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
  19 #include <asm/hardware.h>
  20 #include <asm/io.h>
  21 #include <asm/hardware/ioc.h>
  22 #include <asm/system.h>
  23
  24 #define FORCE_ONES      0xdc
  25 #define SCL             0x02
  26 #define SDA             0x01
  27
  28 /*
  29  * We must preserve all non-i2c output bits in IOC_CONTROL.
  30  * Note also that we need to preserve the value of SCL and
  31  * SDA outputs as well (which may be different from the
  32  * values read back from IOC_CONTROL).
  33  */
  34 static u_int force_ones;
  35
  36 static void ioc_setscl(void *data, int state)
  37 {
  38         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  39         u_int ones = force_ones;
  40
  41         if (state)
  42                 ones |= SCL;
  43         else
  44                 ones &= ~SCL;
  45
  46         force_ones = ones;
  47
  48         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  49 }
  50
  51 static void ioc_setsda(void *data, int state)
  52 {
  53         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  54         u_int ones = force_ones;
  55
  56         if (state)
  57                 ones |= SDA;
  58         else
  59                 ones &= ~SDA;
  60
  61         force_ones = ones;
  62
  63         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  64 }
  65
  66 static int ioc_getscl(void *data)
  67 {
  68         return (ioc_readb(IOC_CONTROL) & SCL) != 0;
  69 }
  70
  71 static int ioc_getsda(void *data)
  72 {
  73         return (ioc_readb(IOC_CONTROL) & SDA) != 0;
  74 }
  75
  76 static struct i2c_algo_bit_data ioc_data = {
  77         .setsda         = ioc_setsda,
  78         .setscl         = ioc_setscl,
  79         .getsda         = ioc_getsda,
  80         .getscl         = ioc_getscl,
  81         .udelay         = 80,
  82         .timeout        = 100
  83 };
  84
  85 static struct i2c_adapter ioc_ops = {
  86         .id                     = I2C_HW_B_IOC,
  87         .algo_data              = &ioc_data,
  88 };
  89
  90 static int __init i2c_ioc_init(void)
  91 {
  92         force_ones = FORCE_ONES | SCL | SDA;
  93
  94         return i2c_bit_add_bus(&ioc_ops);
  95 }
  96
  97 __initcall(i2c_ioc_init);