[PATCH 4/4] reset: add reset controller driver for SCMI agents

[Etienne Carriere]

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 at linaro.org>
---

 drivers/firmware/scmi.c    |  3 ++
 drivers/reset/Kconfig      |  8 ++++
 drivers/reset/Makefile     |  1 +
 drivers/reset/reset-scmi.c | 86 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 98 insertions(+)
 create mode 100644 drivers/reset/reset-scmi.c

diff --git a/drivers/firmware/scmi.c b/drivers/firmware/scmi.c
index 9f06718df51..9be53a9cf11 100644
--- a/drivers/firmware/scmi.c
+++ b/drivers/firmware/scmi.c
@@ -402,6 +402,9 @@ static int scmi_bind(struct udevice *dev)
 		case SCMI_PROTOCOL_ID_CLOCK:
 			drv = DM_GET_DRIVER(scmi_clock);
 			break;
+		case SCMI_PROTOCOL_ID_RESET_DOMAIN:
+			drv = DM_GET_DRIVER(scmi_reset_domain);
+			break;
 		default:
 			dev_info(dev, "Ignore unsupported SCMI protocol %u\n",
 				 protocol_id);
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index 6d535612234..31bd4cd5b45 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -164,4 +164,12 @@ 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 8e0124b8dee..f3c0fbfd8f3 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -25,3 +25,4 @@ obj-$(CONFIG_RESET_HISILICON) += reset-hisilicon.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.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 00000000000..e664d91d865
--- /dev/null
+++ b/drivers/reset/reset-scmi.c
@@ -0,0 +1,86 @@
+// 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.h>
+#include <asm/types.h>
+
+enum scmi_reset_domain_message_id {
+	SCMI_RESET_DOMAIN_RESET = 0x4,
+};
+
+#define SCMI_RD_RESET_FLAG_ASSERT	BIT(1)
+#define SCMI_RD_RESET_FLAG_DEASSERT	0
+
+struct scmi_rd_reset_in {
+	u32 domain_id;
+	u32 flags;
+	u32 reset_state;
+};
+
+struct scmi_rd_reset_out {
+	s32 status;
+};
+
+static int scmi_reset_set_state(struct reset_ctl *rst, int assert_not_deassert)
+{
+	struct scmi_rd_reset_in in = {
+		.domain_id = rst->id,
+		.flags = assert_not_deassert ? SCMI_RD_RESET_FLAG_ASSERT :
+			 SCMI_RD_RESET_FLAG_DEASSERT,
+		.reset_state = 0,
+	};
+	struct scmi_rd_reset_out out;
+	struct scmi_msg scmi_msg = {
+		.protocol_id = SCMI_PROTOCOL_ID_RESET_DOMAIN,
+		.message_id = SCMI_RESET_DOMAIN_RESET,
+		.in_msg = (u8 *)&in,
+		.in_msg_sz = sizeof(in),
+		.out_msg = (u8 *)&out,
+		.out_msg_sz = sizeof(out),
+	};
+	int rc;
+
+	rc = scmi_send_and_process_msg(rst->dev->parent, &scmi_msg);
+	if (rc)
+		return rc;
+
+	return scmi_to_linux_errno(out.status);
+}
+
+static int scmi_reset_assert(struct reset_ctl *rst)
+{
+	return scmi_reset_set_state(rst, SCMI_RD_RESET_FLAG_ASSERT);
+}
+
+static int scmi_reset_deassert(struct reset_ctl *rst)
+{
+	return scmi_reset_set_state(rst, SCMI_RD_RESET_FLAG_DEASSERT);
+}
+
+static int scmi_reset_request(struct reset_ctl *reset_ctl)
+{
+	return 0;
+}
+
+static int scmi_reset_rfree(struct reset_ctl *reset_ctl)
+{
+	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,
+};
-- 
2.17.1