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); 97