[PATCH v2 3/4] clk: add clock driver for SCMI agents

[Etienne Carriere]

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

SCMI clock driver is embedded upon CONFIG_CLK_SCMI=y. If enabled,
CONFIG_SCMI_AGENT is also enabled.

SCMI Clock 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>
Cc: Lukasz Majewski <lukma at denx.de>
Cc: Simon Glass <sjg at chromium.org>
Cc: Peng Fan <peng.fan at nxp.com>
Cc: Sudeep Holla <sudeep.holla at arm.com>
---

Changes in v2:
- CONFIG_CLK_SCMI depends on CONFIG_SCMI_FIRMWARE instead of
  selecting CONFIG_SCMI_FIRMWARE.
- Add inline comment description for structures and moves them to
  source file top. Add/fixup some functions inline description comments.
- Replace rc with ret as return value local variable label.
- Fix scmi_clk_get_rate() return value to propagate error number.
- Fix scmi_clk_set_rate() to request synchronous rate set operation:
  drop flag SCMI_CLK_RATE_ASYNC_NORESP in the SCMI message payload.
- Fix scmi_clk_set_rate() return value to return clock effective rate
  on success.
---
 drivers/clk/Kconfig     |   8 ++
 drivers/clk/Makefile    |   1 +
 drivers/clk/clk_scmi.c  | 186 ++++++++++++++++++++++++++++++++++++++++
 drivers/firmware/scmi.c |   3 +
 4 files changed, 198 insertions(+)
 create mode 100644 drivers/clk/clk_scmi.c

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 6003e140b5..4dfbad7986 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -159,6 +159,14 @@ config CLK_CDCE9XX
 	   Enable the clock synthesizer driver for CDCE913/925/937/949
 	   series of chips.
 
+config CLK_SCMI
+	bool "Enable SCMI clock driver"
+	depends on SCMI_FIRMWARE
+	help
+	  Enable this option if you want to support clock devices exposed
+	  by a SCMI agent based on SCMI clock protocol communication
+	  with a SCMI server.
+
 source "drivers/clk/analogbits/Kconfig"
 source "drivers/clk/at91/Kconfig"
 source "drivers/clk/exynos/Kconfig"
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index cda4b4b605..d1e295ac7c 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_CLK_MPC83XX) += mpc83xx_clk.o
 obj-$(CONFIG_CLK_OCTEON) += clk_octeon.o
 obj-$(CONFIG_CLK_OWL) += owl/
 obj-$(CONFIG_CLK_RENESAS) += renesas/
+obj-$(CONFIG_CLK_SCMI) += clk_scmi.o
 obj-$(CONFIG_CLK_SIFIVE) += sifive/
 obj-$(CONFIG_ARCH_SUNXI) += sunxi/
 obj-$(CONFIG_CLK_STM32F) += clk_stm32f.o
diff --git a/drivers/clk/clk_scmi.c b/drivers/clk/clk_scmi.c
new file mode 100644
index 0000000000..6abeb1a4c4
--- /dev/null
+++ b/drivers/clk/clk_scmi.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019-2020 Linaro Limited
+ */
+#include <common.h>
+#include <clk-uclass.h>
+#include <dm.h>
+#include <scmi.h>
+#include <asm/types.h>
+
+enum scmi_clock_message_id {
+	SCMI_CLOCK_RATE_SET = 0x5,
+	SCMI_CLOCK_RATE_GET = 0x6,
+	SCMI_CLOCK_CONFIG_SET = 0x7,
+};
+
+#define SCMI_CLK_RATE_ASYNC_NOTIFY	BIT(0)
+#define SCMI_CLK_RATE_ASYNC_NORESP	(BIT(0) | BIT(1))
+#define SCMI_CLK_RATE_ROUND_DOWN	0
+#define SCMI_CLK_RATE_ROUND_UP		BIT(2)
+#define SCMI_CLK_RATE_ROUND_CLOSEST	BIT(3)
+
+/**
+ * struct scmi_clk_state_in - Message payload for CLOCK_CONFIG_SET command
+ * @clock_id:	SCMI clock ID
+ * @attributes:	Attributes of the targets clock state
+ */
+struct scmi_clk_state_in {
+	u32 clock_id;
+	u32 attributes;
+};
+
+/**
+ * struct scmi_clk_state_out - Response payload for CLOCK_CONFIG_SET command
+ * @status:	SCMI command status
+ */
+struct scmi_clk_state_out {
+	s32 status;
+};
+
+/**
+ * struct scmi_clk_state_in - Message payload for CLOCK_RATE_GET command
+ * @clock_id:	SCMI clock ID
+ * @attributes:	Attributes of the targets clock state
+ */
+struct scmi_clk_rate_get_in {
+	u32 clock_id;
+};
+
+/**
+ * struct scmi_clk_rate_get_out - Response payload for CLOCK_RATE_GET command
+ * @status:	SCMI command status
+ * @rate_lsb:	32bit LSB of the clock rate in Hertz
+ * @rate_msb:	32bit MSB of the clock rate in Hertz
+ */
+struct scmi_clk_rate_get_out {
+	s32 status;
+	u32 rate_lsb;
+	u32 rate_msb;
+};
+
+/**
+ * struct scmi_clk_state_in - Message payload for CLOCK_RATE_SET command
+ * @clock_id:	SCMI clock ID
+ * @flags:	Flags for the clock rate set request
+ * @rate_lsb:	32bit LSB of the clock rate in Hertz
+ * @rate_msb:	32bit MSB of the clock rate in Hertz
+ */
+struct scmi_clk_rate_set_in {
+	u32 clock_id;
+	u32 flags;
+	u32 rate_lsb;
+	u32 rate_msb;
+};
+
+/**
+ * struct scmi_clk_rate_set_out - Response payload for CLOCK_RATE_SET command
+ * @status:	SCMI command status
+ */
+struct scmi_clk_rate_set_out {
+	s32 status;
+};
+
+static int scmi_clk_gate(struct clk *clk, int enable)
+{
+	struct scmi_clk_state_in in = {
+		.clock_id = clk->id,
+		.attributes = enable,
+	};
+	struct scmi_clk_state_out out;
+	struct scmi_msg scmi_msg = {
+		.protocol_id = SCMI_PROTOCOL_ID_CLOCK,
+		.message_id = SCMI_CLOCK_CONFIG_SET,
+		.in_msg = (u8 *)&in,
+		.in_msg_sz = sizeof(in),
+		.out_msg = (u8 *)&out,
+		.out_msg_sz = sizeof(out),
+	};
+	int ret;
+
+	ret = scmi_send_and_process_msg(clk->dev->parent, &scmi_msg);
+	if (ret)
+		return ret;
+
+	return scmi_to_linux_errno(out.status);
+}
+
+static int scmi_clk_enable(struct clk *clk)
+{
+	return scmi_clk_gate(clk, 1);
+}
+
+static int scmi_clk_disable(struct clk *clk)
+{
+	return scmi_clk_gate(clk, 0);
+}
+
+static ulong scmi_clk_get_rate(struct clk *clk)
+{
+	struct scmi_clk_rate_get_in in = {
+		.clock_id = clk->id,
+	};
+	struct scmi_clk_rate_get_out out;
+	struct scmi_msg scmi_msg = {
+		.protocol_id = SCMI_PROTOCOL_ID_CLOCK,
+		.message_id = SCMI_CLOCK_RATE_GET,
+		.in_msg = (u8 *)&in,
+		.in_msg_sz = sizeof(in),
+		.out_msg = (u8 *)&out,
+		.out_msg_sz = sizeof(out),
+	};
+	int ret;
+
+	ret = scmi_send_and_process_msg(clk->dev->parent, &scmi_msg);
+	if (ret < 0)
+		return ret;
+
+	ret = scmi_to_linux_errno(out.status);
+	if (ret < 0)
+		return ret;
+
+	return (ulong)(((u64)out.rate_msb << 32) | out.rate_lsb);
+}
+
+static ulong scmi_clk_set_rate(struct clk *clk, ulong rate)
+{
+	struct scmi_clk_rate_set_in in = {
+		.clock_id = clk->id,
+		.flags = SCMI_CLK_RATE_ROUND_CLOSEST,
+		.rate_lsb = (u32)rate,
+		.rate_msb = (u32)((u64)rate >> 32),
+	};
+	struct scmi_clk_rate_set_out out;
+	struct scmi_msg scmi_msg = {
+		.protocol_id = SCMI_PROTOCOL_ID_CLOCK,
+		.message_id = SCMI_CLOCK_RATE_SET,
+		.in_msg = (u8 *)&in,
+		.in_msg_sz = sizeof(in),
+		.out_msg = (u8 *)&out,
+		.out_msg_sz = sizeof(out),
+	};
+	int ret;
+
+	ret = scmi_send_and_process_msg(clk->dev->parent, &scmi_msg);
+	if (ret < 0)
+		return ret;
+
+	ret = scmi_to_linux_errno(out.status);
+	if (ret < 0)
+		return ret;
+
+	return scmi_clk_get_rate(clk);
+}
+
+static const struct clk_ops scmi_clk_ops = {
+	.enable = scmi_clk_enable,
+	.disable = scmi_clk_disable,
+	.get_rate = scmi_clk_get_rate,
+	.set_rate = scmi_clk_set_rate,
+};
+
+U_BOOT_DRIVER(scmi_clock) = {
+	.name = "scmi_clk",
+	.id = UCLASS_CLK,
+	.ops = &scmi_clk_ops,
+};
diff --git a/drivers/firmware/scmi.c b/drivers/firmware/scmi.c
index 264f3d99c8..cddfa0bbc2 100644
--- a/drivers/firmware/scmi.c
+++ b/drivers/firmware/scmi.c
@@ -457,6 +457,9 @@ static int scmi_bind(struct udevice *dev)
 			continue;
 
 		switch (protocol_id) {
+		case SCMI_PROTOCOL_ID_CLOCK:
+			drv = DM_GET_DRIVER(scmi_clock);
+			break;
 		default:
 			dev_info(dev, "Ignore unsupported SCMI protocol %u\n",
 				 protocol_id);
-- 
2.17.1