drivers/i2c/algos/i2c-algo-sgi.c

   1 /*
   2  * i2c-algo-sgi.c: i2c driver algorithms for SGI adapters.
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License version 2 as published by the Free Software Foundation.
   6  *
   7  * Copyright (C) 2003 Ladislav Michl <ladis@linux-mips.org>
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/errno.h>
  14 #include <linux/delay.h>
  15
  16 #include <linux/i2c.h>
  17 #include <linux/i2c-algo-sgi.h>
  18
  19
  20 #define SGI_I2C_FORCE_IDLE      (0 << 0)
  21 #define SGI_I2C_NOT_IDLE        (1 << 0)
  22 #define SGI_I2C_WRITE           (0 << 1)
  23 #define SGI_I2C_READ            (1 << 1)
  24 #define SGI_I2C_RELEASE_BUS     (0 << 2)
  25 #define SGI_I2C_HOLD_BUS        (1 << 2)
  26 #define SGI_I2C_XFER_DONE       (0 << 4)
  27 #define SGI_I2C_XFER_BUSY       (1 << 4)
  28 #define SGI_I2C_ACK             (0 << 5)
  29 #define SGI_I2C_NACK            (1 << 5)
  30 #define SGI_I2C_BUS_OK          (0 << 7)
  31 #define SGI_I2C_BUS_ERR         (1 << 7)
  32
  33 #define get_control()           adap->getctrl(adap->data)
  34 #define set_control(val)        adap->setctrl(adap->data, val)
  35 #define read_data()             adap->rdata(adap->data)
  36 #define write_data(val)         adap->wdata(adap->data, val)
  37
  38
  39 static int wait_xfer_done(struct i2c_algo_sgi_data *adap)
  40 {
  41         int i;
  42
  43         for (i = 0; i < adap->xfer_timeout; i++) {
  44                 if ((get_control() & SGI_I2C_XFER_BUSY) == 0)
  45                         return 0;
  46                 udelay(1);
  47         }
  48
  49         return -ETIMEDOUT;
  50 }
  51
  52 static int wait_ack(struct i2c_algo_sgi_data *adap)
  53 {
  54         int i;
  55
  56         if (wait_xfer_done(adap))
  57                 return -ETIMEDOUT;
  58         for (i = 0; i < adap->ack_timeout; i++) {
  59                 if ((get_control() & SGI_I2C_NACK) == 0)
  60                         return 0;
  61                 udelay(1);
  62         }
  63
  64         return -ETIMEDOUT;
  65 }
  66
  67 static int force_idle(struct i2c_algo_sgi_data *adap)
  68 {
  69         int i;
  70
  71         set_control(SGI_I2C_FORCE_IDLE);
  72         for (i = 0; i < adap->xfer_timeout; i++) {
  73                 if ((get_control() & SGI_I2C_NOT_IDLE) == 0)
  74                         goto out;
  75                 udelay(1);
  76         }
  77         return -ETIMEDOUT;
  78 out:
  79         if (get_control() & SGI_I2C_BUS_ERR)
  80                 return -EIO;
  81         return 0;
  82 }
  83
  84 static int do_address(struct i2c_algo_sgi_data *adap, unsigned int addr,
  85                       int rd)
  86 {
  87         if (rd)
  88                 set_control(SGI_I2C_NOT_IDLE);
  89         /* Check if bus is idle, eventually force it to do so */
  90         if (get_control() & SGI_I2C_NOT_IDLE)
  91                 if (force_idle(adap))
  92                         return -EIO;
  93         /* Write out the i2c chip address and specify operation */
  94         set_control(SGI_I2C_HOLD_BUS | SGI_I2C_WRITE | SGI_I2C_NOT_IDLE);
  95         if (rd)
  96                 addr |= 1;
  97         write_data(addr);
  98         if (wait_ack(adap))
  99                 return -EIO;
 100         return 0;
 101 }
 102
 103 static int i2c_read(struct i2c_algo_sgi_data *adap, unsigned char *buf,
 104                     unsigned int len)
 105 {
 106         int i;
 107
 108         set_control(SGI_I2C_HOLD_BUS | SGI_I2C_READ | SGI_I2C_NOT_IDLE);
 109         for (i = 0; i < len; i++) {
 110                 if (wait_xfer_done(adap))
 111                         return -EIO;
 112                 buf[i] = read_data();
 113         }
 114         set_control(SGI_I2C_RELEASE_BUS | SGI_I2C_FORCE_IDLE);
 115
 116         return 0;
 117
 118 }
 119
 120 static int i2c_write(struct i2c_algo_sgi_data *adap, unsigned char *buf,
 121                      unsigned int len)
 122 {
 123         int i;
 124
 125         /* We are already in write state */
 126         for (i = 0; i < len; i++) {
 127                 write_data(buf[i]);
 128                 if (wait_ack(adap))
 129                         return -EIO;
 130         }
 131         return 0;
 132 }
 133
 134 static int sgi_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg *msgs,
 135                     int num)
 136 {
 137         struct i2c_algo_sgi_data *adap = i2c_adap->algo_data;
 138         struct i2c_msg *p;
 139         int i, err = 0;
 140
 141         for (i = 0; !err && i < num; i++) {
 142                 p = &msgs[i];
 143                 err = do_address(adap, p->addr, p->flags & I2C_M_RD);
 144                 if (err || !p->len)
 145                         continue;
 146                 if (p->flags & I2C_M_RD)
 147                         err = i2c_read(adap, p->buf, p->len);
 148                 else
 149                         err = i2c_write(adap, p->buf, p->len);
 150         }
 151
 152         return (err < 0) ? err : i;
 153 }
 154
 155 static u32 sgi_func(struct i2c_adapter *adap)
 156 {
 157         return I2C_FUNC_SMBUS_EMUL;
 158 }
 159
 160 static const struct i2c_algorithm sgi_algo = {
 161         .master_xfer    = sgi_xfer,
 162         .functionality  = sgi_func,
 163 };
 164
 165 /*
 166  * registering functions to load algorithms at runtime
 167  */
 168 int i2c_sgi_add_bus(struct i2c_adapter *adap)
 169 {
 170         adap->algo = &sgi_algo;
 171
 172         return i2c_add_adapter(adap);
 173 }
 174
 175
 176 int i2c_sgi_del_bus(struct i2c_adapter *adap)
 177 {
 178         return i2c_del_adapter(adap);
 179 }
 180
 181 EXPORT_SYMBOL(i2c_sgi_add_bus);
 182 EXPORT_SYMBOL(i2c_sgi_del_bus);
 183
 184 MODULE_AUTHOR("Ladislav Michl <ladis@linux-mips.org>");
 185 MODULE_DESCRIPTION("I2C-Bus SGI algorithm");
 186 MODULE_LICENSE("GPL");