1/*
  2 * I2C multiplexer using GPIO API
  3 *
  4 * Peter Korsgaard <peter.korsgaard@barco.com>
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License version 2 as
  8 * published by the Free Software Foundation.
  9 */
 10
 11#include <linux/i2c.h>
 12#include <linux/i2c-mux.h>
 13#include <linux/i2c-mux-gpio.h>
 14#include <linux/platform_device.h>
 15#include <linux/module.h>
 16#include <linux/slab.h>
 17#include <linux/gpio.h>
 18#include <linux/of_gpio.h>
 19
 20struct gpiomux {
 21	struct i2c_adapter *parent;
 22	struct i2c_adapter **adap; /* child busses */
 23	struct i2c_mux_gpio_platform_data data;
 24	unsigned gpio_base;
 25};
 26
 27static void i2c_mux_gpio_set(const struct gpiomux *mux, unsigned val)
 28{
 29	int i;
 30
 31	for (i = 0; i < mux->data.n_gpios; i++)
 32		gpio_set_value_cansleep(mux->gpio_base + mux->data.gpios[i],
 33					val & (1 << i));
 34}
 35
 36static int i2c_mux_gpio_select(struct i2c_adapter *adap, void *data, u32 chan)
 37{
 38	struct gpiomux *mux = data;
 39
 40	i2c_mux_gpio_set(mux, chan);
 41
 42	return 0;
 43}
 44
 45static int i2c_mux_gpio_deselect(struct i2c_adapter *adap, void *data, u32 chan)
 46{
 47	struct gpiomux *mux = data;
 48
 49	i2c_mux_gpio_set(mux, mux->data.idle);
 50
 51	return 0;
 52}
 53
 54static int match_gpio_chip_by_label(struct gpio_chip *chip,
 55					      void *data)
 56{
 57	return !strcmp(chip->label, data);
 58}
 59
 60#ifdef CONFIG_OF
 61static int i2c_mux_gpio_probe_dt(struct gpiomux *mux,
 62					struct platform_device *pdev)
 63{
 64	struct device_node *np = pdev->dev.of_node;
 65	struct device_node *adapter_np, *child;
 66	struct i2c_adapter *adapter;
 67	unsigned *values, *gpios;
 68	int i = 0, ret;
 69
 70	if (!np)
 71		return -ENODEV;
 72
 73	adapter_np = of_parse_phandle(np, "i2c-parent", 0);
 74	if (!adapter_np) {
 75		dev_err(&pdev->dev, "Cannot parse i2c-parent\n");
 76		return -ENODEV;
 77	}
 78	adapter = of_find_i2c_adapter_by_node(adapter_np);
 79	if (!adapter) {
 80		dev_err(&pdev->dev, "Cannot find parent bus\n");
 81		return -EPROBE_DEFER;
 82	}
 83	mux->data.parent = i2c_adapter_id(adapter);
 84	put_device(&adapter->dev);
 85
 86	mux->data.n_values = of_get_child_count(np);
 87
 88	values = devm_kzalloc(&pdev->dev,
 89			      sizeof(*mux->data.values) * mux->data.n_values,
 90			      GFP_KERNEL);
 91	if (!values) {
 92		dev_err(&pdev->dev, "Cannot allocate values array");
 93		return -ENOMEM;
 94	}
 95
 96	for_each_child_of_node(np, child) {
 97		of_property_read_u32(child, "reg", values + i);
 98		i++;
 99	}
100	mux->data.values = values;
101
102	if (of_property_read_u32(np, "idle-state", &mux->data.idle))
103		mux->data.idle = I2C_MUX_GPIO_NO_IDLE;
104
105	mux->data.n_gpios = of_gpio_named_count(np, "mux-gpios");
106	if (mux->data.n_gpios < 0) {
107		dev_err(&pdev->dev, "Missing mux-gpios property in the DT.\n");
108		return -EINVAL;
109	}
110
111	gpios = devm_kzalloc(&pdev->dev,
112			     sizeof(*mux->data.gpios) * mux->data.n_gpios, GFP_KERNEL);
113	if (!gpios) {
114		dev_err(&pdev->dev, "Cannot allocate gpios array");
115		return -ENOMEM;
116	}
117
118	for (i = 0; i < mux->data.n_gpios; i++) {
119		ret = of_get_named_gpio(np, "mux-gpios", i);
120		if (ret < 0)
121			return ret;
122		gpios[i] = ret;
123	}
124
125	mux->data.gpios = gpios;
126
127	return 0;
128}
129#else
130static int i2c_mux_gpio_probe_dt(struct gpiomux *mux,
131					struct platform_device *pdev)
132{
133	return 0;
134}
135#endif
136
137static int i2c_mux_gpio_probe(struct platform_device *pdev)
138{
139	struct gpiomux *mux;
140	struct i2c_adapter *parent;
141	int (*deselect) (struct i2c_adapter *, void *, u32);
142	unsigned initial_state, gpio_base;
143	int i, ret;
144
145	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
146	if (!mux) {
147		dev_err(&pdev->dev, "Cannot allocate gpiomux structure");
148		return -ENOMEM;
149	}
150
151	platform_set_drvdata(pdev, mux);
152
153	if (!dev_get_platdata(&pdev->dev)) {
154		ret = i2c_mux_gpio_probe_dt(mux, pdev);
155		if (ret < 0)
156			return ret;
157	} else {
158		memcpy(&mux->data, dev_get_platdata(&pdev->dev),
159			sizeof(mux->data));
160	}
161
162	/*
163	 * If a GPIO chip name is provided, the GPIO pin numbers provided are
164	 * relative to its base GPIO number. Otherwise they are absolute.
165	 */
166	if (mux->data.gpio_chip) {
167		struct gpio_chip *gpio;
168
169		gpio = gpiochip_find(mux->data.gpio_chip,
170				     match_gpio_chip_by_label);
171		if (!gpio)
172			return -EPROBE_DEFER;
173
174		gpio_base = gpio->base;
175	} else {
176		gpio_base = 0;
177	}
178
179	parent = i2c_get_adapter(mux->data.parent);
180	if (!parent) {
181		dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
182			mux->data.parent);
183		return -EPROBE_DEFER;
184	}
185
186	mux->parent = parent;
187	mux->gpio_base = gpio_base;
188
189	mux->adap = devm_kzalloc(&pdev->dev,
190				 sizeof(*mux->adap) * mux->data.n_values,
191				 GFP_KERNEL);
192	if (!mux->adap) {
193		dev_err(&pdev->dev, "Cannot allocate i2c_adapter structure");
194		ret = -ENOMEM;
195		goto alloc_failed;
196	}
197
198	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE) {
199		initial_state = mux->data.idle;
200		deselect = i2c_mux_gpio_deselect;
201	} else {
202		initial_state = mux->data.values[0];
203		deselect = NULL;
204	}
205
206	for (i = 0; i < mux->data.n_gpios; i++) {
207		ret = gpio_request(gpio_base + mux->data.gpios[i], "i2c-mux-gpio");
208		if (ret) {
209			dev_err(&pdev->dev, "Failed to request GPIO %d\n",
210				mux->data.gpios[i]);
211			goto err_request_gpio;
212		}
213
214		ret = gpio_direction_output(gpio_base + mux->data.gpios[i],
215					    initial_state & (1 << i));
216		if (ret) {
217			dev_err(&pdev->dev,
218				"Failed to set direction of GPIO %d to output\n",
219				mux->data.gpios[i]);
220			i++;	/* gpio_request above succeeded, so must free */
221			goto err_request_gpio;
222		}
223	}
224
225	for (i = 0; i < mux->data.n_values; i++) {
226		u32 nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;
227		unsigned int class = mux->data.classes ? mux->data.classes[i] : 0;
228
229		mux->adap[i] = i2c_add_mux_adapter(parent, &pdev->dev, mux, nr,
230						   mux->data.values[i], class,
231						   i2c_mux_gpio_select, deselect);
232		if (!mux->adap[i]) {
233			ret = -ENODEV;
234			dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
235			goto add_adapter_failed;
236		}
237	}
238
239	dev_info(&pdev->dev, "%d port mux on %s adapter\n",
240		 mux->data.n_values, parent->name);
241
242	return 0;
243
244add_adapter_failed:
245	for (; i > 0; i--)
246		i2c_del_mux_adapter(mux->adap[i - 1]);
247	i = mux->data.n_gpios;
248err_request_gpio:
249	for (; i > 0; i--)
250		gpio_free(gpio_base + mux->data.gpios[i - 1]);
251alloc_failed:
252	i2c_put_adapter(parent);
253
254	return ret;
255}
256
257static int i2c_mux_gpio_remove(struct platform_device *pdev)
258{
259	struct gpiomux *mux = platform_get_drvdata(pdev);
260	int i;
261
262	for (i = 0; i < mux->data.n_values; i++)
263		i2c_del_mux_adapter(mux->adap[i]);
264
265	for (i = 0; i < mux->data.n_gpios; i++)
266		gpio_free(mux->gpio_base + mux->data.gpios[i]);
267
268	i2c_put_adapter(mux->parent);
269
270	return 0;
271}
272
273static const struct of_device_id i2c_mux_gpio_of_match[] = {
274	{ .compatible = "i2c-mux-gpio", },
275	{},
276};
277MODULE_DEVICE_TABLE(of, i2c_mux_gpio_of_match);
278
279static struct platform_driver i2c_mux_gpio_driver = {
280	.probe	= i2c_mux_gpio_probe,
281	.remove	= i2c_mux_gpio_remove,
282	.driver	= {
283		.owner	= THIS_MODULE,
284		.name	= "i2c-mux-gpio",
285		.of_match_table = i2c_mux_gpio_of_match,
286	},
287};
288
289module_platform_driver(i2c_mux_gpio_driver);
290
291MODULE_DESCRIPTION("GPIO-based I2C multiplexer driver");
292MODULE_AUTHOR("Peter Korsgaard <peter.korsgaard@barco.com>");
293MODULE_LICENSE("GPL");
294MODULE_ALIAS("platform:i2c-mux-gpio");