1 /*
2  * drivers/i2c/muxes/i2c-mux-mlxcpld.c
3  * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
4  * Copyright (c) 2016 Michael Shych <michaels@mellanox.com>
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions are met:
8  *
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. Neither the names of the copyright holders nor the names of its
15  *    contributors may be used to endorse or promote products derived from
16  *    this software without specific prior written permission.
17  *
18  * Alternatively, this software may be distributed under the terms of the
19  * GNU General Public License ("GPL") version 2 as published by the Free
20  * Software Foundation.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
23  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
26  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
27  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
28  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
29  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
30  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
31  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
32  * POSSIBILITY OF SUCH DAMAGE.
33  */
34 
35 #include <linux/device.h>
36 #include <linux/i2c.h>
37 #include <linux/i2c-mux.h>
38 #include <linux/io.h>
39 #include <linux/init.h>
40 #include <linux/module.h>
41 #include <linux/platform_data/x86/mlxcpld.h>
42 #include <linux/platform_device.h>
43 #include <linux/slab.h>
44 
45 #define CPLD_MUX_MAX_NCHANS	8
46 
47 /* mlxcpld_mux - mux control structure:
48  * @last_chan - last register value
49  * @client - I2C device client
50  */
51 struct mlxcpld_mux {
52 	u8 last_chan;
53 	struct i2c_client *client;
54 };
55 
56 /* MUX logic description.
57  * Driver can support different mux control logic, according to CPLD
58  * implementation.
59  *
60  * Connectivity schema.
61  *
62  * i2c-mlxcpld                                 Digital               Analog
63  * driver
64  * *--------*                                 * -> mux1 (virt bus2) -> mux -> |
65  * | I2CLPC | i2c physical                    * -> mux2 (virt bus3) -> mux -> |
66  * | bridge | bus 1                 *---------*                               |
67  * | logic  |---------------------> * mux reg *                               |
68  * | in CPLD|                       *---------*                               |
69  * *--------*   i2c-mux-mlxpcld          ^    * -> muxn (virt busn) -> mux -> |
70  *     |        driver                   |                                    |
71  *     |        *---------------*        |                              Devices
72  *     |        * CPLD (i2c bus)* select |
73  *     |        * registers for *--------*
74  *     |        * mux selection * deselect
75  *     |        *---------------*
76  *     |                 |
77  * <-------->     <----------->
78  * i2c cntrl      Board cntrl reg
79  * reg space      space (mux select,
80  *                IO, LED, WD, info)
81  *
82  */
83 
84 static const struct i2c_device_id mlxcpld_mux_id[] = {
85 	{ "mlxcpld_mux_module", 0 },
86 	{ }
87 };
88 MODULE_DEVICE_TABLE(i2c, mlxcpld_mux_id);
89 
90 /* Write to mux register. Don't use i2c_transfer() and i2c_smbus_xfer()
91  * for this as they will try to lock adapter a second time.
92  */
93 static int mlxcpld_mux_reg_write(struct i2c_adapter *adap,
94 				 struct i2c_client *client, u8 val)
95 {
96 	struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client->dev);
97 	union i2c_smbus_data data = { .byte = val };
98 
99 	return __i2c_smbus_xfer(adap, client->addr, client->flags,
100 				I2C_SMBUS_WRITE, pdata->sel_reg_addr,
101 				I2C_SMBUS_BYTE_DATA, &data);
102 }
103 
104 static int mlxcpld_mux_select_chan(struct i2c_mux_core *muxc, u32 chan)
105 {
106 	struct mlxcpld_mux *data = i2c_mux_priv(muxc);
107 	struct i2c_client *client = data->client;
108 	u8 regval = chan + 1;
109 	int err = 0;
110 
111 	/* Only select the channel if its different from the last channel */
112 	if (data->last_chan != regval) {
113 		err = mlxcpld_mux_reg_write(muxc->parent, client, regval);
114 		data->last_chan = err < 0 ? 0 : regval;
115 	}
116 
117 	return err;
118 }
119 
120 static int mlxcpld_mux_deselect(struct i2c_mux_core *muxc, u32 chan)
121 {
122 	struct mlxcpld_mux *data = i2c_mux_priv(muxc);
123 	struct i2c_client *client = data->client;
124 
125 	/* Deselect active channel */
126 	data->last_chan = 0;
127 
128 	return mlxcpld_mux_reg_write(muxc->parent, client, data->last_chan);
129 }
130 
131 /* Probe/reomove functions */
132 static int mlxcpld_mux_probe(struct i2c_client *client,
133 			     const struct i2c_device_id *id)
134 {
135 	struct i2c_adapter *adap = client->adapter;
136 	struct mlxcpld_mux_plat_data *pdata = dev_get_platdata(&client->dev);
137 	struct i2c_mux_core *muxc;
138 	int num, force;
139 	struct mlxcpld_mux *data;
140 	int err;
141 
142 	if (!pdata)
143 		return -EINVAL;
144 
145 	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
146 		return -ENODEV;
147 
148 	muxc = i2c_mux_alloc(adap, &client->dev, CPLD_MUX_MAX_NCHANS,
149 			     sizeof(*data), 0, mlxcpld_mux_select_chan,
150 			     mlxcpld_mux_deselect);
151 	if (!muxc)
152 		return -ENOMEM;
153 
154 	data = i2c_mux_priv(muxc);
155 	i2c_set_clientdata(client, muxc);
156 	data->client = client;
157 	data->last_chan = 0; /* force the first selection */
158 
159 	/* Create an adapter for each channel. */
160 	for (num = 0; num < CPLD_MUX_MAX_NCHANS; num++) {
161 		if (num >= pdata->num_adaps)
162 			/* discard unconfigured channels */
163 			break;
164 
165 		force = pdata->adap_ids[num];
166 
167 		err = i2c_mux_add_adapter(muxc, force, num, 0);
168 		if (err)
169 			goto virt_reg_failed;
170 	}
171 
172 	return 0;
173 
174 virt_reg_failed:
175 	i2c_mux_del_adapters(muxc);
176 	return err;
177 }
178 
179 static int mlxcpld_mux_remove(struct i2c_client *client)
180 {
181 	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
182 
183 	i2c_mux_del_adapters(muxc);
184 	return 0;
185 }
186 
187 static struct i2c_driver mlxcpld_mux_driver = {
188 	.driver		= {
189 		.name	= "mlxcpld-mux",
190 	},
191 	.probe		= mlxcpld_mux_probe,
192 	.remove		= mlxcpld_mux_remove,
193 	.id_table	= mlxcpld_mux_id,
194 };
195 
196 module_i2c_driver(mlxcpld_mux_driver);
197 
198 MODULE_AUTHOR("Michael Shych (michaels@mellanox.com)");
199 MODULE_DESCRIPTION("Mellanox I2C-CPLD-MUX driver");
200 MODULE_LICENSE("Dual BSD/GPL");
201 MODULE_ALIAS("platform:i2c-mux-mlxcpld");
202