1/*
2 * I2C multiplexer using a single register
3 *
4 * Copyright 2015 Freescale Semiconductor
5 * York Sun  <yorksun@freescale.com>
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the
9 * Free Software Foundation; either version 2 of the License, or (at your
10 * option) any later version.
11 */
12
13#include <linux/i2c.h>
14#include <linux/i2c-mux.h>
15#include <linux/init.h>
16#include <linux/io.h>
17#include <linux/module.h>
18#include <linux/of_address.h>
19#include <linux/platform_data/i2c-mux-reg.h>
20#include <linux/platform_device.h>
21#include <linux/slab.h>
22
23struct regmux {
24	struct i2c_adapter *parent;
25	struct i2c_adapter **adap; /* child busses */
26	struct i2c_mux_reg_platform_data data;
27};
28
29static int i2c_mux_reg_set(const struct regmux *mux, unsigned int chan_id)
30{
31	if (!mux->data.reg)
32		return -EINVAL;
33
34	/*
35	 * Write to the register, followed by a read to ensure the write is
36	 * completed on a "posted" bus, for example PCI or write buffers.
37	 * The endianness of reading doesn't matter and the return data
38	 * is not used.
39	 */
40	switch (mux->data.reg_size) {
41	case 4:
42		if (mux->data.little_endian)
43			iowrite32(chan_id, mux->data.reg);
44		else
45			iowrite32be(chan_id, mux->data.reg);
46		if (!mux->data.write_only)
47			ioread32(mux->data.reg);
48		break;
49	case 2:
50		if (mux->data.little_endian)
51			iowrite16(chan_id, mux->data.reg);
52		else
53			iowrite16be(chan_id, mux->data.reg);
54		if (!mux->data.write_only)
55			ioread16(mux->data.reg);
56		break;
57	case 1:
58		iowrite8(chan_id, mux->data.reg);
59		if (!mux->data.write_only)
60			ioread8(mux->data.reg);
61		break;
62	}
63
64	return 0;
65}
66
67static int i2c_mux_reg_select(struct i2c_adapter *adap, void *data,
68			      unsigned int chan)
69{
70	struct regmux *mux = data;
71
72	return i2c_mux_reg_set(mux, chan);
73}
74
75static int i2c_mux_reg_deselect(struct i2c_adapter *adap, void *data,
76				unsigned int chan)
77{
78	struct regmux *mux = data;
79
80	if (mux->data.idle_in_use)
81		return i2c_mux_reg_set(mux, mux->data.idle);
82
83	return 0;
84}
85
86#ifdef CONFIG_OF
87static int i2c_mux_reg_probe_dt(struct regmux *mux,
88					struct platform_device *pdev)
89{
90	struct device_node *np = pdev->dev.of_node;
91	struct device_node *adapter_np, *child;
92	struct i2c_adapter *adapter;
93	struct resource res;
94	unsigned *values;
95	int i = 0;
96
97	if (!np)
98		return -ENODEV;
99
100	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
101	if (!adapter_np) {
102		dev_err(&pdev->dev, "Cannot parse i2c-parent\n");
103		return -ENODEV;
104	}
105	adapter = of_find_i2c_adapter_by_node(adapter_np);
106	of_node_put(adapter_np);
107	if (!adapter)
108		return -EPROBE_DEFER;
109
110	mux->parent = adapter;
111	mux->data.parent = i2c_adapter_id(adapter);
112	put_device(&adapter->dev);
113
114	mux->data.n_values = of_get_child_count(np);
115	if (of_find_property(np, "little-endian", NULL)) {
116		mux->data.little_endian = true;
117	} else if (of_find_property(np, "big-endian", NULL)) {
118		mux->data.little_endian = false;
119	} else {
120#if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : \
121	defined(__LITTLE_ENDIAN)
122		mux->data.little_endian = true;
123#elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : \
124	defined(__BIG_ENDIAN)
125		mux->data.little_endian = false;
126#else
127#error Endianness not defined?
128#endif
129	}
130	if (of_find_property(np, "write-only", NULL))
131		mux->data.write_only = true;
132	else
133		mux->data.write_only = false;
134
135	values = devm_kzalloc(&pdev->dev,
136			      sizeof(*mux->data.values) * mux->data.n_values,
137			      GFP_KERNEL);
138	if (!values) {
139		dev_err(&pdev->dev, "Cannot allocate values array");
140		return -ENOMEM;
141	}
142
143	for_each_child_of_node(np, child) {
144		of_property_read_u32(child, "reg", values + i);
145		i++;
146	}
147	mux->data.values = values;
148
149	if (!of_property_read_u32(np, "idle-state", &mux->data.idle))
150		mux->data.idle_in_use = true;
151
152	/* map address from "reg" if exists */
153	if (of_address_to_resource(np, 0, &res)) {
154		mux->data.reg_size = resource_size(&res);
155		mux->data.reg = devm_ioremap_resource(&pdev->dev, &res);
156		if (IS_ERR(mux->data.reg))
157			return PTR_ERR(mux->data.reg);
158	}
159
160	return 0;
161}
162#else
163static int i2c_mux_reg_probe_dt(struct regmux *mux,
164					struct platform_device *pdev)
165{
166	return 0;
167}
168#endif
169
170static int i2c_mux_reg_probe(struct platform_device *pdev)
171{
172	struct regmux *mux;
173	struct i2c_adapter *parent;
174	struct resource *res;
175	int (*deselect)(struct i2c_adapter *, void *, u32);
176	unsigned int class;
177	int i, ret, nr;
178
179	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
180	if (!mux)
181		return -ENOMEM;
182
183	platform_set_drvdata(pdev, mux);
184
185	if (dev_get_platdata(&pdev->dev)) {
186		memcpy(&mux->data, dev_get_platdata(&pdev->dev),
187			sizeof(mux->data));
188
189		parent = i2c_get_adapter(mux->data.parent);
190		if (!parent)
191			return -EPROBE_DEFER;
192
193		mux->parent = parent;
194	} else {
195		ret = i2c_mux_reg_probe_dt(mux, pdev);
196		if (ret < 0) {
197			dev_err(&pdev->dev, "Error parsing device tree");
198			return ret;
199		}
200	}
201
202	if (!mux->data.reg) {
203		dev_info(&pdev->dev,
204			"Register not set, using platform resource\n");
205		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
206		mux->data.reg_size = resource_size(res);
207		mux->data.reg = devm_ioremap_resource(&pdev->dev, res);
208		if (IS_ERR(mux->data.reg))
209			return PTR_ERR(mux->data.reg);
210	}
211
212	if (mux->data.reg_size != 4 && mux->data.reg_size != 2 &&
213	    mux->data.reg_size != 1) {
214		dev_err(&pdev->dev, "Invalid register size\n");
215		return -EINVAL;
216	}
217
218	mux->adap = devm_kzalloc(&pdev->dev,
219				 sizeof(*mux->adap) * mux->data.n_values,
220				 GFP_KERNEL);
221	if (!mux->adap) {
222		dev_err(&pdev->dev, "Cannot allocate i2c_adapter structure");
223		return -ENOMEM;
224	}
225
226	if (mux->data.idle_in_use)
227		deselect = i2c_mux_reg_deselect;
228	else
229		deselect = NULL;
230
231	for (i = 0; i < mux->data.n_values; i++) {
232		nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;
233		class = mux->data.classes ? mux->data.classes[i] : 0;
234
235		mux->adap[i] = i2c_add_mux_adapter(mux->parent, &pdev->dev, mux,
236						   nr, mux->data.values[i],
237						   class, i2c_mux_reg_select,
238						   deselect);
239		if (!mux->adap[i]) {
240			ret = -ENODEV;
241			dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
242			goto add_adapter_failed;
243		}
244	}
245
246	dev_dbg(&pdev->dev, "%d port mux on %s adapter\n",
247		 mux->data.n_values, mux->parent->name);
248
249	return 0;
250
251add_adapter_failed:
252	for (; i > 0; i--)
253		i2c_del_mux_adapter(mux->adap[i - 1]);
254
255	return ret;
256}
257
258static int i2c_mux_reg_remove(struct platform_device *pdev)
259{
260	struct regmux *mux = platform_get_drvdata(pdev);
261	int i;
262
263	for (i = 0; i < mux->data.n_values; i++)
264		i2c_del_mux_adapter(mux->adap[i]);
265
266	i2c_put_adapter(mux->parent);
267
268	return 0;
269}
270
271static const struct of_device_id i2c_mux_reg_of_match[] = {
272	{ .compatible = "i2c-mux-reg", },
273	{},
274};
275MODULE_DEVICE_TABLE(of, i2c_mux_reg_of_match);
276
277static struct platform_driver i2c_mux_reg_driver = {
278	.probe	= i2c_mux_reg_probe,
279	.remove	= i2c_mux_reg_remove,
280	.driver	= {
281		.name	= "i2c-mux-reg",
282	},
283};
284
285module_platform_driver(i2c_mux_reg_driver);
286
287MODULE_DESCRIPTION("Register-based I2C multiplexer driver");
288MODULE_AUTHOR("York Sun <yorksun@freescale.com>");
289MODULE_LICENSE("GPL");
290MODULE_ALIAS("platform:i2c-mux-reg");
291