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  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 /*
  22  * We select the channels by sending commands to the Philips
  23  * PCA9556 chip at I2C address 0x18. The main adapter is used for
  24  * the non-multiplexed part of the bus, and 4 virtual adapters
  25  * are defined for the multiplexed addresses: 0x50-0x53 (memory
  26  * module EEPROM) located on channels 1-4. We define one virtual
  27  * adapter per CPU, which corresponds to one multiplexed channel:
  28  *   CPU0: virtual adapter 1, channel 1
  29  *   CPU1: virtual adapter 2, channel 2
  30  *   CPU2: virtual adapter 3, channel 3
  31  *   CPU3: virtual adapter 4, channel 4
  32  */
  33
  34 #include <linux/module.h>
  35 #include <linux/kernel.h>
  36 #include <linux/slab.h>
  37 #include <linux/init.h>
  38 #include <linux/i2c.h>
  39 #include <linux/mutex.h>
  40
  41 extern struct i2c_adapter *nforce2_smbus;
  42
  43 static struct i2c_adapter *s4985_adapter;
  44 static struct i2c_algorithm *s4985_algo;
  45
  46 /* Wrapper access functions for multiplexed SMBus */
  47 static DEFINE_MUTEX(nforce2_lock);
  48
  49 static s32 nforce2_access_virt0(struct i2c_adapter *adap, u16 addr,
  50                                 unsigned short flags, char read_write,
  51                                 u8 command, int size,
  52                                 union i2c_smbus_data *data)
  53 {
  54         int error;
  55
  56         /* We exclude the multiplexed addresses */
  57         if ((addr & 0xfc) == 0x50 || (addr & 0xfc) == 0x30
  58          || addr == 0x18)
  59                 return -ENXIO;
  60
  61         mutex_lock(&nforce2_lock);
  62         error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
  63                                                 command, size, data);
  64         mutex_unlock(&nforce2_lock);
  65
  66         return error;
  67 }
  68
  69 /* We remember the last used channels combination so as to only switch
  70    channels when it is really needed. This greatly reduces the SMBus
  71    overhead, but also assumes that nobody will be writing to the PCA9556
  72    in our back. */
  73 static u8 last_channels;
  74
  75 static inline s32 nforce2_access_channel(struct i2c_adapter *adap, u16 addr,
  76                                          unsigned short flags, char read_write,
  77                                          u8 command, int size,
  78                                          union i2c_smbus_data *data,
  79                                          u8 channels)
  80 {
  81         int error;
  82
  83         /* We exclude the non-multiplexed addresses */
  84         if ((addr & 0xfc) != 0x50 && (addr & 0xfc) != 0x30)
  85                 return -ENXIO;
  86
  87         mutex_lock(&nforce2_lock);
  88         if (last_channels != channels) {
  89                 union i2c_smbus_data mplxdata;
  90                 mplxdata.byte = channels;
  91
  92                 error = nforce2_smbus->algo->smbus_xfer(adap, 0x18, 0,
  93                                                         I2C_SMBUS_WRITE, 0x01,
  94                                                         I2C_SMBUS_BYTE_DATA,
  95                                                         &mplxdata);
  96                 if (error)
  97                         goto UNLOCK;
  98                 last_channels = channels;
  99         }
 100         error = nforce2_smbus->algo->smbus_xfer(adap, addr, flags, read_write,
 101                                                 command, size, data);
 102
 103 UNLOCK:
 104         mutex_unlock(&nforce2_lock);
 105         return error;
 106 }
 107
 108 static s32 nforce2_access_virt1(struct i2c_adapter *adap, u16 addr,
 109                                 unsigned short flags, char read_write,
 110                                 u8 command, int size,
 111                                 union i2c_smbus_data *data)
 112 {
 113         /* CPU0: channel 1 enabled */
 114         return nforce2_access_channel(adap, addr, flags, read_write, command,
 115                                       size, data, 0x02);
 116 }
 117
 118 static s32 nforce2_access_virt2(struct i2c_adapter *adap, u16 addr,
 119                                 unsigned short flags, char read_write,
 120                                 u8 command, int size,
 121                                 union i2c_smbus_data *data)
 122 {
 123         /* CPU1: channel 2 enabled */
 124         return nforce2_access_channel(adap, addr, flags, read_write, command,
 125                                       size, data, 0x04);
 126 }
 127
 128 static s32 nforce2_access_virt3(struct i2c_adapter *adap, u16 addr,
 129                                 unsigned short flags, char read_write,
 130                                 u8 command, int size,
 131                                 union i2c_smbus_data *data)
 132 {
 133         /* CPU2: channel 3 enabled */
 134         return nforce2_access_channel(adap, addr, flags, read_write, command,
 135                                       size, data, 0x08);
 136 }
 137
 138 static s32 nforce2_access_virt4(struct i2c_adapter *adap, u16 addr,
 139                                 unsigned short flags, char read_write,
 140                                 u8 command, int size,
 141                                 union i2c_smbus_data *data)
 142 {
 143         /* CPU3: channel 4 enabled */
 144         return nforce2_access_channel(adap, addr, flags, read_write, command,
 145                                       size, data, 0x10);
 146 }
 147
 148 static int __init nforce2_s4985_init(void)
 149 {
 150         int i, error;
 151         union i2c_smbus_data ioconfig;
 152
 153         if (!nforce2_smbus)
 154                 return -ENODEV;
 155
 156         /* Configure the PCA9556 multiplexer */
 157         ioconfig.byte = 0x00; /* All I/O to output mode */
 158         error = i2c_smbus_xfer(nforce2_smbus, 0x18, 0, I2C_SMBUS_WRITE, 0x03,
 159                                I2C_SMBUS_BYTE_DATA, &ioconfig);
 160         if (error) {
 161                 dev_err(&nforce2_smbus->dev, "PCA9556 configuration failed\n");
 162                 error = -EIO;
 163                 goto ERROR0;
 164         }
 165
 166         /* Unregister physical bus */
 167         i2c_del_adapter(nforce2_smbus);
 168
 169         printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4985\n");
 170         /* Define the 5 virtual adapters and algorithms structures */
 171         s4985_adapter = kzalloc(5 * sizeof(struct i2c_adapter), GFP_KERNEL);
 172         if (!s4985_adapter) {
 173                 error = -ENOMEM;
 174                 goto ERROR1;
 175         }
 176         s4985_algo = kzalloc(5 * sizeof(struct i2c_algorithm), GFP_KERNEL);
 177         if (!s4985_algo) {
 178                 error = -ENOMEM;
 179                 goto ERROR2;
 180         }
 181
 182         /* Fill in the new structures */
 183         s4985_algo[0] = *(nforce2_smbus->algo);
 184         s4985_algo[0].smbus_xfer = nforce2_access_virt0;
 185         s4985_adapter[0] = *nforce2_smbus;
 186         s4985_adapter[0].algo = s4985_algo;
 187         s4985_adapter[0].dev.parent = nforce2_smbus->dev.parent;
 188         for (i = 1; i < 5; i++) {
 189                 s4985_algo[i] = *(nforce2_smbus->algo);
 190                 s4985_adapter[i] = *nforce2_smbus;
 191                 snprintf(s4985_adapter[i].name, sizeof(s4985_adapter[i].name),
 192                          "SMBus nForce2 adapter (CPU%d)", i - 1);
 193                 s4985_adapter[i].algo = s4985_algo + i;
 194                 s4985_adapter[i].dev.parent = nforce2_smbus->dev.parent;
 195         }
 196         s4985_algo[1].smbus_xfer = nforce2_access_virt1;
 197         s4985_algo[2].smbus_xfer = nforce2_access_virt2;
 198         s4985_algo[3].smbus_xfer = nforce2_access_virt3;
 199         s4985_algo[4].smbus_xfer = nforce2_access_virt4;
 200
 201         /* Register virtual adapters */
 202         for (i = 0; i < 5; i++) {
 203                 error = i2c_add_adapter(s4985_adapter + i);
 204                 if (error) {
 205                         printk(KERN_ERR "i2c-nforce2-s4985: "
 206                                "Virtual adapter %d registration "
 207                                "failed, module not inserted\n", i);
 208                         for (i--; i >= 0; i--)
 209                                 i2c_del_adapter(s4985_adapter + i);
 210                         goto ERROR3;
 211                 }
 212         }
 213
 214         return 0;
 215
 216 ERROR3:
 217         kfree(s4985_algo);
 218         s4985_algo = NULL;
 219 ERROR2:
 220         kfree(s4985_adapter);
 221         s4985_adapter = NULL;
 222 ERROR1:
 223         /* Restore physical bus */
 224         i2c_add_adapter(nforce2_smbus);
 225 ERROR0:
 226         return error;
 227 }
 228
 229 static void __exit nforce2_s4985_exit(void)
 230 {
 231         if (s4985_adapter) {
 232                 int i;
 233
 234                 for (i = 0; i < 5; i++)
 235                         i2c_del_adapter(s4985_adapter+i);
 236                 kfree(s4985_adapter);
 237                 s4985_adapter = NULL;
 238         }
 239         kfree(s4985_algo);
 240         s4985_algo = NULL;
 241
 242         /* Restore physical bus */
 243         if (i2c_add_adapter(nforce2_smbus))
 244                 printk(KERN_ERR "i2c-nforce2-s4985: "
 245                        "Physical bus restoration failed\n");
 246 }
 247
 248 MODULE_AUTHOR("Jean Delvare <jdelvare@suse.de>");
 249 MODULE_DESCRIPTION("S4985 SMBus multiplexing");
 250 MODULE_LICENSE("GPL");
 251
 252 module_init(nforce2_s4985_init);
 253 module_exit(nforce2_s4985_exit);