1/*
  2 * Texas Instrument's System Control Interface (TI-SCI) reset driver
  3 *
  4 * Copyright (C) 2015-2017 Texas Instruments Incorporated - https://www.ti.com/
  5 *	Andrew F. Davis <afd@ti.com>
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License version 2 as
  9 * published by the Free Software Foundation.
 10 *
 11 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
 12 * kind, whether express or implied; without even the implied warranty
 13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 14 * GNU General Public License for more details.
 15 */
 16
 17#include <linux/idr.h>
 18#include <linux/module.h>
 19#include <linux/mutex.h>
 20#include <linux/of.h>
 21#include <linux/platform_device.h>
 22#include <linux/reset-controller.h>
 23#include <linux/soc/ti/ti_sci_protocol.h>
 24
 25/**
 26 * struct ti_sci_reset_control - reset control structure
 27 * @dev_id: SoC-specific device identifier
 28 * @reset_mask: reset mask to use for toggling reset
 29 * @lock: synchronize reset_mask read-modify-writes
 30 */
 31struct ti_sci_reset_control {
 32	u32 dev_id;
 33	u32 reset_mask;
 34	struct mutex lock;
 35};
 36
 37/**
 38 * struct ti_sci_reset_data - reset controller information structure
 39 * @rcdev: reset controller entity
 40 * @dev: reset controller device pointer
 41 * @sci: TI SCI handle used for communication with system controller
 42 * @idr: idr structure for mapping ids to reset control structures
 43 */
 44struct ti_sci_reset_data {
 45	struct reset_controller_dev rcdev;
 46	struct device *dev;
 47	const struct ti_sci_handle *sci;
 48	struct idr idr;
 49};
 50
 51#define to_ti_sci_reset_data(p)	\
 52	container_of((p), struct ti_sci_reset_data, rcdev)
 53
 54/**
 55 * ti_sci_reset_set() - program a device's reset
 56 * @rcdev: reset controller entity
 57 * @id: ID of the reset to toggle
 58 * @assert: boolean flag to indicate assert or deassert
 59 *
 60 * This is a common internal function used to assert or deassert a device's
 61 * reset using the TI SCI protocol. The device's reset is asserted if the
 62 * @assert argument is true, or deasserted if @assert argument is false.
 63 * The mechanism itself is a read-modify-write procedure, the current device
 64 * reset register is read using a TI SCI device operation, the new value is
 65 * set or un-set using the reset's mask, and the new reset value written by
 66 * using another TI SCI device operation.
 67 *
 68 * Return: 0 for successful request, else a corresponding error value
 69 */
 70static int ti_sci_reset_set(struct reset_controller_dev *rcdev,
 71			    unsigned long id, bool assert)
 72{
 73	struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
 74	const struct ti_sci_handle *sci = data->sci;
 75	const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
 76	struct ti_sci_reset_control *control;
 77	u32 reset_state;
 78	int ret;
 79
 80	control = idr_find(&data->idr, id);
 81	if (!control)
 82		return -EINVAL;
 83
 84	mutex_lock(&control->lock);
 85
 86	ret = dev_ops->get_device_resets(sci, control->dev_id, &reset_state);
 87	if (ret)
 88		goto out;
 89
 90	if (assert)
 91		reset_state |= control->reset_mask;
 92	else
 93		reset_state &= ~control->reset_mask;
 94
 95	ret = dev_ops->set_device_resets(sci, control->dev_id, reset_state);
 96out:
 97	mutex_unlock(&control->lock);
 98
 99	return ret;
100}
101
102/**
103 * ti_sci_reset_assert() - assert device reset
104 * @rcdev: reset controller entity
105 * @id: ID of the reset to be asserted
106 *
107 * This function implements the reset driver op to assert a device's reset
108 * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
109 * with the corresponding parameters as passed in, but with the @assert
110 * argument set to true for asserting the reset.
111 *
112 * Return: 0 for successful request, else a corresponding error value
113 */
114static int ti_sci_reset_assert(struct reset_controller_dev *rcdev,
115			       unsigned long id)
116{
117	return ti_sci_reset_set(rcdev, id, true);
118}
119
120/**
121 * ti_sci_reset_deassert() - deassert device reset
122 * @rcdev: reset controller entity
123 * @id: ID of the reset to be deasserted
124 *
125 * This function implements the reset driver op to deassert a device's reset
126 * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
127 * with the corresponding parameters as passed in, but with the @assert
128 * argument set to false for deasserting the reset.
129 *
130 * Return: 0 for successful request, else a corresponding error value
131 */
132static int ti_sci_reset_deassert(struct reset_controller_dev *rcdev,
133				 unsigned long id)
134{
135	return ti_sci_reset_set(rcdev, id, false);
136}
137
138/**
139 * ti_sci_reset_status() - check device reset status
140 * @rcdev: reset controller entity
141 * @id: ID of reset to be checked
142 *
143 * This function implements the reset driver op to return the status of a
144 * device's reset using the TI SCI protocol. The reset register value is read
145 * by invoking the TI SCI device operation .get_device_resets(), and the
146 * status of the specific reset is extracted and returned using this reset's
147 * reset mask.
148 *
149 * Return: 0 if reset is deasserted, or a non-zero value if reset is asserted
150 */
151static int ti_sci_reset_status(struct reset_controller_dev *rcdev,
152			       unsigned long id)
153{
154	struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
155	const struct ti_sci_handle *sci = data->sci;
156	const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
157	struct ti_sci_reset_control *control;
158	u32 reset_state;
159	int ret;
160
161	control = idr_find(&data->idr, id);
162	if (!control)
163		return -EINVAL;
164
165	ret = dev_ops->get_device_resets(sci, control->dev_id, &reset_state);
166	if (ret)
167		return ret;
168
169	return reset_state & control->reset_mask;
170}
171
172static const struct reset_control_ops ti_sci_reset_ops = {
173	.assert		= ti_sci_reset_assert,
174	.deassert	= ti_sci_reset_deassert,
175	.status		= ti_sci_reset_status,
176};
177
178/**
179 * ti_sci_reset_of_xlate() - translate a set of OF arguments to a reset ID
180 * @rcdev: reset controller entity
181 * @reset_spec: OF reset argument specifier
182 *
183 * This function performs the translation of the reset argument specifier
184 * values defined in a reset consumer device node. The function allocates a
185 * reset control structure for that device reset, and will be used by the
186 * driver for performing any reset functions on that reset. An idr structure
187 * is allocated and used to map to the reset control structure. This idr
188 * is used by the driver to do reset lookups.
189 *
190 * Return: 0 for successful request, else a corresponding error value
191 */
192static int ti_sci_reset_of_xlate(struct reset_controller_dev *rcdev,
193				 const struct of_phandle_args *reset_spec)
194{
195	struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
196	struct ti_sci_reset_control *control;
197
198	if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
199		return -EINVAL;
200
201	control = devm_kzalloc(data->dev, sizeof(*control), GFP_KERNEL);
202	if (!control)
203		return -ENOMEM;
204
205	control->dev_id = reset_spec->args[0];
206	control->reset_mask = reset_spec->args[1];
207	mutex_init(&control->lock);
208
209	return idr_alloc(&data->idr, control, 0, 0, GFP_KERNEL);
210}
211
212static const struct of_device_id ti_sci_reset_of_match[] = {
213	{ .compatible = "ti,sci-reset", },
214	{ /* sentinel */ },
215};
216MODULE_DEVICE_TABLE(of, ti_sci_reset_of_match);
217
218static int ti_sci_reset_probe(struct platform_device *pdev)
219{
220	struct ti_sci_reset_data *data;
221
222	if (!pdev->dev.of_node)
223		return -ENODEV;
224
225	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
226	if (!data)
227		return -ENOMEM;
228
229	data->sci = devm_ti_sci_get_handle(&pdev->dev);
230	if (IS_ERR(data->sci))
231		return PTR_ERR(data->sci);
232
233	data->rcdev.ops = &ti_sci_reset_ops;
234	data->rcdev.owner = THIS_MODULE;
235	data->rcdev.of_node = pdev->dev.of_node;
236	data->rcdev.of_reset_n_cells = 2;
237	data->rcdev.of_xlate = ti_sci_reset_of_xlate;
238	data->dev = &pdev->dev;
239	idr_init(&data->idr);
240
241	platform_set_drvdata(pdev, data);
242
243	return reset_controller_register(&data->rcdev);
244}
245
246static int ti_sci_reset_remove(struct platform_device *pdev)
247{
248	struct ti_sci_reset_data *data = platform_get_drvdata(pdev);
249
250	reset_controller_unregister(&data->rcdev);
251
252	idr_destroy(&data->idr);
253
254	return 0;
255}
256
257static struct platform_driver ti_sci_reset_driver = {
258	.probe = ti_sci_reset_probe,
259	.remove = ti_sci_reset_remove,
260	.driver = {
261		.name = "ti-sci-reset",
262		.of_match_table = ti_sci_reset_of_match,
263	},
264};
265module_platform_driver(ti_sci_reset_driver);
266
267MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
268MODULE_DESCRIPTION("TI System Control Interface (TI SCI) Reset driver");
269MODULE_LICENSE("GPL v2");