reset: add reset controller driver for SCMI agents

This change introduces a reset controller driver for SCMI agent devices.
When SCMI agent and SCMI reset domain drivers are enabled, SCMI agent
binds a reset controller device for each SCMI reset domain protocol
devices enabled in the FDT.

SCMI reset driver is embedded upon CONFIG_RESET_SCMI=y. If enabled,
CONFIG_SCMI_AGENT is also enabled.

SCMI Reset Domain protocol is defined in the SCMI specification [1].

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>

drivers/firmware/scmi/scmi_agent-uclass.c

@@ -74,6 +74,10 @@ static int scmi_bind_protocols(struct udevice *dev)
 			if (IS_ENABLED(CONFIG_CLK_SCMI))
 				drv = DM_GET_DRIVER(scmi_clock);
 			break;
+		case SCMI_PROTOCOL_ID_RESET_DOMAIN:
+			if (IS_ENABLED(CONFIG_RESET_SCMI))
+				drv = DM_GET_DRIVER(scmi_reset_domain);
+			break;
 		default:
 			break;
 		}

drivers/reset/Kconfig

@@ -181,4 +181,12 @@ config RESET_RASPBERRYPI
 	  relevant. This driver provides a reset controller capable of
 	  interfacing with RPi4's co-processor and model these firmware
 	  initialization routines as reset lines.
+
+config RESET_SCMI
+	bool "Enable SCMI reset domain driver"
+	select SCMI_FIRMWARE
+	help
+	  Enable this option if you want to support reset controller
+	  devices exposed by a SCMI agent based on SCMI reset domain
+	  protocol communication with a SCMI server.
 endmenu

drivers/reset/Makefile

@@ -27,3 +27,4 @@ obj-$(CONFIG_RESET_IPQ419) += reset-ipq4019.o
 obj-$(CONFIG_RESET_SIFIVE) += reset-sifive.o
 obj-$(CONFIG_RESET_SYSCON) += reset-syscon.o
 obj-$(CONFIG_RESET_RASPBERRYPI) += reset-raspberrypi.o
+obj-$(CONFIG_RESET_SCMI) += reset-scmi.o

drivers/reset/reset-scmi.c

@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019-2020 Linaro Limited
+ */
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <reset-uclass.h>
+#include <scmi_agent.h>
+#include <scmi_protocols.h>
+#include <asm/types.h>
+
+static int scmi_reset_set_level(struct reset_ctl *rst, bool assert_not_deassert)
+{
+	struct scmi_rd_reset_in in = {
+		.domain_id = rst->id,
+		.flags = assert_not_deassert ? SCMI_RD_RESET_FLAG_ASSERT : 0,
+		.reset_state = 0,
+	};
+	struct scmi_rd_reset_out out;
+	struct scmi_msg msg = SCMI_MSG_IN(SCMI_PROTOCOL_ID_RESET_DOMAIN,
+					  SCMI_RESET_DOMAIN_RESET,
+					  in, out);
+	int ret;
+
+	ret = devm_scmi_process_msg(rst->dev->parent, &msg);
+	if (ret)
+		return ret;
+
+	return scmi_to_linux_errno(out.status);
+}
+
+static int scmi_reset_assert(struct reset_ctl *rst)
+{
+	return scmi_reset_set_level(rst, true);
+}
+
+static int scmi_reset_deassert(struct reset_ctl *rst)
+{
+	return scmi_reset_set_level(rst, false);
+}
+
+static int scmi_reset_request(struct reset_ctl *rst)
+{
+	struct scmi_rd_attr_in in = {
+		.domain_id = rst->id,
+	};
+	struct scmi_rd_attr_out out;
+	struct scmi_msg msg = SCMI_MSG_IN(SCMI_PROTOCOL_ID_RESET_DOMAIN,
+					  SCMI_RESET_DOMAIN_ATTRIBUTES,
+					  in, out);
+	int ret;
+
+	/*
+	 * We don't really care about the attribute, just check
+	 * the reset domain exists.
+	 */
+	ret = devm_scmi_process_msg(rst->dev->parent, &msg);
+	if (ret)
+		return ret;
+
+	return scmi_to_linux_errno(out.status);
+}
+
+static int scmi_reset_rfree(struct reset_ctl *rst)
+{
+	return 0;
+}
+
+static const struct reset_ops scmi_reset_domain_ops = {
+	.request	= scmi_reset_request,
+	.rfree		= scmi_reset_rfree,
+	.rst_assert	= scmi_reset_assert,
+	.rst_deassert	= scmi_reset_deassert,
+};
+
+U_BOOT_DRIVER(scmi_reset_domain) = {
+	.name = "scmi_reset_domain",
+	.id = UCLASS_RESET,
+	.ops = &scmi_reset_domain_ops,
+};

include/scmi_protocols.h

@@ -116,4 +116,64 @@ struct scmi_clk_rate_set_out {
 	s32 status;
 };
 
+/*
+ * SCMI Reset Domain Protocol
+ */
+
+enum scmi_reset_domain_message_id {
+	SCMI_RESET_DOMAIN_ATTRIBUTES = 0x3,
+	SCMI_RESET_DOMAIN_RESET = 0x4,
+};
+
+#define SCMI_RD_NAME_LEN		16
+
+#define SCMI_RD_ATTRIBUTES_FLAG_ASYNC	BIT(31)
+#define SCMI_RD_ATTRIBUTES_FLAG_NOTIF	BIT(30)
+
+#define SCMI_RD_RESET_FLAG_ASYNC	BIT(2)
+#define SCMI_RD_RESET_FLAG_ASSERT	BIT(1)
+#define SCMI_RD_RESET_FLAG_CYCLE	BIT(0)
+
+/**
+ * struct scmi_rd_attr_in - Payload for RESET_DOMAIN_ATTRIBUTES message
+ * @domain_id:	SCMI reset domain ID
+ */
+struct scmi_rd_attr_in {
+	u32 domain_id;
+};
+
+/**
+ * struct scmi_rd_attr_out - Payload for RESET_DOMAIN_ATTRIBUTES response
+ * @status:	SCMI command status
+ * @attributes:	Retrieved attributes of the reset domain
+ * @latency:	Reset cycle max lantency
+ * @name:	Reset domain name
+ */
+struct scmi_rd_attr_out {
+	s32 status;
+	u32 attributes;
+	u32 latency;
+	char name[SCMI_RD_NAME_LEN];
+};
+
+/**
+ * struct scmi_rd_reset_in - Message payload for RESET command
+ * @domain_id:		SCMI reset domain ID
+ * @flags:		Flags for the reset request
+ * @reset_state:	Reset target state
+ */
+struct scmi_rd_reset_in {
+	u32 domain_id;
+	u32 flags;
+	u32 reset_state;
+};
+
+/**
+ * struct scmi_rd_reset_out - Response payload for RESET command
+ * @status:	SCMI command status
+ */
+struct scmi_rd_reset_out {
+	s32 status;
+};
+
 #endif /* _SCMI_PROTOCOLS_H */