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>

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 {

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 */

configs/sandbox_defconfig

@@ -132,6 +132,8 @@ CONFIG_BOARD_SANDBOX=y
 CONFIG_DMA=y
 CONFIG_DMA_CHANNELS=y
 CONFIG_SANDBOX_DMA=y
+CONFIG_FIRMWARE=y
+CONFIG_SCMI_FIRMWARE=y
 CONFIG_GPIO_HOG=y
 CONFIG_DM_GPIO_LOOKUP_LABEL=y
 CONFIG_PM8916_GPIO=y

drivers/firmware/Kconfig

@@ -36,3 +36,5 @@ config ZYNQMP_FIRMWARE
 	  various platform management services.
 	  Say yes to enable ZynqMP firmware interface driver.
 	  If in doubt, say N.
+
+source "drivers/firmware/scmi/Kconfig"

drivers/firmware/Makefile

@@ -3,3 +3,4 @@ obj-$(CONFIG_$(SPL_)ARM_PSCI_FW)	+= psci.o
 obj-$(CONFIG_TI_SCI_PROTOCOL)	+= ti_sci.o
 obj-$(CONFIG_SANDBOX)		+= firmware-sandbox.o
 obj-$(CONFIG_ZYNQMP_FIRMWARE)	+= firmware-zynqmp.o
+obj-$(CONFIG_SCMI_FIRMWARE)	+= scmi/

drivers/firmware/scmi/Kconfig

@@ -0,0 +1,17 @@
+config SCMI_FIRMWARE
+	bool "Enable SCMI support"
+	select FIRMWARE
+	select OF_TRANSLATE
+	depends on SANDBOX
+	help
+	  System Control and Management Interface (SCMI) is a communication
+	  protocol that defines standard interfaces for power, performance
+	  and system management. The SCMI specification is available at
+	  https://developer.arm.com/architectures/system-architectures/software-standards/scmi
+
+	  An SCMI agent communicates with a related SCMI server firmware
+	  located in another sub-system, as a companion micro controller
+	  or a companion host in the CPU system.
+
+	  Communications between agent (client) and the SCMI server are
+	  based on message exchange.

drivers/firmware/scmi/Makefile

@@ -0,0 +1,2 @@
+obj-y	+= scmi_agent-uclass.o
+obj-$(CONFIG_SANDBOX)		+= sandbox-scmi_agent.o

drivers/firmware/scmi/sandbox-scmi_agent.c

@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020, Linaro Limited
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <malloc.h>
+#include <scmi_agent.h>
+#include <scmi_agent-uclass.h>
+#include <scmi_protocols.h>
+#include <asm/io.h>
+#include <asm/scmi_test.h>
+#include <dm/device_compat.h>
+
+/*
+ * The sandbox SCMI agent driver simulates to some extend a SCMI message
+ * processing. It simulates few of the SCMI services for some of the
+ * SCMI protocols embedded in U-Boot. Currently none.
+ *
+ * This driver simulates 2 SCMI agents for test purpose.
+ *
+ * This Driver exports sandbox_scmi_service_ct() for the test sequence to
+ * get the state of the simulated services (clock state, rate, ...) and
+ * check back-end device state reflects the request send through the
+ * various uclass devices, currently nothing.
+ */
+
+#define SANDBOX_SCMI_AGENT_COUNT	2
+
+/* The list saves to simulted end devices references for test purpose */
+struct sandbox_scmi_agent *sandbox_scmi_agent_list[SANDBOX_SCMI_AGENT_COUNT];
+
+static struct sandbox_scmi_service sandbox_scmi_service_state = {
+	.agent = sandbox_scmi_agent_list,
+	.agent_count = SANDBOX_SCMI_AGENT_COUNT,
+};
+
+struct sandbox_scmi_service *sandbox_scmi_service_ctx(void)
+{
+	return &sandbox_scmi_service_state;
+}
+
+static void debug_print_agent_state(struct udevice *dev, char *str)
+{
+	struct sandbox_scmi_agent *agent = dev_get_priv(dev);
+
+	dev_dbg(dev, "Dump sandbox_scmi_agent %u: %s\n", agent->idx, str);
+};
+
+static int sandbox_scmi_test_process_msg(struct udevice *dev,
+					 struct scmi_msg *msg)
+{
+	switch (msg->protocol_id) {
+	case SCMI_PROTOCOL_ID_BASE:
+	case SCMI_PROTOCOL_ID_POWER_DOMAIN:
+	case SCMI_PROTOCOL_ID_SYSTEM:
+	case SCMI_PROTOCOL_ID_PERF:
+	case SCMI_PROTOCOL_ID_CLOCK:
+	case SCMI_PROTOCOL_ID_SENSOR:
+	case SCMI_PROTOCOL_ID_RESET_DOMAIN:
+		*(u32 *)msg->out_msg = SCMI_NOT_SUPPORTED;
+		return 0;
+	default:
+		break;
+	}
+
+	dev_err(dev, "%s(%s): Unhandled protocol_id %#x/message_id %#x\n",
+		__func__, dev->name, msg->protocol_id, msg->message_id);
+
+	if (msg->out_msg_sz < sizeof(u32))
+		return -EINVAL;
+
+	/* Intentionnaly report unhandled IDs through the SCMI return code */
+	*(u32 *)msg->out_msg = SCMI_PROTOCOL_ERROR;
+	return 0;
+}
+
+static int sandbox_scmi_test_remove(struct udevice *dev)
+{
+	struct sandbox_scmi_agent *agent = dev_get_priv(dev);
+
+	debug_print_agent_state(dev, "removed");
+
+	/* We only need to dereference the agent in the context */
+	sandbox_scmi_service_ctx()->agent[agent->idx] = NULL;
+
+	return 0;
+}
+
+static int sandbox_scmi_test_probe(struct udevice *dev)
+{
+	static const char basename[] = "sandbox-scmi-agent@";
+	struct sandbox_scmi_agent *agent = dev_get_priv(dev);
+	const size_t basename_size = sizeof(basename) - 1;
+
+	if (strncmp(basename, dev->name, basename_size))
+		return -ENOENT;
+
+	switch (dev->name[basename_size]) {
+	case '0':
+		*agent = (struct sandbox_scmi_agent){
+			.idx = 0,
+		};
+		break;
+	case '1':
+		*agent = (struct sandbox_scmi_agent){
+			.idx = 1,
+		};
+		break;
+	default:
+		dev_err(dev, "%s(): Unexpected agent ID %s\n",
+			__func__, dev->name + basename_size);
+		return -ENOENT;
+	}
+
+	debug_print_agent_state(dev, "probed");
+
+	/* Save reference for tests purpose */
+	sandbox_scmi_service_ctx()->agent[agent->idx] = agent;
+
+	return 0;
+};
+
+static const struct udevice_id sandbox_scmi_test_ids[] = {
+	{ .compatible = "sandbox,scmi-agent" },
+	{ }
+};
+
+struct scmi_agent_ops sandbox_scmi_test_ops = {
+	.process_msg = sandbox_scmi_test_process_msg,
+};
+
+U_BOOT_DRIVER(sandbox_scmi_agent) = {
+	.name = "sandbox-scmi_agent",
+	.id = UCLASS_SCMI_AGENT,
+	.of_match = sandbox_scmi_test_ids,
+	.priv_auto_alloc_size = sizeof(struct sandbox_scmi_agent),
+	.probe = sandbox_scmi_test_probe,
+	.remove = sandbox_scmi_test_remove,
+	.ops = &sandbox_scmi_test_ops,
+};

drivers/firmware/scmi/scmi_agent-uclass.c

@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2020 Linaro Limited.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <scmi_agent-uclass.h>
+#include <scmi_protocols.h>
+
+#include <dm/device-internal.h>
+#include <linux/compat.h>
+
+/**
+ * struct error_code - Helper structure for SCMI error code conversion
+ * @scmi:	SCMI error code
+ * @errno:	Related standard error number
+ */
+struct error_code {
+	int scmi;
+	int errno;
+};
+
+static const struct error_code scmi_linux_errmap[] = {
+	{ .scmi = SCMI_NOT_SUPPORTED, .errno = -EOPNOTSUPP, },
+	{ .scmi = SCMI_INVALID_PARAMETERS, .errno = -EINVAL, },
+	{ .scmi = SCMI_DENIED, .errno = -EACCES, },
+	{ .scmi = SCMI_NOT_FOUND, .errno = -ENOENT, },
+	{ .scmi = SCMI_OUT_OF_RANGE, .errno = -ERANGE, },
+	{ .scmi = SCMI_BUSY, .errno = -EBUSY, },
+	{ .scmi = SCMI_COMMS_ERROR, .errno = -ECOMM, },
+	{ .scmi = SCMI_GENERIC_ERROR, .errno = -EIO, },
+	{ .scmi = SCMI_HARDWARE_ERROR, .errno = -EREMOTEIO, },
+	{ .scmi = SCMI_PROTOCOL_ERROR, .errno = -EPROTO, },
+};
+
+int scmi_to_linux_errno(s32 scmi_code)
+{
+	int n;
+
+	if (!scmi_code)
+		return 0;
+
+	for (n = 0; n < ARRAY_SIZE(scmi_linux_errmap); n++)
+		if (scmi_code == scmi_linux_errmap[n].scmi)
+			return scmi_linux_errmap[1].errno;
+
+	return -EPROTO;
+}
+
+/*
+ * SCMI agent devices binds devices of various uclasses depeding on
+ * the FDT description. scmi_bind_protocol() is a generic bind sequence
+ * called by the uclass at bind stage, that is uclass post_bind.
+ */
+static int scmi_bind_protocols(struct udevice *dev)
+{
+	int ret = 0;
+	ofnode node;
+	struct driver *drv;
+
+	dev_for_each_subnode(node, dev) {
+		u32 protocol_id;
+
+		if (!ofnode_is_available(node))
+			continue;
+
+		if (ofnode_read_u32(node, "reg", &protocol_id))
+			continue;
+
+		switch (protocol_id) {
+		default:
+			dev_info(dev, "Ignore unsupported SCMI protocol %#x\n",
+				 protocol_id);
+			continue;
+		}
+
+		ret = device_bind_ofnode(dev, drv, ofnode_get_name(node),
+					 NULL, node, NULL);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+static const struct scmi_agent_ops *transport_dev_ops(struct udevice *dev)
+{
+	return (const struct scmi_agent_ops *)dev->driver->ops;
+}
+
+int devm_scmi_process_msg(struct udevice *dev, struct scmi_msg *msg)
+{
+	const struct scmi_agent_ops *ops = transport_dev_ops(dev);
+
+	if (ops->process_msg)
+		return ops->process_msg(dev, msg);
+
+	return -EPROTONOSUPPORT;
+}
+
+UCLASS_DRIVER(scmi_agent) = {
+	.id		= UCLASS_SCMI_AGENT,
+	.name		= "scmi_agent",
+	.post_bind	= scmi_bind_protocols,
+};

include/dm/uclass-id.h

@@ -94,6 +94,7 @@ enum uclass_id {
 	UCLASS_RESET,		/* Reset controller device */
 	UCLASS_RNG,		/* Random Number Generator */
 	UCLASS_RTC,		/* Real time clock device */
+	UCLASS_SCMI_AGENT,	/* Interface with an SCMI server */
 	UCLASS_SCSI,		/* SCSI device */
 	UCLASS_SERIAL,		/* Serial UART */
 	UCLASS_SIMPLE_BUS,	/* Bus with child devices */

include/scmi_agent-uclass.h

@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2019-2020 Linaro Limited.
+ */
+#ifndef _SCMI_AGENT_UCLASS_H
+#define _SCMI_AGENT_UCLASS_H
+
+struct udevice;
+struct scmi_msg;
+
+/**
+ * struct scmi_transport_ops - The functions that a SCMI transport layer must implement.
+ */
+struct scmi_agent_ops {
+	/*
+	 * process_msg - Request transport to get the SCMI message processed
+	 *
+	 * @agent:		Agent using the transport
+	 * @msg:		SCMI message to be transmitted
+	 */
+	int (*process_msg)(struct udevice *dev, struct scmi_msg *msg);
+};
+
+#endif /* _SCMI_TRANSPORT_UCLASS_H */

include/scmi_agent.h

@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
+/*
+ * Copyright (c) 2015-2019, Arm Limited and Contributors. All rights reserved.
+ * Copyright (C) 2019-2020, Linaro Limited
+ *
+ * An SCMI agent device represent on communication path from a
+ * device driver to the remote SCMI server which driver sends
+ * messages to and receives response messages from.
+ */
+#ifndef SCMI_AGENT_H
+#define SCMI_AGENT_H
+
+#include <asm/types.h>
+
+struct udevice;
+
+/*
+ * struct scmi_msg - Context of a SCMI message sent and the response received
+ *
+ * @protocol_id:	SCMI protocol ID
+ * @message_id:		SCMI message ID for a defined protocol ID
+ * @in_msg:		Pointer to the message payload sent by the driver
+ * @in_msg_sz:		Byte size of the message payload sent
+ * @out_msg:		Pointer to buffer to store response message payload
+ * @out_msg_sz:		Byte size of the response buffer and response payload
+ */
+struct scmi_msg {
+	unsigned int protocol_id;
+	unsigned int message_id;
+	u8 *in_msg;
+	size_t in_msg_sz;
+	u8 *out_msg;
+	size_t out_msg_sz;
+};
+
+/* Helper macro to match a message on input/output array references */
+#define SCMI_MSG_IN(_protocol, _message, _in_array, _out_array) \
+	(struct scmi_msg){			\
+		.protocol_id = (_protocol),	\
+		.message_id = (_message),	\
+		.in_msg = (uint8_t *)&(_in_array),	\
+		.in_msg_sz = sizeof(_in_array),	\
+		.out_msg = (uint8_t *)&(_out_array),	\
+		.out_msg_sz = sizeof(_out_array),	\
+	}
+
+/**
+ * scmi_send_and_process_msg() - send and process a SCMI message
+ *
+ * Send a message to a SCMI server through a target SCMI agent device.
+ * Caller sets scmi_msg::out_msg_sz to the output message buffer size.
+ * On return, scmi_msg::out_msg_sz stores the response payload size.
+ *
+ * @dev:	SCMI agent device
+ * @msg:	Message structure reference
+ * @return 0 on success and a negative errno on failure
+ */
+int devm_scmi_process_msg(struct udevice *dev, struct scmi_msg *msg);
+
+/**
+ * scmi_to_linux_errno() - Convert an SCMI error code into a Linux errno code
+ *
+ * @scmi_errno:	SCMI error code value
+ * @return 0 for successful status and a negative errno otherwise
+ */
+int scmi_to_linux_errno(s32 scmi_errno);
+
+#endif /* SCMI_H */

include/scmi_protocols.h

@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
+/*
+ * Copyright (c) 2015-2019, Arm Limited and Contributors. All rights reserved.
+ * Copyright (C) 2019-2020, Linaro Limited
+ */
+#ifndef _SCMI_PROTOCOLS_H
+#define _SCMI_PROTOCOLS_H
+
+#include <linux/bitops.h>
+
+/*
+ * Subset the SCMI protocols definition
+ * based on SCMI specification v2.0 (DEN0056B)
+ * https://developer.arm.com/docs/den0056/b
+ */
+
+enum scmi_std_protocol {
+	SCMI_PROTOCOL_ID_BASE = 0x10,
+	SCMI_PROTOCOL_ID_POWER_DOMAIN = 0x11,
+	SCMI_PROTOCOL_ID_SYSTEM = 0x12,
+	SCMI_PROTOCOL_ID_PERF = 0x13,
+	SCMI_PROTOCOL_ID_CLOCK = 0x14,
+	SCMI_PROTOCOL_ID_SENSOR = 0x15,
+	SCMI_PROTOCOL_ID_RESET_DOMAIN = 0x16,
+};
+
+enum scmi_status_code {
+	SCMI_SUCCESS =  0,
+	SCMI_NOT_SUPPORTED = -1,
+	SCMI_INVALID_PARAMETERS = -2,
+	SCMI_DENIED = -3,
+	SCMI_NOT_FOUND = -4,
+	SCMI_OUT_OF_RANGE = -5,
+	SCMI_BUSY = -6,
+	SCMI_COMMS_ERROR = -7,
+	SCMI_GENERIC_ERROR = -8,
+	SCMI_HARDWARE_ERROR = -9,
+	SCMI_PROTOCOL_ERROR = -10,
+};
+
+#endif /* _SCMI_PROTOCOLS_H */

test/dm/Makefile

@@ -80,4 +80,5 @@ obj-$(CONFIG_DM_RNG) += rng.o
 obj-$(CONFIG_CLK_K210_SET_RATE) += k210_pll.o
 obj-$(CONFIG_SIMPLE_PM_BUS) += simple-pm-bus.o
 obj-$(CONFIG_RESET_SYSCON) += syscon-reset.o
+obj-$(CONFIG_SCMI_FIRMWARE) += scmi.o
 endif

test/dm/scmi.c

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020, Linaro Limited
+ *
+ * Tests scmi_agent uclass and the SCMI drivers implemented in other
+ * uclass devices probe when a SCMI server exposes resources.
+ *
+ * Note in test.dts the protocol@10 node in agent 1. Protocol 0x10 is not
+ * implemented in U-Boot SCMI components but the implementation is exepected
+ * to not complain on unknown protocol IDs, as long as it is not used. Note
+ * in test.dts tests that SCMI drivers probing does not fail for such an
+ * unknown SCMI protocol ID.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <asm/scmi_test.h>
+#include <dm/device-internal.h>
+#include <dm/test.h>
+#include <test/ut.h>
+
+/*
+ * Test SCMI states when loading and releasing resources
+ * related to SCMI drivers.
+ */
+static int dm_test_scmi_sandbox_agent(struct unit_test_state *uts)
+{
+	struct sandbox_scmi_service *scmi_ctx = sandbox_scmi_service_ctx();
+
+	ut_assertnonnull(scmi_ctx);
+	ut_asserteq(2, scmi_ctx->agent_count);
+	ut_assertnull(scmi_ctx->agent[0]);
+	ut_assertnull(scmi_ctx->agent[1]);
+
+	return 0;
+}
+
+DM_TEST(dm_test_scmi_sandbox_agent, UT_TESTF_SCAN_FDT);