drivers/i2c/busses/i2c-bcm2835.c

   1 /*
   2  * BCM2835 master mode driver
   3  *
   4  * This software is licensed under the terms of the GNU General Public
   5  * License version 2, as published by the Free Software Foundation, and
   6  * may be copied, distributed, and modified under those terms.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <linux/clk.h>
  15 #include <linux/completion.h>
  16 #include <linux/err.h>
  17 #include <linux/i2c.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/io.h>
  20 #include <linux/module.h>
  21 #include <linux/platform_device.h>
  22 #include <linux/slab.h>
  23
  24 #define BCM2835_I2C_C           0x0
  25 #define BCM2835_I2C_S           0x4
  26 #define BCM2835_I2C_DLEN        0x8
  27 #define BCM2835_I2C_A           0xc
  28 #define BCM2835_I2C_FIFO        0x10
  29 #define BCM2835_I2C_DIV         0x14
  30 #define BCM2835_I2C_DEL         0x18
  31 #define BCM2835_I2C_CLKT        0x1c
  32
  33 #define BCM2835_I2C_C_READ      BIT(0)
  34 #define BCM2835_I2C_C_CLEAR     BIT(4) /* bits 4 and 5 both clear */
  35 #define BCM2835_I2C_C_ST        BIT(7)
  36 #define BCM2835_I2C_C_INTD      BIT(8)
  37 #define BCM2835_I2C_C_INTT      BIT(9)
  38 #define BCM2835_I2C_C_INTR      BIT(10)
  39 #define BCM2835_I2C_C_I2CEN     BIT(15)
  40
  41 #define BCM2835_I2C_S_TA        BIT(0)
  42 #define BCM2835_I2C_S_DONE      BIT(1)
  43 #define BCM2835_I2C_S_TXW       BIT(2)
  44 #define BCM2835_I2C_S_RXR       BIT(3)
  45 #define BCM2835_I2C_S_TXD       BIT(4)
  46 #define BCM2835_I2C_S_RXD       BIT(5)
  47 #define BCM2835_I2C_S_TXE       BIT(6)
  48 #define BCM2835_I2C_S_RXF       BIT(7)
  49 #define BCM2835_I2C_S_ERR       BIT(8)
  50 #define BCM2835_I2C_S_CLKT      BIT(9)
  51 #define BCM2835_I2C_S_LEN       BIT(10) /* Fake bit for SW error reporting */
  52
  53 #define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
  54
  55 struct bcm2835_i2c_dev {
  56         struct device *dev;
  57         void __iomem *regs;
  58         struct clk *clk;
  59         int irq;
  60         struct i2c_adapter adapter;
  61         struct completion completion;
  62         u32 msg_err;
  63         u8 *msg_buf;
  64         size_t msg_buf_remaining;
  65 };
  66
  67 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
  68                                       u32 reg, u32 val)
  69 {
  70         writel(val, i2c_dev->regs + reg);
  71 }
  72
  73 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
  74 {
  75         return readl(i2c_dev->regs + reg);
  76 }
  77
  78 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
  79 {
  80         u32 val;
  81
  82         while (i2c_dev->msg_buf_remaining) {
  83                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
  84                 if (!(val & BCM2835_I2C_S_TXD))
  85                         break;
  86                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
  87                                    *i2c_dev->msg_buf);
  88                 i2c_dev->msg_buf++;
  89                 i2c_dev->msg_buf_remaining--;
  90         }
  91 }
  92
  93 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
  94 {
  95         u32 val;
  96
  97         while (i2c_dev->msg_buf_remaining) {
  98                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
  99                 if (!(val & BCM2835_I2C_S_RXD))
 100                         break;
 101                 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
 102                                                       BCM2835_I2C_FIFO);
 103                 i2c_dev->msg_buf++;
 104                 i2c_dev->msg_buf_remaining--;
 105         }
 106 }
 107
 108 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
 109 {
 110         struct bcm2835_i2c_dev *i2c_dev = data;
 111         u32 val, err;
 112
 113         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 114         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
 115
 116         err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
 117         if (err) {
 118                 i2c_dev->msg_err = err;
 119                 complete(&i2c_dev->completion);
 120                 return IRQ_HANDLED;
 121         }
 122
 123         if (val & BCM2835_I2C_S_RXD) {
 124                 bcm2835_drain_rxfifo(i2c_dev);
 125                 if (!(val & BCM2835_I2C_S_DONE))
 126                         return IRQ_HANDLED;
 127         }
 128
 129         if (val & BCM2835_I2C_S_DONE) {
 130                 if (i2c_dev->msg_buf_remaining)
 131                         i2c_dev->msg_err = BCM2835_I2C_S_LEN;
 132                 else
 133                         i2c_dev->msg_err = 0;
 134                 complete(&i2c_dev->completion);
 135                 return IRQ_HANDLED;
 136         }
 137
 138         if (val & BCM2835_I2C_S_TXD) {
 139                 bcm2835_fill_txfifo(i2c_dev);
 140                 return IRQ_HANDLED;
 141         }
 142
 143         return IRQ_NONE;
 144 }
 145
 146 static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
 147                                 struct i2c_msg *msg)
 148 {
 149         u32 c;
 150         int time_left;
 151
 152         i2c_dev->msg_buf = msg->buf;
 153         i2c_dev->msg_buf_remaining = msg->len;
 154         INIT_COMPLETION(i2c_dev->completion);
 155
 156         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 157
 158         if (msg->flags & I2C_M_RD) {
 159                 c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
 160         } else {
 161                 c = BCM2835_I2C_C_INTT;
 162                 bcm2835_fill_txfifo(i2c_dev);
 163         }
 164         c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;
 165
 166         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
 167         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
 168         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
 169
 170         time_left = wait_for_completion_timeout(&i2c_dev->completion,
 171                                                 BCM2835_I2C_TIMEOUT);
 172         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 173         if (!time_left) {
 174                 dev_err(i2c_dev->dev, "i2c transfer timed out\n");
 175                 return -ETIMEDOUT;
 176         }
 177
 178         if (likely(!i2c_dev->msg_err))
 179                 return 0;
 180
 181         if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
 182             (msg->flags & I2C_M_IGNORE_NAK))
 183                 return 0;
 184
 185         dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
 186
 187         if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
 188                 return -EREMOTEIO;
 189         else
 190                 return -EIO;
 191 }
 192
 193 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 194                             int num)
 195 {
 196         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
 197         int i;
 198         int ret = 0;
 199
 200         for (i = 0; i < num; i++) {
 201                 ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);
 202                 if (ret)
 203                         break;
 204         }
 205
 206         return ret ?: i;
 207 }
 208
 209 static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
 210 {
 211         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 212 }
 213
 214 static const struct i2c_algorithm bcm2835_i2c_algo = {
 215         .master_xfer    = bcm2835_i2c_xfer,
 216         .functionality  = bcm2835_i2c_func,
 217 };
 218
 219 static int bcm2835_i2c_probe(struct platform_device *pdev)
 220 {
 221         struct bcm2835_i2c_dev *i2c_dev;
 222         struct resource *mem, *requested, *irq;
 223         u32 bus_clk_rate, divider;
 224         int ret;
 225         struct i2c_adapter *adap;
 226
 227         i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
 228         if (!i2c_dev) {
 229                 dev_err(&pdev->dev, "Cannot allocate i2c_dev\n");
 230                 return -ENOMEM;
 231         }
 232         platform_set_drvdata(pdev, i2c_dev);
 233         i2c_dev->dev = &pdev->dev;
 234         init_completion(&i2c_dev->completion);
 235
 236         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 237         if (!mem) {
 238                 dev_err(&pdev->dev, "No mem resource\n");
 239                 return -ENODEV;
 240         }
 241
 242         requested = devm_request_mem_region(&pdev->dev, mem->start,
 243                                             resource_size(mem),
 244                                             dev_name(&pdev->dev));
 245         if (!requested) {
 246                 dev_err(&pdev->dev, "Could not claim register region\n");
 247                 return -EBUSY;
 248         }
 249
 250         i2c_dev->regs = devm_ioremap(&pdev->dev, mem->start,
 251                                      resource_size(mem));
 252         if (!i2c_dev->regs) {
 253                 dev_err(&pdev->dev, "Could not map registers\n");
 254                 return -ENOMEM;
 255         }
 256
 257         i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
 258         if (IS_ERR(i2c_dev->clk)) {
 259                 dev_err(&pdev->dev, "Could not get clock\n");
 260                 return PTR_ERR(i2c_dev->clk);
 261         }
 262
 263         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 264                                    &bus_clk_rate);
 265         if (ret < 0) {
 266                 dev_warn(&pdev->dev,
 267                          "Could not read clock-frequency property\n");
 268                 bus_clk_rate = 100000;
 269         }
 270
 271         divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
 272         /*
 273          * Per the datasheet, the register is always interpreted as an even
 274          * number, by rounding down. In other words, the LSB is ignored. So,
 275          * if the LSB is set, increment the divider to avoid any issue.
 276          */
 277         if (divider & 1)
 278                 divider++;
 279         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
 280
 281         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 282         if (!irq) {
 283                 dev_err(&pdev->dev, "No IRQ resource\n");
 284                 return -ENODEV;
 285         }
 286         i2c_dev->irq = irq->start;
 287
 288         ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
 289                           dev_name(&pdev->dev), i2c_dev);
 290         if (ret) {
 291                 dev_err(&pdev->dev, "Could not request IRQ\n");
 292                 return -ENODEV;
 293         }
 294
 295         adap = &i2c_dev->adapter;
 296         i2c_set_adapdata(adap, i2c_dev);
 297         adap->owner = THIS_MODULE;
 298         adap->class = I2C_CLASS_HWMON;
 299         strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
 300         adap->algo = &bcm2835_i2c_algo;
 301         adap->dev.parent = &pdev->dev;
 302
 303         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
 304
 305         ret = i2c_add_adapter(adap);
 306         if (ret)
 307                 free_irq(i2c_dev->irq, i2c_dev);
 308
 309         return ret;
 310 }
 311
 312 static int bcm2835_i2c_remove(struct platform_device *pdev)
 313 {
 314         struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 315
 316         free_irq(i2c_dev->irq, i2c_dev);
 317         i2c_del_adapter(&i2c_dev->adapter);
 318
 319         return 0;
 320 }
 321
 322 static const struct of_device_id bcm2835_i2c_of_match[] = {
 323         { .compatible = "brcm,bcm2835-i2c" },
 324         {},
 325 };
 326 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
 327
 328 static struct platform_driver bcm2835_i2c_driver = {
 329         .probe          = bcm2835_i2c_probe,
 330         .remove         = bcm2835_i2c_remove,
 331         .driver         = {
 332                 .name   = "i2c-bcm2835",
 333                 .owner  = THIS_MODULE,
 334                 .of_match_table = bcm2835_i2c_of_match,
 335         },
 336 };
 337 module_platform_driver(bcm2835_i2c_driver);
 338
 339 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 340 MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
 341 MODULE_LICENSE("GPL v2");
 342 MODULE_ALIAS("platform:i2c-bcm2835");