reset: Introduce TI System Control Interface (TI SCI) reset 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 reset driver that communicates to the system
controller over the TI SCI protocol for performing reset management of
various devices present on the SoC. Various reset functionalities are
achieved by the means of different TI SCI device operations provided by
the TI SCI framework.

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

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

doc/device-tree-bindings/reset/ti,sci-reset.txt

@@ -0,0 +1,54 @@
+Texas Instruments TI SCI Reset Controller
+=========================================
+
+Some TI SoCs contain a system controller (like the SYSFW, etc...) that is
+responsible for controlling the state of the IPs that are present.
+Communication between the host processor running an OS and the system
+controller happens through a protocol known as TI SCI [1].
+
+[1] http://processors.wiki.ti.com/index.php/TISCI
+
+Reset Controller Node
+=====================
+The reset controller node represents the resets of various hardware modules
+present on the SoC 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,sci-reset"
+ - #reset-cells: Must be 2. Please see the reset consumer node below for
+		 usage details.
+
+Example (AM65x):
+----------------
+	sysfw: sysfw {
+		compatible = "ti,am654-system-controller";
+		...
+		k3_reset: reset-controller {
+			compatible = "ti,sci-reset";
+			#reset-cells = <2>;
+		};
+	};
+
+Reset Consumers
+===============
+Each of the reset consumer nodes should have the following properties,
+in addition to their own properties.
+
+Required Properties:
+--------------------
+ - resets: A phandle and reset specifier pair, one pair for each reset signal
+	   that affects the device, or that the device manages. The phandle
+	   should point to the TI SCI reset controller node, and the reset
+	   specifier should have 2 cell-values. The first cell should contain
+	   the device ID. The second cell should contain the reset mask value
+	   used by system controller.
+
+Example (AM65x):
+----------------
+	uart2: serial@02800000 {
+		compatible = "ti,omap4-uart";
+		...
+		resets = <&k3_reset 5 1>;
+	};

drivers/reset/Kconfig

@@ -49,6 +49,14 @@ config TEGRA186_RESET
 	  Enable support for manipulating Tegra's on-SoC reset signals via IPC
 	  requests to the BPMP (Boot and Power Management Processor).
 
+config RESET_TI_SCI
+	bool "TI System Control Interface (TI SCI) reset driver"
+	depends on DM_RESET && TI_SCI_PROTOCOL
+	help
+	  This enables the reset driver support over TI System Control Interface
+	  available on some new TI's SoCs. If you wish to use reset resources
+	  managed by the TI System Controller, say Y here. Otherwise, say N.
+
 config RESET_BCM6345
 	bool "Reset controller driver for BCM6345"
 	depends on DM_RESET && ARCH_BMIPS

drivers/reset/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_STI_RESET) += sti-reset.o
 obj-$(CONFIG_STM32_RESET) += stm32-reset.o
 obj-$(CONFIG_TEGRA_CAR_RESET) += tegra-car-reset.o
 obj-$(CONFIG_TEGRA186_RESET) += tegra186-reset.o
+obj-$(CONFIG_RESET_TI_SCI) += reset-ti-sci.o
 obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
 obj-$(CONFIG_RESET_UNIPHIER) += reset-uniphier.o
 obj-$(CONFIG_AST2500_RESET) += ast2500-reset.o

drivers/reset/reset-ti-sci.c

@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Texas Instruments System Control Interface (TI SCI) reset driver
+ *
+ * Copyright (C) 2018 Texas Instruments Incorporated - http://www.ti.com/
+ *	Andreas Dannenberg <dannenberg@ti.com>
+ *
+ * Loosely based on Linux kernel reset-ti-sci.c...
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <reset-uclass.h>
+#include <linux/soc/ti/ti_sci_protocol.h>
+
+/**
+ * struct ti_sci_reset_data - reset controller information structure
+ * @sci: TI SCI handle used for communication with system controller
+ */
+struct ti_sci_reset_data {
+	const struct ti_sci_handle *sci;
+};
+
+static int ti_sci_reset_probe(struct udevice *dev)
+{
+	struct ti_sci_reset_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_reset_of_xlate(struct reset_ctl *rst,
+				 struct ofnode_phandle_args *args)
+{
+	debug("%s(rst=%p, args_count=%d)\n", __func__, rst, 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 reset provider id field is used as a
+	 * device ID, and the data field is used as the associated reset mask.
+	 */
+	rst->id = args->args[0];
+	rst->data = args->args[1];
+
+	return 0;
+}
+
+static int ti_sci_reset_request(struct reset_ctl *rst)
+{
+	debug("%s(rst=%p)\n", __func__, rst);
+	return 0;
+}
+
+static int ti_sci_reset_free(struct reset_ctl *rst)
+{
+	debug("%s(rst=%p)\n", __func__, rst);
+	return 0;
+}
+
+/**
+ * ti_sci_reset_set() - program a device's reset
+ * @rst: Handle to a single reset signal
+ * @assert: boolean flag to indicate assert or deassert
+ *
+ * This is a common internal function used to assert or deassert a device's
+ * reset using the TI SCI protocol. The device's reset is asserted if the
+ * @assert argument is true, or deasserted if @assert argument is false.
+ * The mechanism itself is a read-modify-write procedure, the current device
+ * reset register is read using a TI SCI device operation, the new value is
+ * set or un-set using the reset's mask, and the new reset value written by
+ * using another TI SCI device operation.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int ti_sci_reset_set(struct reset_ctl *rst, bool assert)
+{
+	struct ti_sci_reset_data *data = dev_get_priv(rst->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_dev_ops *dops = &sci->ops.dev_ops;
+	u32 reset_state;
+	int ret;
+
+	ret = dops->get_device_resets(sci, rst->id, &reset_state);
+	if (ret) {
+		dev_err(rst->dev, "%s: get_device_resets failed (%d)\n",
+			__func__, ret);
+		return ret;
+	}
+
+	if (assert)
+		reset_state |= rst->data;
+	else
+		reset_state &= ~rst->data;
+
+	ret = dops->set_device_resets(sci, rst->id, reset_state);
+	if (ret) {
+		dev_err(rst->dev, "%s: set_device_resets failed (%d)\n",
+			__func__, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * ti_sci_reset_assert() - assert device reset
+ * @rst: Handle to a single reset signal
+ *
+ * This function implements the reset driver op to assert a device's reset
+ * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
+ * with the corresponding parameters as passed in, but with the @assert
+ * argument set to true for asserting the reset.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int ti_sci_reset_assert(struct reset_ctl *rst)
+{
+	debug("%s(rst=%p)\n", __func__, rst);
+	return ti_sci_reset_set(rst, true);
+}
+
+/**
+ * ti_sci_reset_deassert() - deassert device reset
+ * @rst: Handle to a single reset signal
+ *
+ * This function implements the reset driver op to deassert a device's reset
+ * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
+ * with the corresponding parameters as passed in, but with the @assert
+ * argument set to false for deasserting the reset.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int ti_sci_reset_deassert(struct reset_ctl *rst)
+{
+	debug("%s(rst=%p)\n", __func__, rst);
+	return ti_sci_reset_set(rst, false);
+}
+
+/**
+ * ti_sci_reset_status() - check device reset status
+ * @rst: Handle to a single reset signal
+ *
+ * This function implements the reset driver op to return the status of a
+ * device's reset using the TI SCI protocol. The reset register value is read
+ * by invoking the TI SCI device operation .get_device_resets(), and the
+ * status of the specific reset is extracted and returned using this reset's
+ * reset mask.
+ *
+ * Return: 0 if reset is deasserted, or a non-zero value if reset is asserted
+ */
+static int ti_sci_reset_status(struct reset_ctl *rst)
+{
+	struct ti_sci_reset_data *data = dev_get_priv(rst->dev);
+	const struct ti_sci_handle *sci = data->sci;
+	const struct ti_sci_dev_ops *dops = &sci->ops.dev_ops;
+	u32 reset_state;
+	int ret;
+
+	debug("%s(rst=%p)\n", __func__, rst);
+
+	ret = dops->get_device_resets(sci, rst->id, &reset_state);
+	if (ret) {
+		dev_err(rst->dev, "%s: get_device_resets failed (%d)\n",
+			__func__, ret);
+		return ret;
+	}
+
+	return reset_state & rst->data;
+}
+
+static const struct udevice_id ti_sci_reset_of_match[] = {
+	{ .compatible = "ti,sci-reset", },
+	{ /* sentinel */ },
+};
+
+static struct reset_ops ti_sci_reset_ops = {
+	.of_xlate = ti_sci_reset_of_xlate,
+	.request = ti_sci_reset_request,
+	.free = ti_sci_reset_free,
+	.rst_assert = ti_sci_reset_assert,
+	.rst_deassert = ti_sci_reset_deassert,
+	.rst_status = ti_sci_reset_status,
+};
+
+U_BOOT_DRIVER(ti_sci_reset) = {
+	.name = "ti-sci-reset",
+	.id = UCLASS_RESET,
+	.of_match = ti_sci_reset_of_match,
+	.probe = ti_sci_reset_probe,
+	.priv_auto_alloc_size = sizeof(struct ti_sci_reset_data),
+	.ops = &ti_sci_reset_ops,
+};