1/* 2 i2c Support for Atmel's AT91 Two-Wire Interface (TWI) 3 4 Copyright (C) 2004 Rick Bronson 5 Converted to 2.6 by Andrew Victor <andrew@sanpeople.com> 6 7 Borrowed heavily from original work by: 8 Copyright (C) 2000 Philip Edelbrock <phil@stimpy.netroedge.com> 9 10 This program is free software; you can redistribute it and/or modify 11 it under the terms of the GNU General Public License as published by 12 the Free Software Foundation; either version 2 of the License, or 13 (at your option) any later version. 14*/ 15 16#include <linux/module.h> 17#include <linux/version.h> 18#include <linux/kernel.h> 19#include <linux/err.h> 20#include <linux/slab.h> 21#include <linux/types.h> 22#include <linux/delay.h> 23#include <linux/i2c.h> 24#include <linux/init.h> 25#include <linux/clk.h> 26#include <linux/platform_device.h> 27 28#include <asm/io.h> 29 30#include <asm/arch/at91_twi.h> 31#include <asm/arch/board.h> 32#include <asm/arch/cpu.h> 33 34#define TWI_CLOCK 100000 /* Hz. max 400 Kbits/sec */ 35 36 37static struct clk *twi_clk; 38static void __iomem *twi_base; 39 40#define at91_twi_read(reg) __raw_readl(twi_base + (reg)) 41#define at91_twi_write(reg, val) __raw_writel((val), twi_base + (reg)) 42 43 44/* 45 * Initialize the TWI hardware registers. 46 */ 47static void __devinit at91_twi_hwinit(void) 48{ 49 unsigned long cdiv, ckdiv; 50 51 at91_twi_write(AT91_TWI_IDR, 0xffffffff); /* Disable all interrupts */ 52 at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST); /* Reset peripheral */ 53 at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN); /* Set Master mode */ 54 55 /* Calcuate clock dividers */ 56 cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3; 57 cdiv = cdiv + 1; /* round up */ 58 ckdiv = 0; 59 while (cdiv > 255) { 60 ckdiv++; 61 cdiv = cdiv >> 1; 62 } 63 64 if (cpu_is_at91rm9200()) { /* AT91RM9200 Errata #22 */ 65 if (ckdiv > 5) { 66 printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n"); 67 ckdiv = 5; 68 } 69 } 70 71 at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv); 72} 73 74/* 75 * Poll the i2c status register until the specified bit is set. 76 * Returns 0 if timed out (100 msec). 77 */ 78static short at91_poll_status(unsigned long bit) 79{ 80 int loop_cntr = 10000; 81 82 do { 83 udelay(10); 84 } while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0)); 85 86 return (loop_cntr > 0); 87} 88 89static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length) 90{ 91 /* Send Start */ 92 at91_twi_write(AT91_TWI_CR, AT91_TWI_START); 93 94 /* Read data */ 95 while (length--) { 96 if (!length) /* need to send Stop before reading last byte */ 97 at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP); 98 if (!at91_poll_status(AT91_TWI_RXRDY)) { 99 dev_dbg(&adap->dev, "RXRDY timeout\n"); 100 return -ETIMEDOUT; 101 } 102 *buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff); 103 } 104 105 return 0; 106} 107 108static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length) 109{ 110 /* Load first byte into transmitter */ 111 at91_twi_write(AT91_TWI_THR, *buf++); 112 113 /* Send Start */ 114 at91_twi_write(AT91_TWI_CR, AT91_TWI_START); 115 116 do { 117 if (!at91_poll_status(AT91_TWI_TXRDY)) { 118 dev_dbg(&adap->dev, "TXRDY timeout\n"); 119 return -ETIMEDOUT; 120 } 121 122 length--; /* byte was transmitted */ 123 124 if (length > 0) /* more data to send? */ 125 at91_twi_write(AT91_TWI_THR, *buf++); 126 } while (length); 127 128 /* Send Stop */ 129 at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP); 130 131 return 0; 132} 133 134/* 135 * Generic i2c master transfer entrypoint. 136 * 137 * Note: We do not use Atmel's feature of storing the "internal device address". 138 * Instead the "internal device address" has to be written using a seperate 139 * i2c message. 140 * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html 141 */ 142static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num) 143{ 144 int i, ret; 145 146 dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num); 147 148 for (i = 0; i < num; i++) { 149 dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i, 150 pmsg->flags & I2C_M_RD ? "read" : "writ", 151 pmsg->len, pmsg->len > 1 ? "s" : "", 152 pmsg->flags & I2C_M_RD ? "from" : "to", pmsg->addr); 153 154 at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16) 155 | ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0)); 156 157 if (pmsg->len && pmsg->buf) { /* sanity check */ 158 if (pmsg->flags & I2C_M_RD) 159 ret = xfer_read(adap, pmsg->buf, pmsg->len); 160 else 161 ret = xfer_write(adap, pmsg->buf, pmsg->len); 162 163 if (ret) 164 return ret; 165 166 /* Wait until transfer is finished */ 167 if (!at91_poll_status(AT91_TWI_TXCOMP)) { 168 dev_dbg(&adap->dev, "TXCOMP timeout\n"); 169 return -ETIMEDOUT; 170 } 171 } 172 dev_dbg(&adap->dev, "transfer complete\n"); 173 pmsg++; /* next message */ 174 } 175 return i; 176} 177 178/* 179 * Return list of supported functionality. 180 */ 181static u32 at91_func(struct i2c_adapter *adapter) 182{ 183 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 184} 185 186static struct i2c_algorithm at91_algorithm = { 187 .master_xfer = at91_xfer, 188 .functionality = at91_func, 189}; 190 191/* 192 * Main initialization routine. 193 */ 194static int __devinit at91_i2c_probe(struct platform_device *pdev) 195{ 196 struct i2c_adapter *adapter; 197 struct resource *res; 198 int rc; 199 200 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 201 if (!res) 202 return -ENXIO; 203 204 if (!request_mem_region(res->start, res->end - res->start + 1, "at91_i2c")) 205 return -EBUSY; 206 207 twi_base = ioremap(res->start, res->end - res->start + 1); 208 if (!twi_base) { 209 rc = -ENOMEM; 210 goto fail0; 211 } 212 213 twi_clk = clk_get(NULL, "twi_clk"); 214 if (IS_ERR(twi_clk)) { 215 dev_err(&pdev->dev, "no clock defined\n"); 216 rc = -ENODEV; 217 goto fail1; 218 } 219 220 adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL); 221 if (adapter == NULL) { 222 dev_err(&pdev->dev, "can't allocate inteface!\n"); 223 rc = -ENOMEM; 224 goto fail2; 225 } 226 sprintf(adapter->name, "AT91"); 227 adapter->algo = &at91_algorithm; 228 adapter->class = I2C_CLASS_HWMON; 229 adapter->dev.parent = &pdev->dev; 230 /* adapter->id == 0 ... only one TWI controller for now */ 231 232 platform_set_drvdata(pdev, adapter); 233 234 clk_enable(twi_clk); /* enable peripheral clock */ 235 at91_twi_hwinit(); /* initialize TWI controller */ 236 237 rc = i2c_add_numbered_adapter(adapter); 238 if (rc) { 239 dev_err(&pdev->dev, "Adapter %s registration failed\n", 240 adapter->name); 241 goto fail3; 242 } 243 244 dev_info(&pdev->dev, "AT91 i2c bus driver.\n"); 245 return 0; 246 247fail3: 248 platform_set_drvdata(pdev, NULL); 249 kfree(adapter); 250 clk_disable(twi_clk); 251fail2: 252 clk_put(twi_clk); 253fail1: 254 iounmap(twi_base); 255fail0: 256 release_mem_region(res->start, res->end - res->start + 1); 257 258 return rc; 259} 260 261static int __devexit at91_i2c_remove(struct platform_device *pdev) 262{ 263 struct i2c_adapter *adapter = platform_get_drvdata(pdev); 264 struct resource *res; 265 int rc; 266 267 rc = i2c_del_adapter(adapter); 268 platform_set_drvdata(pdev, NULL); 269 270 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 271 iounmap(twi_base); 272 release_mem_region(res->start, res->end - res->start + 1); 273 274 clk_disable(twi_clk); /* disable peripheral clock */ 275 clk_put(twi_clk); 276 277 return rc; 278} 279 280#ifdef CONFIG_PM 281 282/* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */ 283 284static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg) 285{ 286 clk_disable(twi_clk); 287 return 0; 288} 289 290static int at91_i2c_resume(struct platform_device *pdev) 291{ 292 return clk_enable(twi_clk); 293} 294 295#else 296#define at91_i2c_suspend NULL 297#define at91_i2c_resume NULL 298#endif 299 300/* work with "modprobe at91_i2c" from hotplugging or coldplugging */ 301MODULE_ALIAS("at91_i2c"); 302 303static struct platform_driver at91_i2c_driver = { 304 .probe = at91_i2c_probe, 305 .remove = __devexit_p(at91_i2c_remove), 306 .suspend = at91_i2c_suspend, 307 .resume = at91_i2c_resume, 308 .driver = { 309 .name = "at91_i2c", 310 .owner = THIS_MODULE, 311 }, 312}; 313 314static int __init at91_i2c_init(void) 315{ 316 return platform_driver_register(&at91_i2c_driver); 317} 318 319static void __exit at91_i2c_exit(void) 320{ 321 platform_driver_unregister(&at91_i2c_driver); 322} 323 324module_init(at91_i2c_init); 325module_exit(at91_i2c_exit); 326 327MODULE_AUTHOR("Rick Bronson"); 328MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91"); 329MODULE_LICENSE("GPL"); 330