drivers/i2c/busses/i2c-nforce2-s4985.c

   1 /*
   2  * i2c-nforce2-s4985.c - i2c-nforce2 extras for the Tyan S4985 motherboard
   3  *
   4  * Copyright (C) 2008 Jean Delvare <jdelvare@suse.de>
   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 as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  */
  16
  17 /*
  18  * We select the channels by sending commands to the Philips
  19  * PCA9556 chip at I2C address 0x18. The main adapter is used for
  20  * the non-multiplexed part of the bus, and 4 virtual adapters
  21  * are defined for the multiplexed addresses: 0x50-0x53 (memory
  22  * module EEPROM) located on channels 1-4. We define one virtual
  23  * adapter per CPU, which corresponds to one multiplexed channel:
  24  *   CPU0: virtual adapter 1, channel 1
  25  *   CPU1: virtual adapter 2, channel 2
  26  *   CPU2: virtual adapter 3, channel 3
  27  *   CPU3: virtual adapter 4, channel 4
  28  */
  29
  30 #include <linux/module.h>
  31 #include <linux/kernel.h>
  32 #include <linux/slab.h>
  33 #include <linux/init.h>
  34 #include <linux/i2c.h>
  35 #include <linux/mutex.h>
  36
  37 extern struct i2c_adapter *nforce2_smbus;
  38
  39 static struct i2c_adapter *s4985_adapter;
  40 static struct i2c_algorithm *s4985_algo;
  41
  42 /* Wrapper access functions for multiplexed SMBus */
  43 static DEFINE_MUTEX(nforce2_lock);
  44
  45 static s32 nforce2_access_virt0(struct i2c_adapter *adap, u16 addr,
  46                                 unsigned short flags, char read_write,
  47                                 u8 command, int size,
  48                                 union i2c_smbus_data *data)
  49 {
  50         int error;
  51
  52         /* We exclude the multiplexed addresses */
  53         if ((addr & 0xfc) == 0x50 || (addr & 0xfc) == 0x30
  54          || addr == 0x18)
  55                 return -ENXIO;
  56
  57         mutex_lock(&nforce2_lock);
  58         error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
  59                                                 command, size, data);
  60         mutex_unlock(&nforce2_lock);
  61
  62         return error;
  63 }
  64
  65 /* We remember the last used channels combination so as to only switch
  66    channels when it is really needed. This greatly reduces the SMBus
  67    overhead, but also assumes that nobody will be writing to the PCA9556
  68    in our back. */
  69 static u8 last_channels;
  70
  71 static inline s32 nforce2_access_channel(struct i2c_adapter *adap, u16 addr,
  72                                          unsigned short flags, char read_write,
  73                                          u8 command, int size,
  74                                          union i2c_smbus_data *data,
  75                                          u8 channels)
  76 {
  77         int error;
  78
  79         /* We exclude the non-multiplexed addresses */
  80         if ((addr & 0xfc) != 0x50 && (addr & 0xfc) != 0x30)
  81                 return -ENXIO;
  82
  83         mutex_lock(&nforce2_lock);
  84         if (last_channels != channels) {
  85                 union i2c_smbus_data mplxdata;
  86                 mplxdata.byte = channels;
  87
  88                 error = nforce2_smbus->algo->smbus_xfer(adap, 0x18, 0,
  89                                                         I2C_SMBUS_WRITE, 0x01,
  90                                                         I2C_SMBUS_BYTE_DATA,
  91                                                         &mplxdata);
  92                 if (error)
  93                         goto UNLOCK;
  94                 last_channels = channels;
  95         }
  96         error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
  97                                                 command, size, data);
  98
  99 UNLOCK:
 100         mutex_unlock(&nforce2_lock);
 101         return error;
 102 }
 103
 104 static s32 nforce2_access_virt1(struct i2c_adapter *adap, u16 addr,
 105                                 unsigned short flags, char read_write,
 106                                 u8 command, int size,
 107                                 union i2c_smbus_data *data)
 108 {
 109         /* CPU0: channel 1 enabled */
 110         return nforce2_access_channel(adap, addr, flags, read_write, command,
 111                                       size, data, 0x02);
 112 }
 113
 114 static s32 nforce2_access_virt2(struct i2c_adapter *adap, u16 addr,
 115                                 unsigned short flags, char read_write,
 116                                 u8 command, int size,
 117                                 union i2c_smbus_data *data)
 118 {
 119         /* CPU1: channel 2 enabled */
 120         return nforce2_access_channel(adap, addr, flags, read_write, command,
 121                                       size, data, 0x04);
 122 }
 123
 124 static s32 nforce2_access_virt3(struct i2c_adapter *adap, u16 addr,
 125                                 unsigned short flags, char read_write,
 126                                 u8 command, int size,
 127                                 union i2c_smbus_data *data)
 128 {
 129         /* CPU2: channel 3 enabled */
 130         return nforce2_access_channel(adap, addr, flags, read_write, command,
 131                                       size, data, 0x08);
 132 }
 133
 134 static s32 nforce2_access_virt4(struct i2c_adapter *adap, u16 addr,
 135                                 unsigned short flags, char read_write,
 136                                 u8 command, int size,
 137                                 union i2c_smbus_data *data)
 138 {
 139         /* CPU3: channel 4 enabled */
 140         return nforce2_access_channel(adap, addr, flags, read_write, command,
 141                                       size, data, 0x10);
 142 }
 143
 144 static int __init nforce2_s4985_init(void)
 145 {
 146         int i, error;
 147         union i2c_smbus_data ioconfig;
 148
 149         if (!nforce2_smbus)
 150                 return -ENODEV;
 151
 152         /* Configure the PCA9556 multiplexer */
 153         ioconfig.byte = 0x00; /* All I/O to output mode */
 154         error = i2c_smbus_xfer(nforce2_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
 155                                I2C_SMBUS_BYTE_DATA, &ioconfig);
 156         if (error) {
 157                 dev_err(&nforce2_smbus->dev, "PCA9556 configuration failed\n");
 158                 error = -EIO;
 159                 goto ERROR0;
 160         }
 161
 162         /* Unregister physical bus */
 163         i2c_del_adapter(nforce2_smbus);
 164
 165         printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4985\n");
 166         /* Define the 5 virtual adapters and algorithms structures */
 167         s4985_adapter = kzalloc(5 * sizeof(struct i2c_adapter), GFP_KERNEL);
 168         if (!s4985_adapter) {
 169                 error = -ENOMEM;
 170                 goto ERROR1;
 171         }
 172         s4985_algo = kzalloc(5 * sizeof(struct i2c_algorithm), GFP_KERNEL);
 173         if (!s4985_algo) {
 174                 error = -ENOMEM;
 175                 goto ERROR2;
 176         }
 177
 178         /* Fill in the new structures */
 179         s4985_algo[0] = *(nforce2_smbus->algo);
 180         s4985_algo[0].smbus_xfer = nforce2_access_virt0;
 181         s4985_adapter[0] = *nforce2_smbus;
 182         s4985_adapter[0].algo = s4985_algo;
 183         s4985_adapter[0].dev.parent = nforce2_smbus->dev.parent;
 184         for (i = 1; i < 5; i++) {
 185                 s4985_algo[i] = *(nforce2_smbus->algo);
 186                 s4985_adapter[i] = *nforce2_smbus;
 187                 snprintf(s4985_adapter[i].name, sizeof(s4985_adapter[i].name),
 188                          "SMBus nForce2 adapter (CPU%d)", i - 1);
 189                 s4985_adapter[i].algo = s4985_algo + i;
 190                 s4985_adapter[i].dev.parent = nforce2_smbus->dev.parent;
 191         }
 192         s4985_algo[1].smbus_xfer = nforce2_access_virt1;
 193         s4985_algo[2].smbus_xfer = nforce2_access_virt2;
 194         s4985_algo[3].smbus_xfer = nforce2_access_virt3;
 195         s4985_algo[4].smbus_xfer = nforce2_access_virt4;
 196
 197         /* Register virtual adapters */
 198         for (i = 0; i < 5; i++) {
 199                 error = i2c_add_adapter(s4985_adapter + i);
 200                 if (error) {
 201                         printk(KERN_ERR "i2c-nforce2-s4985: "
 202                                "Virtual adapter %d registration "
 203                                "failed, module not inserted\n", i);
 204                         for (i--; i >= 0; i--)
 205                                 i2c_del_adapter(s4985_adapter + i);
 206                         goto ERROR3;
 207                 }
 208         }
 209
 210         return 0;
 211
 212 ERROR3:
 213         kfree(s4985_algo);
 214         s4985_algo = NULL;
 215 ERROR2:
 216         kfree(s4985_adapter);
 217         s4985_adapter = NULL;
 218 ERROR1:
 219         /* Restore physical bus */
 220         i2c_add_adapter(nforce2_smbus);
 221 ERROR0:
 222         return error;
 223 }
 224
 225 static void __exit nforce2_s4985_exit(void)
 226 {
 227         if (s4985_adapter) {
 228                 int i;
 229
 230                 for (i = 0; i < 5; i++)
 231                         i2c_del_adapter(s4985_adapter+i);
 232                 kfree(s4985_adapter);
 233                 s4985_adapter = NULL;
 234         }
 235         kfree(s4985_algo);
 236         s4985_algo = NULL;
 237
 238         /* Restore physical bus */
 239         if (i2c_add_adapter(nforce2_smbus))
 240                 printk(KERN_ERR "i2c-nforce2-s4985: "
 241                        "Physical bus restoration failed\n");
 242 }
 243
 244 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
 245 MODULE_DESCRIPTION("S4985 SMBus multiplexing");
 246 MODULE_LICENSE("GPL");
 247
 248 module_init(nforce2_s4985_init);
 249 module_exit(nforce2_s4985_exit);