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[PATCH v2 0/2] Add support for SYSCON reset

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  [PATCH v2 0/2] Add support for SYSCON reset "Andrew F. Davis" <afd@ti.com> - 2016-03-10 22:50 +0100
    [PATCH v2 1/2] Documentation: dt: reset: Add syscon reset binding "Andrew F. Davis" <afd@ti.com> - 2016-03-10 22:50 +0100
    [PATCH v2 2/2] reset: add a SYSCON based reset driver "Andrew F. Davis" <afd@ti.com> - 2016-03-10 22:50 +0100

#1355417 — [PATCH v2 0/2] Add support for SYSCON reset

Some SoCs contain reset controls for modules that are memory-mapped to
areas shared with other module configuration settings. This requires
synchronization across all drivers accessing this memory area. This
series adds a generic SYSCON reset driver to allow resets toggled
by bits in memory-mapped registers through SYSCON.

Changes from v1:
 - Reset control information is now described in the reset node, this
   keeps the reset information centralized for easy verification
 - Other small fixups

Andrew F. Davis (2):
  Documentation: dt: reset: Add syscon reset binding
  reset: add a SYSCON based reset driver

 .../devicetree/bindings/reset/syscon-reset.txt     | 114 +++++++++
 drivers/reset/Kconfig                              |  10 +
 drivers/reset/Makefile                             |   1 +
 drivers/reset/reset-syscon.c                       | 283 +++++++++++++++++++++
 include/dt-bindings/reset/syscon.h                 |  23 ++
 5 files changed, 431 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/reset/syscon-reset.txt
 create mode 100644 drivers/reset/reset-syscon.c
 create mode 100644 include/dt-bindings/reset/syscon.h

-- 
2.7.2

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#1355418 — [PATCH v2 1/2] Documentation: dt: reset: Add syscon reset binding

Add syscon reset controller binding. This will hook to the reset
framework and use syscon/regmap to set reset bits. This allows
reset control of individual SoC subsytems and devices with
memory-mapped reset registers in a common register memory
space.

Signed-off-by: Andrew F. Davis <afd@ti.com>
[s-anna@ti.com: revise the binding format]
Signed-off-by: Suman Anna <s-anna@ti.com>
---
 .../devicetree/bindings/reset/syscon-reset.txt     | 114 +++++++++++++++++++++
 include/dt-bindings/reset/syscon.h                 |  23 +++++
 2 files changed, 137 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/reset/syscon-reset.txt
 create mode 100644 include/dt-bindings/reset/syscon.h

diff --git a/Documentation/devicetree/bindings/reset/syscon-reset.txt b/Documentation/devicetree/bindings/reset/syscon-reset.txt
new file mode 100644
index 0000000..02bc9e3
--- /dev/null
+++ b/Documentation/devicetree/bindings/reset/syscon-reset.txt
@@ -0,0 +1,114 @@
+SysCon Reset Controller
+=======================
+
+Almost all SoCs have hardware modules that require reset control in addition
+to clock and power control for their functionality. The reset control is
+typically provided by means of memory-mapped I/O registers. These registers are
+sometimes a part of a larger register space region implementing various
+functionalities. This register range is best represented as a syscon node to
+allow multiple entities to access their relevant registers in the common
+register space.
+
+A SysCon Reset Controller node defines a device that uses a syscon node
+and provides reset management functionality for various hardware modules
+present on the SoC.
+
+SysCon Reset Controller Node
+============================
+Each of the reset provider/controller nodes should be a child of a syscon
+node and have the following properties.
+
+Required properties:
+--------------------
+ - compatible		: Should be "syscon-reset"
+ - #reset-cells		: Should be 1. Please see the reset consumer node below
+			  for usage details
+ - #address-cells	: Should be 1
+ - #size-cells		: Should be 0
+
+SysCon Reset Child Node
+============================
+Each reset provider/controller node should have a child node for each reset
+it would like to expose to consumers.
+
+Required properties:
+--------------------
+ - reg			: This reset's number, this will be used to reference
+			  this reset by consumers of this reset
+ - reset-control	: Contains the reset control register information
+			  Should contain 3 cells defined as:
+			    Cell #1 : register offset of the reset
+			              control/status register from the syscon
+			              register base
+			    Cell #2 : bit shift value for the reset in the
+			              respective reset control/status register
+			    Cell #3 : polarity of the reset bit. Should be 1 or
+				      RESET_ASSERT_SET for resets that are
+				      asserted when the bit is set, 0 or
+				      RESET_ASSERT_CLEAR for resets that are
+				      asserted when the bit is cleared
+
+Optional properties:
+--------------------
+ - reset-status		: Contains the reset status register information. The
+			  contents of this property are the equivalent to
+			  reset-control as defined above. If this property is
+			  not present and the toggle flag is not set, the
+			  reset register is assumed to be the same as the
+			  control register
+ - toggle		: Mark this reset as a toggle only reset, this is used
+			  when no status register is available.
+
+SysCon Reset Consumer Nodes
+===========================
+Each of the reset consumer nodes should have the following properties,
+in addition to their own properties.
+
+Required properties:
+--------------------
+ - resets	: A phandle and a reset specifier, the reset specifier should
+		  be a numerical address matching the desired reset as set
+		  by the reg property defined above.
+
+Please also refer to Documentation/devicetree/bindings/reset/reset.txt for
+common reset controller usage by consumers.
+
+Example:
+--------
+The following example demonstrates a syscon node, the reset controller node
+using the syscon node, and a consumer (a DSP device) on the TI Keystone 2
+Hawking SoC.
+
+/ {
+	soc {
+		psc: power-sleep-controller@02350000 {
+			compatible = "syscon", "simple-mfd";
+			reg = <0x02350000 0x1000>;
+
+			pscrst: psc-reset {
+				compatible = "syscon-reset";
+				#reset-cells = <1>;
+				#address-cells = <1>;
+				#size-cells = <0>;
+
+				dsp@0 {
+					reg = <0>;
+					reset-control = <0xa3c 8 RESET_ASSERT_CLEAR>;
+					reset-status = <0x83c 8 RESET_ASSERT_CLEAR>;
+				};
+
+				imu@1 {
+					reg = <1>;
+					reset-control = <0xa40 5 RESET_ASSERT_SET>;
+					toggle;
+				};
+			};
+		};
+
+		dsp0: dsp0 {
+			...
+			resets = <&pscrst 0>;
+			...
+		};
+	};
+};
diff --git a/include/dt-bindings/reset/syscon.h b/include/dt-bindings/reset/syscon.h
new file mode 100644
index 0000000..9927779
--- /dev/null
+++ b/include/dt-bindings/reset/syscon.h
@@ -0,0 +1,23 @@
+/*
+ * Syscon Reset definitions
+ *
+ * Copyright (C) 2015-2016 Texas Instruments Incorporated - http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __DT_BINDINGS_RESET_SYSCON_H__
+#define __DT_BINDINGS_RESET_SYSCON_H__
+
+#define RESET_ASSERT_CLEAR	0x0
+#define RESET_ASSERT_SET	0x1
+
+#endif
-- 
2.7.2

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#1355420 — [PATCH v2 2/2] reset: add a SYSCON based reset driver

Add a reset-controller driver for performing reset management of
various devices present on the SoC, with the reset registers shared
between devices in a common register memory space. This driver uses
the syscon/regmap frameworks to actually implement the various reset
functionalities needed by the reset consumer devices.

Signed-off-by: Andrew F. Davis <afd@ti.com>
[s-anna@ti.com: add documentation, syscon name change]
Signed-off-by: Suman Anna <s-anna@ti.com>
---
 drivers/reset/Kconfig        |  10 ++
 drivers/reset/Makefile       |   1 +
 drivers/reset/reset-syscon.c | 283 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 294 insertions(+)
 create mode 100644 drivers/reset/reset-syscon.c

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index df37212..5f26755 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -12,5 +12,15 @@ menuconfig RESET_CONTROLLER
 
 	  If unsure, say no.
 
+config SYSCON_RESET
+	tristate "SYSCON Reset Driver"
+	depends on RESET_CONTROLLER
+	select MFD_SYSCON
+	help
+	  This enables the reset driver support for devices with memory-mapped
+	  reset registers as part of a syscon device node. If you wish to use
+	  the reset framework for such memory-mapped devices, say Y here.
+	  Otherwise, say N.
+
 source "drivers/reset/sti/Kconfig"
 source "drivers/reset/hisilicon/Kconfig"
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 4d7178e..6b3f6e3 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_ARCH_STI) += sti/
 obj-$(CONFIG_ARCH_HISI) += hisilicon/
 obj-$(CONFIG_ARCH_ZYNQ) += reset-zynq.o
 obj-$(CONFIG_ATH79) += reset-ath79.o
+obj-$(CONFIG_SYSCON_RESET) += reset-syscon.o
diff --git a/drivers/reset/reset-syscon.c b/drivers/reset/reset-syscon.c
new file mode 100644
index 0000000..d127c83
--- /dev/null
+++ b/drivers/reset/reset-syscon.c
@@ -0,0 +1,283 @@
+/*
+ * SYSCON regmap reset driver
+ *
+ * Copyright (C) 2015-2016 Texas Instruments Incorporated - http://www.ti.com/
+ *	Andrew F. Davis <afd@ti.com>
+ *	Suman Anna <afd@ti.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+
+/**
+ * struct syscon_reset_control - reset control structure
+ * @offset: reset control register offset from syscon base
+ * @reset_bit: reset bit in the reset control register
+ * @assert_high: flag to indicate if setting the bit high asserts the reset
+ * @status_offset: reset status register offset from syscon base
+ * @status_reset_bit: reset status bit in the reset status register
+ * @status_assert_high: flag to indicate if a set bit represents asserted state
+ * @toggle: flag to indicate this reset has no readable status register
+ */
+struct syscon_reset_control {
+	unsigned int offset;
+	unsigned int reset_bit;
+	bool assert_high;
+	unsigned int status_offset;
+	unsigned int status_reset_bit;
+	bool status_assert_high;
+	bool toggle;
+};
+
+/**
+ * struct syscon_reset_data - reset controller information structure
+ * @rcdev: reset controller entity
+ * @dev: reset controller device pointer
+ * @memory: regmap handle containing the memory-mapped reset registers
+ * @idr: idr structure for mapping ids to reset control structures
+ */
+struct syscon_reset_data {
+	struct reset_controller_dev rcdev;
+	struct device *dev;
+	struct regmap *memory;
+};
+
+#define to_syscon_reset_data(rcdev)	\
+	container_of(rcdev, struct syscon_reset_data, rcdev)
+
+/**
+ * syscon_reset_get_control() - get reset control info from DT node
+ * @data: reset controller data
+ * @id: ID address of control data node
+ * @control: control data struct to fill
+ *
+ * Search DT for a child node at the specified address that contains
+ * reset control info and use that to fill in control data.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int syscon_reset_get_control(struct syscon_reset_data *data,
+				    unsigned long id,
+				    struct syscon_reset_control *control)
+{
+	struct device_node *child;
+	const __be32 *address;
+	const __be32 *list;
+	int size;
+
+	for_each_child_of_node(data->rcdev.of_node, child) {
+		address = of_get_address(child, 0, NULL, NULL);
+		if (!address || be32_to_cpup(address) != id)
+			continue;
+
+		list = of_get_property(child, "reset-control", &size);
+		if (!list || size != (3 * sizeof(*list)))
+			return -EINVAL;
+		control->offset = be32_to_cpup(list++);
+		control->reset_bit = be32_to_cpup(list++);
+		control->assert_high = be32_to_cpup(list) == 1;
+
+		if (of_find_property(child, "reset-toggle", NULL)) {
+			control->toggle = true;
+			return 0;
+		}
+		control->toggle = false;
+
+		list = of_get_property(child, "reset-status", &size);
+		if (!list) {
+			/* use control register values */
+			control->status_offset = control->offset;
+			control->status_reset_bit = control->reset_bit;
+			control->status_assert_high = control->assert_high;
+			return 0;
+		}
+
+		if (size != (3 * sizeof(*list)))
+			return -EINVAL;
+		control->status_offset = be32_to_cpup(list++);
+		control->status_reset_bit = be32_to_cpup(list++);
+		control->status_assert_high = be32_to_cpup(list) == 1;
+		return 0;
+	}
+
+	return -ENOENT;
+}
+
+/**
+ * syscon_reset_set() - program a device's reset
+ * @rcdev: reset controller entity
+ * @id: ID of the reset to toggle
+ * @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 regmap API. The device's reset is asserted if the @assert
+ * argument is true, or deasserted if the @assert argument is false.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int syscon_reset_set(struct reset_controller_dev *rcdev,
+			    unsigned long id, bool assert)
+{
+	struct syscon_reset_data *data = to_syscon_reset_data(rcdev);
+	struct syscon_reset_control control;
+	unsigned int mask, value;
+	int ret;
+
+	ret = syscon_reset_get_control(data, id, &control);
+	if (ret)
+		return ret;
+
+	mask = BIT(control.reset_bit);
+	value = (assert == control.assert_high) ? mask : 0x0;
+
+	return regmap_update_bits(data->memory, control.offset, mask, value);
+}
+
+/**
+ * syscon_reset_assert() - assert device reset
+ * @rcdev: reset controller entity
+ * @id: ID of the reset to be asserted
+ *
+ * This function implements the reset driver op to assert a device's reset.
+ * This invokes the function syscon_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 syscon_reset_assert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	return syscon_reset_set(rcdev, id, true);
+}
+
+/**
+ * syscon_reset_deassert() - deassert device reset
+ * @rcdev: reset controller entity
+ * @id: ID of reset to be deasserted
+ *
+ * This function implements the reset driver op to deassert a device's reset.
+ * This invokes the function syscon_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 syscon_reset_deassert(struct reset_controller_dev *rcdev,
+				 unsigned long id)
+{
+	return syscon_reset_set(rcdev, id, false);
+}
+
+/**
+ * syscon_reset_status() - check device reset status
+ * @rcdev: reset controller entity
+ * @id: ID of the reset for which the status is being requested
+ *
+ * This function implements the reset driver op to return the status of a
+ * device's reset.
+ *
+ * Return: 0 if reset is deasserted, true if reset is asserted, else a
+ * corresponding error value
+ */
+static int syscon_reset_status(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	struct syscon_reset_data *data = to_syscon_reset_data(rcdev);
+	struct syscon_reset_control control;
+	unsigned int reset_state;
+	int ret;
+
+	ret = syscon_reset_get_control(data, id, &control);
+	if (ret)
+		return ret;
+
+	if (control.toggle)
+		return -ENOSYS; /* status not supported for this reset */
+
+	ret = regmap_read(data->memory, control.status_offset, &reset_state);
+	if (ret)
+		return ret;
+
+	return (reset_state & BIT(control.status_reset_bit)) ==
+			control.status_assert_high;
+}
+
+static struct reset_control_ops syscon_reset_ops = {
+	.assert		= syscon_reset_assert,
+	.deassert	= syscon_reset_deassert,
+	.status		= syscon_reset_status,
+};
+
+static int syscon_reset_probe(struct platform_device *pdev)
+{
+	struct syscon_reset_data *data;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct regmap *memory;
+
+	if (!np)
+		return -ENODEV;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	memory = syscon_node_to_regmap(np->parent);
+	if (IS_ERR(memory))
+		return PTR_ERR(memory);
+
+	data->rcdev.ops = &syscon_reset_ops;
+	data->rcdev.owner = THIS_MODULE;
+	data->rcdev.of_node = np;
+	data->rcdev.nr_resets = of_get_child_count(np);
+	data->dev = dev;
+	data->memory = memory;
+	platform_set_drvdata(pdev, data);
+
+	return reset_controller_register(&data->rcdev);
+}
+
+static int syscon_reset_remove(struct platform_device *pdev)
+{
+	struct syscon_reset_data *data = platform_get_drvdata(pdev);
+
+	reset_controller_unregister(&data->rcdev);
+
+	return 0;
+}
+
+static const struct of_device_id syscon_reset_of_match[] = {
+	{ .compatible = "syscon-reset", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, syscon_reset_of_match);
+
+static struct platform_driver syscon_reset_driver = {
+	.probe = syscon_reset_probe,
+	.remove = syscon_reset_remove,
+	.driver = {
+		.name = "syscon-reset",
+		.of_match_table = syscon_reset_of_match,
+	},
+};
+module_platform_driver(syscon_reset_driver);
+
+MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
+MODULE_AUTHOR("Suman Anna <s-anna@ti.com>");
+MODULE_DESCRIPTION("SYSCON Regmap Reset Driver");
+MODULE_LICENSE("GPL v2");
-- 
2.7.2

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