmi_handle - Handle returned to ARM SCMI clients for usage.
+ *
+ * @dev: pointer to the SCMI device
+ */
+struct scmi_handle {
+	struct device *dev;
+};