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>

3 files changed, 90 insertions, 0 deletions

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 3fdfe4a..b60e11f 100644
--- a/drivers/reset/Kconfig
+++ b/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
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 5176da5..10a7973 100644
--- a/drivers/reset/Makefile
+++ b/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
diff --git a/drivers/reset/reset-scmi.c b/drivers/reset/reset-scmi.c
new file mode 100644
index 0000000..1bff807
--- /dev/null
+++ b/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,
+};