drivers/i2c/busses/i2c-at91.c

   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
  37 static struct clk *twi_clk;
  38 static 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  */
  47 static 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  */
  78 static 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
  89 static 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
 108 static 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 separate
 139  * i2c message.
 140  * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
 141  */
 142 static 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  */
 181 static u32 at91_func(struct i2c_adapter *adapter)
 182 {
 183         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 184 }
 185
 186 static struct i2c_algorithm at91_algorithm = {
 187         .master_xfer    = at91_xfer,
 188         .functionality  = at91_func,
 189 };
 190
 191 /*
 192  * Main initialization routine.
 193  */
 194 static 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
 247 fail3:
 248         platform_set_drvdata(pdev, NULL);
 249         kfree(adapter);
 250         clk_disable(twi_clk);
 251 fail2:
 252         clk_put(twi_clk);
 253 fail1:
 254         iounmap(twi_base);
 255 fail0:
 256         release_mem_region(res->start, res->end - res->start + 1);
 257
 258         return rc;
 259 }
 260
 261 static 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
 284 static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
 285 {
 286         clk_disable(twi_clk);
 287         return 0;
 288 }
 289
 290 static 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 */
 301 MODULE_ALIAS("platform:at91_i2c");
 302
 303 static 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
 314 static int __init at91_i2c_init(void)
 315 {
 316         return platform_driver_register(&at91_i2c_driver);
 317 }
 318
 319 static void __exit at91_i2c_exit(void)
 320 {
 321         platform_driver_unregister(&at91_i2c_driver);
 322 }
 323
 324 module_init(at91_i2c_init);
 325 module_exit(at91_i2c_exit);
 326
 327 MODULE_AUTHOR("Rick Bronson");
 328 MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
 329 MODULE_LICENSE("GPL");