xref: /openbmc/linux/drivers/i2c/muxes/i2c-mux-reg.c (revision 68198dca)
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 
23 struct regmux {
24 	struct i2c_mux_reg_platform_data data;
25 };
26 
27 static int i2c_mux_reg_set(const struct regmux *mux, unsigned int chan_id)
28 {
29 	if (!mux->data.reg)
30 		return -EINVAL;
31 
32 	/*
33 	 * Write to the register, followed by a read to ensure the write is
34 	 * completed on a "posted" bus, for example PCI or write buffers.
35 	 * The endianness of reading doesn't matter and the return data
36 	 * is not used.
37 	 */
38 	switch (mux->data.reg_size) {
39 	case 4:
40 		if (mux->data.little_endian)
41 			iowrite32(chan_id, mux->data.reg);
42 		else
43 			iowrite32be(chan_id, mux->data.reg);
44 		if (!mux->data.write_only)
45 			ioread32(mux->data.reg);
46 		break;
47 	case 2:
48 		if (mux->data.little_endian)
49 			iowrite16(chan_id, mux->data.reg);
50 		else
51 			iowrite16be(chan_id, mux->data.reg);
52 		if (!mux->data.write_only)
53 			ioread16(mux->data.reg);
54 		break;
55 	case 1:
56 		iowrite8(chan_id, mux->data.reg);
57 		if (!mux->data.write_only)
58 			ioread8(mux->data.reg);
59 		break;
60 	}
61 
62 	return 0;
63 }
64 
65 static int i2c_mux_reg_select(struct i2c_mux_core *muxc, u32 chan)
66 {
67 	struct regmux *mux = i2c_mux_priv(muxc);
68 
69 	return i2c_mux_reg_set(mux, chan);
70 }
71 
72 static int i2c_mux_reg_deselect(struct i2c_mux_core *muxc, u32 chan)
73 {
74 	struct regmux *mux = i2c_mux_priv(muxc);
75 
76 	if (mux->data.idle_in_use)
77 		return i2c_mux_reg_set(mux, mux->data.idle);
78 
79 	return 0;
80 }
81 
82 #ifdef CONFIG_OF
83 static int i2c_mux_reg_probe_dt(struct regmux *mux,
84 				struct platform_device *pdev)
85 {
86 	struct device_node *np = pdev->dev.of_node;
87 	struct device_node *adapter_np, *child;
88 	struct i2c_adapter *adapter;
89 	struct resource res;
90 	unsigned *values;
91 	int i = 0;
92 
93 	if (!np)
94 		return -ENODEV;
95 
96 	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
97 	if (!adapter_np) {
98 		dev_err(&pdev->dev, "Cannot parse i2c-parent\n");
99 		return -ENODEV;
100 	}
101 	adapter = of_find_i2c_adapter_by_node(adapter_np);
102 	of_node_put(adapter_np);
103 	if (!adapter)
104 		return -EPROBE_DEFER;
105 
106 	mux->data.parent = i2c_adapter_id(adapter);
107 	put_device(&adapter->dev);
108 
109 	mux->data.n_values = of_get_child_count(np);
110 	if (of_property_read_bool(np, "little-endian")) {
111 		mux->data.little_endian = true;
112 	} else if (of_property_read_bool(np, "big-endian")) {
113 		mux->data.little_endian = false;
114 	} else {
115 #if defined(__BYTE_ORDER) ? __BYTE_ORDER == __LITTLE_ENDIAN : \
116 	defined(__LITTLE_ENDIAN)
117 		mux->data.little_endian = true;
118 #elif defined(__BYTE_ORDER) ? __BYTE_ORDER == __BIG_ENDIAN : \
119 	defined(__BIG_ENDIAN)
120 		mux->data.little_endian = false;
121 #else
122 #error Endianness not defined?
123 #endif
124 	}
125 	mux->data.write_only = of_property_read_bool(np, "write-only");
126 
127 	values = devm_kzalloc(&pdev->dev,
128 			      sizeof(*mux->data.values) * mux->data.n_values,
129 			      GFP_KERNEL);
130 	if (!values) {
131 		dev_err(&pdev->dev, "Cannot allocate values array");
132 		return -ENOMEM;
133 	}
134 
135 	for_each_child_of_node(np, child) {
136 		of_property_read_u32(child, "reg", values + i);
137 		i++;
138 	}
139 	mux->data.values = values;
140 
141 	if (!of_property_read_u32(np, "idle-state", &mux->data.idle))
142 		mux->data.idle_in_use = true;
143 
144 	/* map address from "reg" if exists */
145 	if (of_address_to_resource(np, 0, &res) == 0) {
146 		mux->data.reg_size = resource_size(&res);
147 		mux->data.reg = devm_ioremap_resource(&pdev->dev, &res);
148 		if (IS_ERR(mux->data.reg))
149 			return PTR_ERR(mux->data.reg);
150 	}
151 
152 	return 0;
153 }
154 #else
155 static int i2c_mux_reg_probe_dt(struct regmux *mux,
156 				struct platform_device *pdev)
157 {
158 	return 0;
159 }
160 #endif
161 
162 static int i2c_mux_reg_probe(struct platform_device *pdev)
163 {
164 	struct i2c_mux_core *muxc;
165 	struct regmux *mux;
166 	struct i2c_adapter *parent;
167 	struct resource *res;
168 	unsigned int class;
169 	int i, ret, nr;
170 
171 	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
172 	if (!mux)
173 		return -ENOMEM;
174 
175 	if (dev_get_platdata(&pdev->dev)) {
176 		memcpy(&mux->data, dev_get_platdata(&pdev->dev),
177 			sizeof(mux->data));
178 	} else {
179 		ret = i2c_mux_reg_probe_dt(mux, pdev);
180 		if (ret < 0) {
181 			dev_err(&pdev->dev, "Error parsing device tree");
182 			return ret;
183 		}
184 	}
185 
186 	parent = i2c_get_adapter(mux->data.parent);
187 	if (!parent)
188 		return -EPROBE_DEFER;
189 
190 	if (!mux->data.reg) {
191 		dev_info(&pdev->dev,
192 			"Register not set, using platform resource\n");
193 		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
194 		mux->data.reg_size = resource_size(res);
195 		mux->data.reg = devm_ioremap_resource(&pdev->dev, res);
196 		if (IS_ERR(mux->data.reg)) {
197 			ret = PTR_ERR(mux->data.reg);
198 			goto err_put_parent;
199 		}
200 	}
201 
202 	if (mux->data.reg_size != 4 && mux->data.reg_size != 2 &&
203 	    mux->data.reg_size != 1) {
204 		dev_err(&pdev->dev, "Invalid register size\n");
205 		ret = -EINVAL;
206 		goto err_put_parent;
207 	}
208 
209 	muxc = i2c_mux_alloc(parent, &pdev->dev, mux->data.n_values, 0, 0,
210 			     i2c_mux_reg_select, NULL);
211 	if (!muxc) {
212 		ret = -ENOMEM;
213 		goto err_put_parent;
214 	}
215 	muxc->priv = mux;
216 
217 	platform_set_drvdata(pdev, muxc);
218 
219 	if (mux->data.idle_in_use)
220 		muxc->deselect = i2c_mux_reg_deselect;
221 
222 	for (i = 0; i < mux->data.n_values; i++) {
223 		nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;
224 		class = mux->data.classes ? mux->data.classes[i] : 0;
225 
226 		ret = i2c_mux_add_adapter(muxc, nr, mux->data.values[i], class);
227 		if (ret)
228 			goto err_del_mux_adapters;
229 	}
230 
231 	dev_dbg(&pdev->dev, "%d port mux on %s adapter\n",
232 		 mux->data.n_values, muxc->parent->name);
233 
234 	return 0;
235 
236 err_del_mux_adapters:
237 	i2c_mux_del_adapters(muxc);
238 err_put_parent:
239 	i2c_put_adapter(parent);
240 
241 	return ret;
242 }
243 
244 static int i2c_mux_reg_remove(struct platform_device *pdev)
245 {
246 	struct i2c_mux_core *muxc = platform_get_drvdata(pdev);
247 
248 	i2c_mux_del_adapters(muxc);
249 	i2c_put_adapter(muxc->parent);
250 
251 	return 0;
252 }
253 
254 static const struct of_device_id i2c_mux_reg_of_match[] = {
255 	{ .compatible = "i2c-mux-reg", },
256 	{},
257 };
258 MODULE_DEVICE_TABLE(of, i2c_mux_reg_of_match);
259 
260 static struct platform_driver i2c_mux_reg_driver = {
261 	.probe	= i2c_mux_reg_probe,
262 	.remove	= i2c_mux_reg_remove,
263 	.driver	= {
264 		.name	= "i2c-mux-reg",
265 		.of_match_table = of_match_ptr(i2c_mux_reg_of_match),
266 	},
267 };
268 
269 module_platform_driver(i2c_mux_reg_driver);
270 
271 MODULE_DESCRIPTION("Register-based I2C multiplexer driver");
272 MODULE_AUTHOR("York Sun <yorksun@freescale.com>");
273 MODULE_LICENSE("GPL");
274 MODULE_ALIAS("platform:i2c-mux-reg");
275