1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * i2c-nforce2-s4985.c - i2c-nforce2 extras for the Tyan S4985 motherboard
4  *
5  * Copyright (C) 2008 Jean Delvare <jdelvare@suse.de>
6  */
7 
8 /*
9  * We select the channels by sending commands to the Philips
10  * PCA9556 chip at I2C address 0x18. The main adapter is used for
11  * the non-multiplexed part of the bus, and 4 virtual adapters
12  * are defined for the multiplexed addresses: 0x50-0x53 (memory
13  * module EEPROM) located on channels 1-4. We define one virtual
14  * adapter per CPU, which corresponds to one multiplexed channel:
15  *   CPU0: virtual adapter 1, channel 1
16  *   CPU1: virtual adapter 2, channel 2
17  *   CPU2: virtual adapter 3, channel 3
18  *   CPU3: virtual adapter 4, channel 4
19  */
20 
21 #include <linux/module.h>
22 #include <linux/kernel.h>
23 #include <linux/slab.h>
24 #include <linux/init.h>
25 #include <linux/i2c.h>
26 #include <linux/mutex.h>
27 
28 extern struct i2c_adapter *nforce2_smbus;
29 
30 static struct i2c_adapter *s4985_adapter;
31 static struct i2c_algorithm *s4985_algo;
32 
33 /* Wrapper access functions for multiplexed SMBus */
34 static DEFINE_MUTEX(nforce2_lock);
35 
nforce2_access_virt0(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)36 static s32 nforce2_access_virt0(struct i2c_adapter *adap, u16 addr,
37 				unsigned short flags, char read_write,
38 				u8 command, int size,
39 				union i2c_smbus_data *data)
40 {
41 	int error;
42 
43 	/* We exclude the multiplexed addresses */
44 	if ((addr & 0xfc) == 0x50 || (addr & 0xfc) == 0x30
45 	 || addr == 0x18)
46 		return -ENXIO;
47 
48 	mutex_lock(&nforce2_lock);
49 	error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
50 						command, size, data);
51 	mutex_unlock(&nforce2_lock);
52 
53 	return error;
54 }
55 
56 /* We remember the last used channels combination so as to only switch
57    channels when it is really needed. This greatly reduces the SMBus
58    overhead, but also assumes that nobody will be writing to the PCA9556
59    in our back. */
60 static u8 last_channels;
61 
nforce2_access_channel(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data,u8 channels)62 static inline s32 nforce2_access_channel(struct i2c_adapter *adap, u16 addr,
63 					 unsigned short flags, char read_write,
64 					 u8 command, int size,
65 					 union i2c_smbus_data *data,
66 					 u8 channels)
67 {
68 	int error;
69 
70 	/* We exclude the non-multiplexed addresses */
71 	if ((addr & 0xfc) != 0x50 && (addr & 0xfc) != 0x30)
72 		return -ENXIO;
73 
74 	mutex_lock(&nforce2_lock);
75 	if (last_channels != channels) {
76 		union i2c_smbus_data mplxdata;
77 		mplxdata.byte = channels;
78 
79 		error = nforce2_smbus->algo->smbus_xfer(adap, 0x18, 0,
80 							I2C_SMBUS_WRITE, 0x01,
81 							I2C_SMBUS_BYTE_DATA,
82 							&mplxdata);
83 		if (error)
84 			goto UNLOCK;
85 		last_channels = channels;
86 	}
87 	error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
88 						command, size, data);
89 
90 UNLOCK:
91 	mutex_unlock(&nforce2_lock);
92 	return error;
93 }
94 
nforce2_access_virt1(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)95 static s32 nforce2_access_virt1(struct i2c_adapter *adap, u16 addr,
96 				unsigned short flags, char read_write,
97 				u8 command, int size,
98 				union i2c_smbus_data *data)
99 {
100 	/* CPU0: channel 1 enabled */
101 	return nforce2_access_channel(adap, addr, flags, read_write, command,
102 				      size, data, 0x02);
103 }
104 
nforce2_access_virt2(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)105 static s32 nforce2_access_virt2(struct i2c_adapter *adap, u16 addr,
106 				unsigned short flags, char read_write,
107 				u8 command, int size,
108 				union i2c_smbus_data *data)
109 {
110 	/* CPU1: channel 2 enabled */
111 	return nforce2_access_channel(adap, addr, flags, read_write, command,
112 				      size, data, 0x04);
113 }
114 
nforce2_access_virt3(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)115 static s32 nforce2_access_virt3(struct i2c_adapter *adap, u16 addr,
116 				unsigned short flags, char read_write,
117 				u8 command, int size,
118 				union i2c_smbus_data *data)
119 {
120 	/* CPU2: channel 3 enabled */
121 	return nforce2_access_channel(adap, addr, flags, read_write, command,
122 				      size, data, 0x08);
123 }
124 
nforce2_access_virt4(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)125 static s32 nforce2_access_virt4(struct i2c_adapter *adap, u16 addr,
126 				unsigned short flags, char read_write,
127 				u8 command, int size,
128 				union i2c_smbus_data *data)
129 {
130 	/* CPU3: channel 4 enabled */
131 	return nforce2_access_channel(adap, addr, flags, read_write, command,
132 				      size, data, 0x10);
133 }
134 
nforce2_s4985_init(void)135 static int __init nforce2_s4985_init(void)
136 {
137 	int i, error;
138 	union i2c_smbus_data ioconfig;
139 
140 	if (!nforce2_smbus)
141 		return -ENODEV;
142 
143 	/* Configure the PCA9556 multiplexer */
144 	ioconfig.byte = 0x00; /* All I/O to output mode */
145 	error = i2c_smbus_xfer(nforce2_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
146 			       I2C_SMBUS_BYTE_DATA, &ioconfig);
147 	if (error) {
148 		dev_err(&nforce2_smbus->dev, "PCA9556 configuration failed\n");
149 		error = -EIO;
150 		goto ERROR0;
151 	}
152 
153 	/* Unregister physical bus */
154 	i2c_del_adapter(nforce2_smbus);
155 
156 	printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4985\n");
157 	/* Define the 5 virtual adapters and algorithms structures */
158 	s4985_adapter = kcalloc(5, sizeof(struct i2c_adapter), GFP_KERNEL);
159 	if (!s4985_adapter) {
160 		error = -ENOMEM;
161 		goto ERROR1;
162 	}
163 	s4985_algo = kcalloc(5, sizeof(struct i2c_algorithm), GFP_KERNEL);
164 	if (!s4985_algo) {
165 		error = -ENOMEM;
166 		goto ERROR2;
167 	}
168 
169 	/* Fill in the new structures */
170 	s4985_algo[0] = *(nforce2_smbus->algo);
171 	s4985_algo[0].smbus_xfer = nforce2_access_virt0;
172 	s4985_adapter[0] = *nforce2_smbus;
173 	s4985_adapter[0].algo = s4985_algo;
174 	s4985_adapter[0].dev.parent = nforce2_smbus->dev.parent;
175 	for (i = 1; i < 5; i++) {
176 		s4985_algo[i] = *(nforce2_smbus->algo);
177 		s4985_adapter[i] = *nforce2_smbus;
178 		snprintf(s4985_adapter[i].name, sizeof(s4985_adapter[i].name),
179 			 "SMBus nForce2 adapter (CPU%d)", i - 1);
180 		s4985_adapter[i].algo = s4985_algo + i;
181 		s4985_adapter[i].dev.parent = nforce2_smbus->dev.parent;
182 	}
183 	s4985_algo[1].smbus_xfer = nforce2_access_virt1;
184 	s4985_algo[2].smbus_xfer = nforce2_access_virt2;
185 	s4985_algo[3].smbus_xfer = nforce2_access_virt3;
186 	s4985_algo[4].smbus_xfer = nforce2_access_virt4;
187 
188 	/* Register virtual adapters */
189 	for (i = 0; i < 5; i++) {
190 		error = i2c_add_adapter(s4985_adapter + i);
191 		if (error) {
192 			printk(KERN_ERR "i2c-nforce2-s4985: "
193 			       "Virtual adapter %d registration "
194 			       "failed, module not inserted\n", i);
195 			for (i--; i >= 0; i--)
196 				i2c_del_adapter(s4985_adapter + i);
197 			goto ERROR3;
198 		}
199 	}
200 
201 	return 0;
202 
203 ERROR3:
204 	kfree(s4985_algo);
205 	s4985_algo = NULL;
206 ERROR2:
207 	kfree(s4985_adapter);
208 	s4985_adapter = NULL;
209 ERROR1:
210 	/* Restore physical bus */
211 	i2c_add_adapter(nforce2_smbus);
212 ERROR0:
213 	return error;
214 }
215 
nforce2_s4985_exit(void)216 static void __exit nforce2_s4985_exit(void)
217 {
218 	if (s4985_adapter) {
219 		int i;
220 
221 		for (i = 0; i < 5; i++)
222 			i2c_del_adapter(s4985_adapter+i);
223 		kfree(s4985_adapter);
224 		s4985_adapter = NULL;
225 	}
226 	kfree(s4985_algo);
227 	s4985_algo = NULL;
228 
229 	/* Restore physical bus */
230 	if (i2c_add_adapter(nforce2_smbus))
231 		printk(KERN_ERR "i2c-nforce2-s4985: "
232 		       "Physical bus restoration failed\n");
233 }
234 
235 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
236 MODULE_DESCRIPTION("S4985 SMBus multiplexing");
237 MODULE_LICENSE("GPL");
238 
239 module_init(nforce2_s4985_init);
240 module_exit(nforce2_s4985_exit);
241