clk: Introduce TI System Control Interface (TI SCI) clock driver

Some TI Keystone 2 and K3 family of SoCs contain a system controller
(like the Power Management Micro Controller (PMMC) on 66AK2G SoCs and
the Device Management and Security Controller on AM65x SoCs) that manage
the low-level device control (like clocks, resets etc) for the various
hardware modules present on the SoC. These device control operations are
provided to the host processor OS through a communication protocol
called the TI System Control Interface (TI SCI) protocol.

This patch adds a clock driver that communicates to the system
controller over the TI SCI protocol for performing clock management of
various devices present on the SoC. Various clock functionality is
achieved by the means of different TI SCI device operations provided by
the TI SCI framework.

This code is loosely based on the drivers/clk/keystone/sci-clk.c driver
of the Linux kernel.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>

doc/device-tree-bindings/clock/ti,sci-clk.txt

@@ -0,0 +1,53 @@
+Texas Instruments TI SCI Clock Controller
+=========================================
+
+All clocks on Texas Instruments' SoCs that contain a System Controller,
+are only controlled by this entity. Communication between a host processor
+running an OS and the System Controller happens through a protocol known
+as TI SCI[1]. This clock implementation plugs into the common clock
+framework and makes use of the TI SCI protocol on clock API requests.
+
+[1] http://processors.wiki.ti.com/index.php/TISCI
+
+Clock Controller Node
+=====================
+The clock controller node represents the clocks managed by the SYSFW. Because
+this relies on the TI SCI protocol to communicate with the SYSFW it must be a
+child of the sysfw node.
+
+Required Properties:
+--------------------
+- compatible: Must be "ti,k2g-sci-clk"
+- #clock-cells: Must be be 2. In clock consumers, this cell represents the
+		device ID and clock ID exposed by the SYSFW firmware.
+
+Example (AM65x):
+----------------
+	dmsc: dmsc {
+		compatible = "ti,k2g-sci";
+		...
+		k3_clks: clocks {
+			compatible = "ti,k2g-sci-clk";
+			#clock-cells = <2>;
+		};
+	};
+
+Clock Consumers
+===============
+Hardware blocks supplied by a clock should contain a "clocks" property that is
+a phandle pointing to the clock controller node along with an index representing
+the device id together with a clock ID to be passed to the SYSFW for device
+control.
+
+Required Properties:
+--------------------
+- clocks: phandle pointing to the corresponding clock node, an ID representing
+	  the device, and an index representing a clock.
+
+Example (AM65x):
+----------------
+	uart2: serial@02800000 {
+		compatible = "ti,omap4-uart";
+		...
+		clocks = <&k3_clks 0x0007 1>;
+	};

drivers/clk/Kconfig

@@ -54,6 +54,14 @@ config CLK_STM32F
 	  This clock driver adds support for RCC clock management
 	  for STM32F4 and STM32F7 SoCs.
 
+config CLK_TI_SCI
+	bool "TI System Control Interface (TI SCI) clock driver"
+	depends on CLK && TI_SCI_PROTOCOL && OF_CONTROL
+	help
+	  This enables the clock driver support over TI System Control Interface
+	  available on some new TI's SoCs. If you wish to use clock resources
+	  managed by the TI System Controller, say Y here. Otherwise, say N.
+
 config CLK_HSDK
 	bool "Enable cgu clock driver for HSDK"
 	depends on CLK

drivers/clk/Makefile

@@ -30,3 +30,4 @@ obj-$(CONFIG_MACH_PIC32) += clk_pic32.o
 obj-$(CONFIG_SANDBOX) += clk_sandbox.o
 obj-$(CONFIG_SANDBOX) += clk_sandbox_test.o
 obj-$(CONFIG_STM32H7) += clk_stm32h7.o
+obj-$(CONFIG_CLK_TI_SCI) += clk-ti-sci.o

drivers/clk/clk-ti-sci.c

@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Texas Instruments System Control Interface (TI SCI) clock driver
+ *
+ * Copyright (C) 2018 Texas Instruments Incorporated - http://www.ti.com/
+ *	Andreas Dannenberg <dannenberg@ti.com>
+ *
+ * Loosely based on Linux kernel sci-clk.c...
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <clk-uclass.h>
+#include <linux/soc/ti/ti_sci_protocol.h>
+
+/**
+ * struct ti_sci_clk_data - clock controller information structure
+ * @sci: TI SCI handle used for communication with system controller
+ */
+struct ti_sci_clk_data {
+	const struct ti_sci_handle *sci;
+};
+
+static int ti_sci_clk_probe(struct udevice *dev)
+{
+	struct ti_sci_clk_data *data = dev_get_priv(dev);
+
+	debug("%s(dev=%p)\n", __func__, dev);
+
+	if (!data)
+		return -ENOMEM;
+
+	/* Store handle for communication with the system controller */
+	data->sci = ti_sci_get_handle(dev);
+	if (IS_ERR(data->sci))
+		return PTR_ERR(data->sci);
+
+	return 0;
+}
+
+static int ti_sci_clk_of_xlate(struct clk *clk,
+			       struct ofnode_phandle_args *args)
+{
+	debug("%s(clk=%p, args_count=%d)\n", __func__, clk, args->args_count);
+
+	if (args->args_count != 2) {
+		debug("Invalid args_count: %d\n", args->args_count);
+		return -EINVAL;
+	}
+
+	/*
+	 * On TI SCI-based devices, the clock provider id field is used as a
+	 * device ID, and the data field is used as the associated sub-ID.
+	 */
+	clk->id = args->args[0];
+	clk->data = args->args[1];
+
+	return 0;
+}
+
+static int ti_sci_clk_request(struct clk *clk)
+{
+	debug("%s(clk=%p)\n", __func__, clk);
+	return 0;
+}
+
+static int ti_sci_clk_free(struct clk *clk)
+{
+	debug("%s(clk=%p)\n", __func__, clk);
+	return 0;
+}
+
+static ulong ti_sci_clk_get_rate(struct clk *clk)
+{
+	struct ti_sci_clk_data *data = dev_get_priv(clk->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_clk_ops *cops = &sci->ops.clk_ops;
+	u64 current_freq;
+	int ret;
+
+	debug("%s(clk=%p)\n", __func__, clk);
+
+	ret = cops->get_freq(sci, clk->id, clk->data, &current_freq);
+	if (ret) {
+		dev_err(clk->dev, "%s: get_freq failed (%d)\n", __func__, ret);
+		return ret;
+	}
+
+	debug("%s(current_freq=%llu)\n", __func__, current_freq);
+
+	return current_freq;
+}
+
+static ulong ti_sci_clk_set_rate(struct clk *clk, ulong rate)
+{
+	struct ti_sci_clk_data *data = dev_get_priv(clk->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_clk_ops *cops = &sci->ops.clk_ops;
+	int ret;
+
+	debug("%s(clk=%p, rate=%lu)\n", __func__, clk, rate);
+
+	/* Ask for exact frequency by using same value for min/target/max */
+	ret = cops->set_freq(sci, clk->id, clk->data, rate, rate, rate);
+	if (ret)
+		dev_err(clk->dev, "%s: set_freq failed (%d)\n", __func__, ret);
+
+	return ret;
+}
+
+static int ti_sci_clk_set_parent(struct clk *clk, struct clk *parent)
+{
+	struct ti_sci_clk_data *data = dev_get_priv(clk->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_clk_ops *cops = &sci->ops.clk_ops;
+	u8 num_parents;
+	u8 parent_cid;
+	int ret;
+
+	debug("%s(clk=%p, parent=%p)\n", __func__, clk, parent);
+
+	/* Make sure the clock parent is valid for a given device ID */
+	if (clk->id != parent->id)
+		return -EINVAL;
+
+	/* Make sure clock has parents that can be set */
+	ret = cops->get_num_parents(sci, clk->id, clk->data, &num_parents);
+	if (ret) {
+		dev_err(clk->dev, "%s: get_num_parents failed (%d)\n",
+			__func__, ret);
+		return ret;
+	}
+	if (num_parents < 2) {
+		dev_err(clk->dev, "%s: clock has no settable parents!\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	/* Make sure parent clock ID is valid */
+	parent_cid = parent->data - clk->data - 1;
+	if (parent_cid >= num_parents) {
+		dev_err(clk->dev, "%s: invalid parent clock!\n", __func__);
+		return -EINVAL;
+	}
+
+	/* Ready to proceed to configure the new clock parent */
+	ret = cops->set_parent(sci, clk->id, clk->data, parent->data);
+	if (ret)
+		dev_err(clk->dev, "%s: set_parent failed (%d)\n", __func__,
+			ret);
+
+	return ret;
+}
+
+static int ti_sci_clk_enable(struct clk *clk)
+{
+	struct ti_sci_clk_data *data = dev_get_priv(clk->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_clk_ops *cops = &sci->ops.clk_ops;
+	int ret;
+
+	debug("%s(clk=%p)\n", __func__, clk);
+
+	/*
+	 * Allow the System Controller to automatically manage the state of
+	 * this clock. If the device is enabled, then the clock is enabled.
+	 */
+	ret = cops->put_clock(sci, clk->id, clk->data);
+	if (ret)
+		dev_err(clk->dev, "%s: put_clock failed (%d)\n", __func__, ret);
+
+	return ret;
+}
+
+static int ti_sci_clk_disable(struct clk *clk)
+{
+	struct ti_sci_clk_data *data = dev_get_priv(clk->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_clk_ops *cops = &sci->ops.clk_ops;
+	int ret;
+
+	debug("%s(clk=%p)\n", __func__, clk);
+
+	/* Unconditionally disable clock, regardless of state of the device */
+	ret = cops->idle_clock(sci, clk->id, clk->data);
+	if (ret)
+		dev_err(clk->dev, "%s: idle_clock failed (%d)\n", __func__,
+			ret);
+
+	return ret;
+}
+
+static const struct udevice_id ti_sci_clk_of_match[] = {
+	{ .compatible = "ti,k2g-sci-clk" },
+	{ /* sentinel */ },
+};
+
+static struct clk_ops ti_sci_clk_ops = {
+	.of_xlate = ti_sci_clk_of_xlate,
+	.request = ti_sci_clk_request,
+	.free = ti_sci_clk_free,
+	.get_rate = ti_sci_clk_get_rate,
+	.set_rate = ti_sci_clk_set_rate,
+	.set_parent = ti_sci_clk_set_parent,
+	.enable = ti_sci_clk_enable,
+	.disable = ti_sci_clk_disable,
+};
+
+U_BOOT_DRIVER(ti_sci_clk) = {
+	.name = "ti-sci-clk",
+	.id = UCLASS_CLK,
+	.of_match = ti_sci_clk_of_match,
+	.probe = ti_sci_clk_probe,
+	.priv_auto_alloc_size = sizeof(struct ti_sci_clk_data),
+	.ops = &ti_sci_clk_ops,
+};