drivers/i2c/busses/i2c-acorn.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  ARM IOC/IOMD i2c driver.
   4  *
   5  *  Copyright (C) 2000 Russell King
   6  *
   7  *  On Acorn machines, the following i2c devices are on the bus:
   8  *      - PCF8583 real time clock & static RAM
   9  */
  10 #include <linux/module.h>
  11 #include <linux/i2c.h>
  12 #include <linux/i2c-algo-bit.h>
  13 #include <linux/io.h>
  14
  15 #include <mach/hardware.h>
  16 #include <asm/hardware/ioc.h>
  17
  18 #define FORCE_ONES      0xdc
  19 #define SCL             0x02
  20 #define SDA             0x01
  21
  22 /*
  23  * We must preserve all non-i2c output bits in IOC_CONTROL.
  24  * Note also that we need to preserve the value of SCL and
  25  * SDA outputs as well (which may be different from the
  26  * values read back from IOC_CONTROL).
  27  */
  28 static u_int force_ones;
  29
  30 static void ioc_setscl(void *data, int state)
  31 {
  32         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  33         u_int ones = force_ones;
  34
  35         if (state)
  36                 ones |= SCL;
  37         else
  38                 ones &= ~SCL;
  39
  40         force_ones = ones;
  41
  42         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  43 }
  44
  45 static void ioc_setsda(void *data, int state)
  46 {
  47         u_int ioc_control = ioc_readb(IOC_CONTROL) & ~(SCL | SDA);
  48         u_int ones = force_ones;
  49
  50         if (state)
  51                 ones |= SDA;
  52         else
  53                 ones &= ~SDA;
  54
  55         force_ones = ones;
  56
  57         ioc_writeb(ioc_control | ones, IOC_CONTROL);
  58 }
  59
  60 static int ioc_getscl(void *data)
  61 {
  62         return (ioc_readb(IOC_CONTROL) & SCL) != 0;
  63 }
  64
  65 static int ioc_getsda(void *data)
  66 {
  67         return (ioc_readb(IOC_CONTROL) & SDA) != 0;
  68 }
  69
  70 static struct i2c_algo_bit_data ioc_data = {
  71         .setsda         = ioc_setsda,
  72         .setscl         = ioc_setscl,
  73         .getsda         = ioc_getsda,
  74         .getscl         = ioc_getscl,
  75         .udelay         = 80,
  76         .timeout        = HZ,
  77 };
  78
  79 static struct i2c_adapter ioc_ops = {
  80         .nr                     = 0,
  81         .name                   = "ioc",
  82         .algo_data              = &ioc_data,
  83 };
  84
  85 static int __init i2c_ioc_init(void)
  86 {
  87         force_ones = FORCE_ONES | SCL | SDA;
  88
  89         return i2c_bit_add_numbered_bus(&ioc_ops);
  90 }
  91
  92 module_init(i2c_ioc_init);
  93
  94 MODULE_AUTHOR("Russell King <linux@armlinux.org.uk>");
  95 MODULE_DESCRIPTION("ARM IOC/IOMD i2c driver");
  96 MODULE_LICENSE("GPL v2");