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 <khali@linux-fr.org>
   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         error = i2c_del_adapter(nforce2_smbus);
 168         if (error) {
 169                 dev_err(&nforce2_smbus->dev, "Physical bus removal failed\n");
 170                 goto ERROR0;
 171         }
 172
 173         printk(KERN_INFO "Enabling SMBus multiplexing for Tyan S4985\n");
 174         /* Define the 5 virtual adapters and algorithms structures */
 175         s4985_adapter = kzalloc(5 * sizeof(struct i2c_adapter), GFP_KERNEL);
 176         if (!s4985_adapter) {
 177                 error = -ENOMEM;
 178                 goto ERROR1;
 179         }
 180         s4985_algo = kzalloc(5 * sizeof(struct i2c_algorithm), GFP_KERNEL);
 181         if (!s4985_algo) {
 182                 error = -ENOMEM;
 183                 goto ERROR2;
 184         }
 185
 186         /* Fill in the new structures */
 187         s4985_algo[0] = *(nforce2_smbus->algo);
 188         s4985_algo[0].smbus_xfer = nforce2_access_virt0;
 189         s4985_adapter[0] = *nforce2_smbus;
 190         s4985_adapter[0].algo = s4985_algo;
 191         s4985_adapter[0].dev.parent = nforce2_smbus->dev.parent;
 192         for (i = 1; i < 5; i++) {
 193                 s4985_algo[i] = *(nforce2_smbus->algo);
 194                 s4985_adapter[i] = *nforce2_smbus;
 195                 snprintf(s4985_adapter[i].name, sizeof(s4985_adapter[i].name),
 196                          "SMBus nForce2 adapter (CPU%d)", i - 1);
 197                 s4985_adapter[i].algo = s4985_algo + i;
 198                 s4985_adapter[i].dev.parent = nforce2_smbus->dev.parent;
 199         }
 200         s4985_algo[1].smbus_xfer = nforce2_access_virt1;
 201         s4985_algo[2].smbus_xfer = nforce2_access_virt2;
 202         s4985_algo[3].smbus_xfer = nforce2_access_virt3;
 203         s4985_algo[4].smbus_xfer = nforce2_access_virt4;
 204
 205         /* Register virtual adapters */
 206         for (i = 0; i < 5; i++) {
 207                 error = i2c_add_adapter(s4985_adapter + i);
 208                 if (error) {
 209                         printk(KERN_ERR "i2c-nforce2-s4985: "
 210                                "Virtual adapter %d registration "
 211                                "failed, module not inserted\n", i);
 212                         for (i--; i >= 0; i--)
 213                                 i2c_del_adapter(s4985_adapter + i);
 214                         goto ERROR3;
 215                 }
 216         }
 217
 218         return 0;
 219
 220 ERROR3:
 221         kfree(s4985_algo);
 222         s4985_algo = NULL;
 223 ERROR2:
 224         kfree(s4985_adapter);
 225         s4985_adapter = NULL;
 226 ERROR1:
 227         /* Restore physical bus */
 228         i2c_add_adapter(nforce2_smbus);
 229 ERROR0:
 230         return error;
 231 }
 232
 233 static void __exit nforce2_s4985_exit(void)
 234 {
 235         if (s4985_adapter) {
 236                 int i;
 237
 238                 for (i = 0; i < 5; i++)
 239                         i2c_del_adapter(s4985_adapter+i);
 240                 kfree(s4985_adapter);
 241                 s4985_adapter = NULL;
 242         }
 243         kfree(s4985_algo);
 244         s4985_algo = NULL;
 245
 246         /* Restore physical bus */
 247         if (i2c_add_adapter(nforce2_smbus))
 248                 printk(KERN_ERR "i2c-nforce2-s4985: "
 249                        "Physical bus restoration failed\n");
 250 }
 251
 252 MODULE_AUTHOR("Jean Delvare <khali@linux-fr.org>");
 253 MODULE_DESCRIPTION("S4985 SMBus multiplexing");
 254 MODULE_LICENSE("GPL");
 255
 256 module_init(nforce2_s4985_init);
 257 module_exit(nforce2_s4985_exit);