1/* 2 * i2c-algo-sgi.c: i2c driver algorithm used by the VINO (SGI Indy) and 3 * MACE (SGI O2) chips. 4 * 5 * This file is subject to the terms and conditions of the GNU General Public 6 * License version 2 as published by the Free Software Foundation. 7 * 8 * Copyright (C) 2003 Ladislav Michl <ladis@linux-mips.org> 9 */ 10 11#include <linux/kernel.h> 12#include <linux/module.h> 13#include <linux/init.h> 14#include <linux/errno.h> 15#include <linux/delay.h> 16 17#include <linux/i2c.h> 18#include <linux/i2c-algo-sgi.h> 19 20 21#define SGI_I2C_FORCE_IDLE (0 << 0) 22#define SGI_I2C_NOT_IDLE (1 << 0) 23#define SGI_I2C_WRITE (0 << 1) 24#define SGI_I2C_READ (1 << 1) 25#define SGI_I2C_RELEASE_BUS (0 << 2) 26#define SGI_I2C_HOLD_BUS (1 << 2) 27#define SGI_I2C_XFER_DONE (0 << 4) 28#define SGI_I2C_XFER_BUSY (1 << 4) 29#define SGI_I2C_ACK (0 << 5) 30#define SGI_I2C_NACK (1 << 5) 31#define SGI_I2C_BUS_OK (0 << 7) 32#define SGI_I2C_BUS_ERR (1 << 7) 33 34#define get_control() adap->getctrl(adap->data) 35#define set_control(val) adap->setctrl(adap->data, val) 36#define read_data() adap->rdata(adap->data) 37#define write_data(val) adap->wdata(adap->data, val) 38 39 40static int wait_xfer_done(struct i2c_algo_sgi_data *adap) 41{ 42 int i; 43 44 for (i = 0; i < adap->xfer_timeout; i++) { 45 if ((get_control() & SGI_I2C_XFER_BUSY) == 0) 46 return 0; 47 udelay(1); 48 } 49 50 return -ETIMEDOUT; 51} 52 53static int wait_ack(struct i2c_algo_sgi_data *adap) 54{ 55 int i; 56 57 if (wait_xfer_done(adap)) 58 return -ETIMEDOUT; 59 for (i = 0; i < adap->ack_timeout; i++) { 60 if ((get_control() & SGI_I2C_NACK) == 0) 61 return 0; 62 udelay(1); 63 } 64 65 return -ETIMEDOUT; 66} 67 68static int force_idle(struct i2c_algo_sgi_data *adap) 69{ 70 int i; 71 72 set_control(SGI_I2C_FORCE_IDLE); 73 for (i = 0; i < adap->xfer_timeout; i++) { 74 if ((get_control() & SGI_I2C_NOT_IDLE) == 0) 75 goto out; 76 udelay(1); 77 } 78 return -ETIMEDOUT; 79out: 80 if (get_control() & SGI_I2C_BUS_ERR) 81 return -EIO; 82 return 0; 83} 84 85static int do_address(struct i2c_algo_sgi_data *adap, unsigned int addr, 86 int rd) 87{ 88 if (rd) 89 set_control(SGI_I2C_NOT_IDLE); 90 /* Check if bus is idle, eventually force it to do so */ 91 if (get_control() & SGI_I2C_NOT_IDLE) 92 if (force_idle(adap)) 93 return -EIO; 94 /* Write out the i2c chip address and specify operation */ 95 set_control(SGI_I2C_HOLD_BUS | SGI_I2C_WRITE | SGI_I2C_NOT_IDLE); 96 if (rd) 97 addr |= 1; 98 write_data(addr); 99 if (wait_ack(adap)) 100 return -EIO; 101 return 0; 102} 103 104static int i2c_read(struct i2c_algo_sgi_data *adap, unsigned char *buf, 105 unsigned int len) 106{ 107 int i; 108 109 set_control(SGI_I2C_HOLD_BUS | SGI_I2C_READ | SGI_I2C_NOT_IDLE); 110 for (i = 0; i < len; i++) { 111 if (wait_xfer_done(adap)) 112 return -EIO; 113 buf[i] = read_data(); 114 } 115 set_control(SGI_I2C_RELEASE_BUS | SGI_I2C_FORCE_IDLE); 116 117 return 0; 118 119} 120 121static int i2c_write(struct i2c_algo_sgi_data *adap, unsigned char *buf, 122 unsigned int len) 123{ 124 int i; 125 126 /* We are already in write state */ 127 for (i = 0; i < len; i++) { 128 write_data(buf[i]); 129 if (wait_ack(adap)) 130 return -EIO; 131 } 132 return 0; 133} 134 135static int sgi_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg *msgs, 136 int num) 137{ 138 struct i2c_algo_sgi_data *adap = i2c_adap->algo_data; 139 struct i2c_msg *p; 140 int i, err = 0; 141 142 for (i = 0; !err && i < num; i++) { 143 p = &msgs[i]; 144 err = do_address(adap, p->addr, p->flags & I2C_M_RD); 145 if (err || !p->len) 146 continue; 147 if (p->flags & I2C_M_RD) 148 err = i2c_read(adap, p->buf, p->len); 149 else 150 err = i2c_write(adap, p->buf, p->len); 151 } 152 153 return (err < 0) ? err : i; 154} 155 156static u32 sgi_func(struct i2c_adapter *adap) 157{ 158 return I2C_FUNC_SMBUS_EMUL; 159} 160 161static const struct i2c_algorithm sgi_algo = { 162 .master_xfer = sgi_xfer, 163 .functionality = sgi_func, 164}; 165 166/* 167 * registering functions to load algorithms at runtime 168 */ 169int i2c_sgi_add_bus(struct i2c_adapter *adap) 170{ 171 adap->algo = &sgi_algo; 172 173 return i2c_add_adapter(adap); 174} 175EXPORT_SYMBOL(i2c_sgi_add_bus); 176 177MODULE_AUTHOR("Ladislav Michl <ladis@linux-mips.org>"); 178MODULE_DESCRIPTION("I2C-Bus SGI algorithm"); 179MODULE_LICENSE("GPL"); 180