drivers/i2c/busses/i2c-acorn.c

   1 /*
   2  *  linux/drivers/acorn/char/i2c.c
   3  *
   4  *  Copyright (C) 2000 Russell King
   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 version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *  ARM IOC/IOMD i2c driver.
  11  *
  12  *  On Acorn machines, the following i2c devices are on the bus:
  13  *      - PCF8583 real time clock & static RAM
  14  */
  15 #include <linux/init.h>
  16 #include <linux/i2c.h>
  17 #include <linux/i2c-algo-bit.h>
  18 #include <linux/io.h>
  19
  20 #include <mach/hardware.h>
  21 #include <asm/hardware/ioc.h>
  22
  23 #define FORCE_ONES      0xdc
  24 #define SCL             0x02
  25 #define SDA             0x01
  26
  27 /*
  28  * We must preserve all non-i2c output bits in IOC_CONTROL.
  29  * Note also that we need to preserve the value of SCL and
  30  * SDA outputs as well (which may be different from the
  31  * values read back from IOC_CONTROL).
  32  */
  33 static u_int force_ones;
  34
  35 static void ioc_setscl(void *data, int state)
  36 {
  37         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  38         u_int ones = force_ones;
  39
  40         if (state)
  41                 ones |= SCL;
  42         else
  43                 ones &= ~SCL;
  44
  45         force_ones = ones;
  46
  47         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  48 }
  49
  50 static void ioc_setsda(void *data, int state)
  51 {
  52         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  53         u_int ones = force_ones;
  54
  55         if (state)
  56                 ones |= SDA;
  57         else
  58                 ones &= ~SDA;
  59
  60         force_ones = ones;
  61
  62         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  63 }
  64
  65 static int ioc_getscl(void *data)
  66 {
  67         return (ioc_readb(IOC_CONTROL) & SCL) != 0;
  68 }
  69
  70 static int ioc_getsda(void *data)
  71 {
  72         return (ioc_readb(IOC_CONTROL) & SDA) != 0;
  73 }
  74
  75 static struct i2c_algo_bit_data ioc_data = {
  76         .setsda         = ioc_setsda,
  77         .setscl         = ioc_setscl,
  78         .getsda         = ioc_getsda,
  79         .getscl         = ioc_getscl,
  80         .udelay         = 80,
  81         .timeout        = HZ,
  82 };
  83
  84 static struct i2c_adapter ioc_ops = {
  85         .nr                     = 0,
  86         .algo_data              = &ioc_data,
  87 };
  88
  89 static int __init i2c_ioc_init(void)
  90 {
  91         force_ones = FORCE_ONES | SCL | SDA;
  92
  93         return i2c_bit_add_numbered_bus(&ioc_ops);
  94 }
  95
  96 module_init(i2c_ioc_init);