drivers/i2c/busses/i2c-acorn.c

   1 /*
   2  *  ARM IOC/IOMD i2c driver.
   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  *  On Acorn machines, the following i2c devices are on the bus:
  11  *      - PCF8583 real time clock & static RAM
  12  */
  13 #include <linux/module.h>
  14 #include <linux/i2c.h>
  15 #include <linux/i2c-algo-bit.h>
  16 #include <linux/io.h>
  17
  18 #include <mach/hardware.h>
  19 #include <asm/hardware/ioc.h>
  20
  21 #define FORCE_ONES      0xdc
  22 #define SCL             0x02
  23 #define SDA             0x01
  24
  25 /*
  26  * We must preserve all non-i2c output bits in IOC_CONTROL.
  27  * Note also that we need to preserve the value of SCL and
  28  * SDA outputs as well (which may be different from the
  29  * values read back from IOC_CONTROL).
  30  */
  31 static u_int force_ones;
  32
  33 static void ioc_setscl(void *data, int state)
  34 {
  35         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  36         u_int ones = force_ones;
  37
  38         if (state)
  39                 ones |= SCL;
  40         else
  41                 ones &= ~SCL;
  42
  43         force_ones = ones;
  44
  45         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  46 }
  47
  48 static void ioc_setsda(void *data, int state)
  49 {
  50         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  51         u_int ones = force_ones;
  52
  53         if (state)
  54                 ones |= SDA;
  55         else
  56                 ones &= ~SDA;
  57
  58         force_ones = ones;
  59
  60         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  61 }
  62
  63 static int ioc_getscl(void *data)
  64 {
  65         return (ioc_readb(IOC_CONTROL) & SCL) != 0;
  66 }
  67
  68 static int ioc_getsda(void *data)
  69 {
  70         return (ioc_readb(IOC_CONTROL) & SDA) != 0;
  71 }
  72
  73 static struct i2c_algo_bit_data ioc_data = {
  74         .setsda         = ioc_setsda,
  75         .setscl         = ioc_setscl,
  76         .getsda         = ioc_getsda,
  77         .getscl         = ioc_getscl,
  78         .udelay         = 80,
  79         .timeout        = HZ,
  80 };
  81
  82 static struct i2c_adapter ioc_ops = {
  83         .nr                     = 0,
  84         .algo_data              = &ioc_data,
  85 };
  86
  87 static int __init i2c_ioc_init(void)
  88 {
  89         force_ones = FORCE_ONES | SCL | SDA;
  90
  91         return i2c_bit_add_numbered_bus(&ioc_ops);
  92 }
  93
  94 module_init(i2c_ioc_init);
  95
  96 MODULE_AUTHOR("Russell King <linux@armlinux.org.uk>");
  97 MODULE_DESCRIPTION("ARM IOC/IOMD i2c driver");
  98 MODULE_LICENSE("GPL v2");