drivers/i2c/busses/i2c-riic.c

   1 /*
   2  * Renesas RIIC driver
   3  *
   4  * Copyright (C) 2013 Wolfram Sang <wsa@sang-engineering.com>
   5  * Copyright (C) 2013 Renesas Solutions Corp.
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published by
   9  * the Free Software Foundation.
  10  */
  11
  12 /*
  13  * This i2c core has a lot of interrupts, namely 8. We use their chaining as
  14  * some kind of state machine.
  15  *
  16  * 1) The main xfer routine kicks off a transmission by putting the start bit
  17  * (or repeated start) on the bus and enabling the transmit interrupt (TIE)
  18  * since we need to send the slave address + RW bit in every case.
  19  *
  20  * 2) TIE sends slave address + RW bit and selects how to continue.
  21  *
  22  * 3a) Write case: We keep utilizing TIE as long as we have data to send. If we
  23  * are done, we switch over to the transmission done interrupt (TEIE) and mark
  24  * the message as completed (includes sending STOP) there.
  25  *
  26  * 3b) Read case: We switch over to receive interrupt (RIE). One dummy read is
  27  * needed to start clocking, then we keep receiving until we are done. Note
  28  * that we use the RDRFS mode all the time, i.e. we ACK/NACK every byte by
  29  * writing to the ACKBT bit. I tried using the RDRFS mode only at the end of a
  30  * message to create the final NACK as sketched in the datasheet. This caused
  31  * some subtle races (when byte n was processed and byte n+1 was already
  32  * waiting), though, and I started with the safe approach.
  33  *
  34  * 4) If we got a NACK somewhere, we flag the error and stop the transmission
  35  * via NAKIE.
  36  *
  37  * Also check the comments in the interrupt routines for some gory details.
  38  */
  39
  40 #include <linux/clk.h>
  41 #include <linux/completion.h>
  42 #include <linux/err.h>
  43 #include <linux/i2c.h>
  44 #include <linux/interrupt.h>
  45 #include <linux/io.h>
  46 #include <linux/module.h>
  47 #include <linux/of.h>
  48 #include <linux/platform_device.h>
  49
  50 #define RIIC_ICCR1      0x00
  51 #define RIIC_ICCR2      0x04
  52 #define RIIC_ICMR1      0x08
  53 #define RIIC_ICMR3      0x10
  54 #define RIIC_ICSER      0x18
  55 #define RIIC_ICIER      0x1c
  56 #define RIIC_ICSR2      0x24
  57 #define RIIC_ICBRL      0x34
  58 #define RIIC_ICBRH      0x38
  59 #define RIIC_ICDRT      0x3c
  60 #define RIIC_ICDRR      0x40
  61
  62 #define ICCR1_ICE       0x80
  63 #define ICCR1_IICRST    0x40
  64 #define ICCR1_SOWP      0x10
  65
  66 #define ICCR2_BBSY      0x80
  67 #define ICCR2_SP        0x08
  68 #define ICCR2_RS        0x04
  69 #define ICCR2_ST        0x02
  70
  71 #define ICMR1_CKS_MASK  0x70
  72 #define ICMR1_BCWP      0x08
  73 #define ICMR1_CKS(_x)   ((((_x) << 4) & ICMR1_CKS_MASK) | ICMR1_BCWP)
  74
  75 #define ICMR3_RDRFS     0x20
  76 #define ICMR3_ACKWP     0x10
  77 #define ICMR3_ACKBT     0x08
  78
  79 #define ICIER_TIE       0x80
  80 #define ICIER_TEIE      0x40
  81 #define ICIER_RIE       0x20
  82 #define ICIER_NAKIE     0x10
  83
  84 #define ICSR2_NACKF     0x10
  85
  86 /* ICBRx (@ PCLK 33MHz) */
  87 #define ICBR_RESERVED   0xe0 /* Should be 1 on writes */
  88 #define ICBRL_SP100K    (19 | ICBR_RESERVED)
  89 #define ICBRH_SP100K    (16 | ICBR_RESERVED)
  90 #define ICBRL_SP400K    (21 | ICBR_RESERVED)
  91 #define ICBRH_SP400K    (9 | ICBR_RESERVED)
  92
  93 #define RIIC_INIT_MSG   -1
  94
  95 struct riic_dev {
  96         void __iomem *base;
  97         u8 *buf;
  98         struct i2c_msg *msg;
  99         int bytes_left;
 100         int err;
 101         int is_last;
 102         struct completion msg_done;
 103         struct i2c_adapter adapter;
 104         struct clk *clk;
 105 };
 106
 107 struct riic_irq_desc {
 108         int res_num;
 109         irq_handler_t isr;
 110         char *name;
 111 };
 112
 113 static inline void riic_clear_set_bit(struct riic_dev *riic, u8 clear, u8 set, u8 reg)
 114 {
 115         writeb((readb(riic->base + reg) & ~clear) | set, riic->base + reg);
 116 }
 117
 118 static int riic_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 119 {
 120         struct riic_dev *riic = i2c_get_adapdata(adap);
 121         unsigned long time_left;
 122         int i, ret;
 123         u8 start_bit;
 124
 125         ret = clk_prepare_enable(riic->clk);
 126         if (ret)
 127                 return ret;
 128
 129         if (readb(riic->base + RIIC_ICCR2) & ICCR2_BBSY) {
 130                 riic->err = -EBUSY;
 131                 goto out;
 132         }
 133
 134         reinit_completion(&riic->msg_done);
 135         riic->err = 0;
 136
 137         writeb(0, riic->base + RIIC_ICSR2);
 138
 139         for (i = 0, start_bit = ICCR2_ST; i < num; i++) {
 140                 riic->bytes_left = RIIC_INIT_MSG;
 141                 riic->buf = msgs[i].buf;
 142                 riic->msg = &msgs[i];
 143                 riic->is_last = (i == num - 1);
 144
 145                 writeb(ICIER_NAKIE | ICIER_TIE, riic->base + RIIC_ICIER);
 146
 147                 writeb(start_bit, riic->base + RIIC_ICCR2);
 148
 149                 time_left = wait_for_completion_timeout(&riic->msg_done, riic->adapter.timeout);
 150                 if (time_left == 0)
 151                         riic->err = -ETIMEDOUT;
 152
 153                 if (riic->err)
 154                         break;
 155
 156                 start_bit = ICCR2_RS;
 157         }
 158
 159  out:
 160         clk_disable_unprepare(riic->clk);
 161
 162         return riic->err ?: num;
 163 }
 164
 165 static irqreturn_t riic_tdre_isr(int irq, void *data)
 166 {
 167         struct riic_dev *riic = data;
 168         u8 val;
 169
 170         if (!riic->bytes_left)
 171                 return IRQ_NONE;
 172
 173         if (riic->bytes_left == RIIC_INIT_MSG) {
 174                 val = !!(riic->msg->flags & I2C_M_RD);
 175                 if (val)
 176                         /* On read, switch over to receive interrupt */
 177                         riic_clear_set_bit(riic, ICIER_TIE, ICIER_RIE, RIIC_ICIER);
 178                 else
 179                         /* On write, initialize length */
 180                         riic->bytes_left = riic->msg->len;
 181
 182                 val |= (riic->msg->addr << 1);
 183         } else {
 184                 val = *riic->buf;
 185                 riic->buf++;
 186                 riic->bytes_left--;
 187         }
 188
 189         /*
 190          * Switch to transmission ended interrupt when done. Do check here
 191          * after bytes_left was initialized to support SMBUS_QUICK (new msg has
 192          * 0 length then)
 193          */
 194         if (riic->bytes_left == 0)
 195                 riic_clear_set_bit(riic, ICIER_TIE, ICIER_TEIE, RIIC_ICIER);
 196
 197         /*
 198          * This acks the TIE interrupt. We get another TIE immediately if our
 199          * value could be moved to the shadow shift register right away. So
 200          * this must be after updates to ICIER (where we want to disable TIE)!
 201          */
 202         writeb(val, riic->base + RIIC_ICDRT);
 203
 204         return IRQ_HANDLED;
 205 }
 206
 207 static irqreturn_t riic_tend_isr(int irq, void *data)
 208 {
 209         struct riic_dev *riic = data;
 210
 211         if (readb(riic->base + RIIC_ICSR2) & ICSR2_NACKF) {
 212                 /* We got a NACKIE */
 213                 readb(riic->base + RIIC_ICDRR); /* dummy read */
 214                 riic->err = -ENXIO;
 215         } else if (riic->bytes_left) {
 216                 return IRQ_NONE;
 217         }
 218
 219         if (riic->is_last || riic->err)
 220                 writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
 221
 222         writeb(0, riic->base + RIIC_ICIER);
 223         complete(&riic->msg_done);
 224
 225         return IRQ_HANDLED;
 226 }
 227
 228 static irqreturn_t riic_rdrf_isr(int irq, void *data)
 229 {
 230         struct riic_dev *riic = data;
 231
 232         if (!riic->bytes_left)
 233                 return IRQ_NONE;
 234
 235         if (riic->bytes_left == RIIC_INIT_MSG) {
 236                 riic->bytes_left = riic->msg->len;
 237                 readb(riic->base + RIIC_ICDRR); /* dummy read */
 238                 return IRQ_HANDLED;
 239         }
 240
 241         if (riic->bytes_left == 1) {
 242                 /* STOP must come before we set ACKBT! */
 243                 if (riic->is_last)
 244                         writeb(ICCR2_SP, riic->base + RIIC_ICCR2);
 245
 246                 riic_clear_set_bit(riic, 0, ICMR3_ACKBT, RIIC_ICMR3);
 247
 248                 writeb(0, riic->base + RIIC_ICIER);
 249                 complete(&riic->msg_done);
 250         } else {
 251                 riic_clear_set_bit(riic, ICMR3_ACKBT, 0, RIIC_ICMR3);
 252         }
 253
 254         /* Reading acks the RIE interrupt */
 255         *riic->buf = readb(riic->base + RIIC_ICDRR);
 256         riic->buf++;
 257         riic->bytes_left--;
 258
 259         return IRQ_HANDLED;
 260 }
 261
 262 static u32 riic_func(struct i2c_adapter *adap)
 263 {
 264         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 265 }
 266
 267 static const struct i2c_algorithm riic_algo = {
 268         .master_xfer    = riic_xfer,
 269         .functionality  = riic_func,
 270 };
 271
 272 static int riic_init_hw(struct riic_dev *riic, u32 spd)
 273 {
 274         int ret;
 275         unsigned long rate;
 276
 277         ret = clk_prepare_enable(riic->clk);
 278         if (ret)
 279                 return ret;
 280
 281         /*
 282          * TODO: Implement formula to calculate the timing values depending on
 283          * variable parent clock rate and arbitrary bus speed
 284          */
 285         rate = clk_get_rate(riic->clk);
 286         if (rate != 33325000) {
 287                 dev_err(&riic->adapter.dev,
 288                         "invalid parent clk (%lu). Must be 33325000Hz\n", rate);
 289                 clk_disable_unprepare(riic->clk);
 290                 return -EINVAL;
 291         }
 292
 293         /* Changing the order of accessing IICRST and ICE may break things! */
 294         writeb(ICCR1_IICRST | ICCR1_SOWP, riic->base + RIIC_ICCR1);
 295         riic_clear_set_bit(riic, 0, ICCR1_ICE, RIIC_ICCR1);
 296
 297         switch (spd) {
 298         case 100000:
 299                 writeb(ICMR1_CKS(3), riic->base + RIIC_ICMR1);
 300                 writeb(ICBRH_SP100K, riic->base + RIIC_ICBRH);
 301                 writeb(ICBRL_SP100K, riic->base + RIIC_ICBRL);
 302                 break;
 303         case 400000:
 304                 writeb(ICMR1_CKS(1), riic->base + RIIC_ICMR1);
 305                 writeb(ICBRH_SP400K, riic->base + RIIC_ICBRH);
 306                 writeb(ICBRL_SP400K, riic->base + RIIC_ICBRL);
 307                 break;
 308         default:
 309                 dev_err(&riic->adapter.dev,
 310                         "unsupported bus speed (%dHz). Use 100000 or 400000\n", spd);
 311                 clk_disable_unprepare(riic->clk);
 312                 return -EINVAL;
 313         }
 314
 315         writeb(0, riic->base + RIIC_ICSER);
 316         writeb(ICMR3_ACKWP | ICMR3_RDRFS, riic->base + RIIC_ICMR3);
 317
 318         riic_clear_set_bit(riic, ICCR1_IICRST, 0, RIIC_ICCR1);
 319
 320         clk_disable_unprepare(riic->clk);
 321
 322         return 0;
 323 }
 324
 325 static struct riic_irq_desc riic_irqs[] = {
 326         { .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
 327         { .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
 328         { .res_num = 2, .isr = riic_tdre_isr, .name = "riic-tdre" },
 329         { .res_num = 5, .isr = riic_tend_isr, .name = "riic-nack" },
 330 };
 331
 332 static int riic_i2c_probe(struct platform_device *pdev)
 333 {
 334         struct device_node *np = pdev->dev.of_node;
 335         struct riic_dev *riic;
 336         struct i2c_adapter *adap;
 337         struct resource *res;
 338         u32 bus_rate = 0;
 339         int i, ret;
 340
 341         riic = devm_kzalloc(&pdev->dev, sizeof(*riic), GFP_KERNEL);
 342         if (!riic)
 343                 return -ENOMEM;
 344
 345         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 346         riic->base = devm_ioremap_resource(&pdev->dev, res);
 347         if (IS_ERR(riic->base))
 348                 return PTR_ERR(riic->base);
 349
 350         riic->clk = devm_clk_get(&pdev->dev, NULL);
 351         if (IS_ERR(riic->clk)) {
 352                 dev_err(&pdev->dev, "missing controller clock");
 353                 return PTR_ERR(riic->clk);
 354         }
 355
 356         for (i = 0; i < ARRAY_SIZE(riic_irqs); i++) {
 357                 res = platform_get_resource(pdev, IORESOURCE_IRQ, riic_irqs[i].res_num);
 358                 if (!res)
 359                         return -ENODEV;
 360
 361                 ret = devm_request_irq(&pdev->dev, res->start, riic_irqs[i].isr,
 362                                         0, riic_irqs[i].name, riic);
 363                 if (ret) {
 364                         dev_err(&pdev->dev, "failed to request irq %s\n", riic_irqs[i].name);
 365                         return ret;
 366                 }
 367         }
 368
 369         adap = &riic->adapter;
 370         i2c_set_adapdata(adap, riic);
 371         strlcpy(adap->name, "Renesas RIIC adapter", sizeof(adap->name));
 372         adap->owner = THIS_MODULE;
 373         adap->algo = &riic_algo;
 374         adap->dev.parent = &pdev->dev;
 375         adap->dev.of_node = pdev->dev.of_node;
 376
 377         init_completion(&riic->msg_done);
 378
 379         of_property_read_u32(np, "clock-frequency", &bus_rate);
 380         ret = riic_init_hw(riic, bus_rate);
 381         if (ret)
 382                 return ret;
 383
 384
 385         ret = i2c_add_adapter(adap);
 386         if (ret)
 387                 return ret;
 388
 389         platform_set_drvdata(pdev, riic);
 390
 391         dev_info(&pdev->dev, "registered with %dHz bus speed\n", bus_rate);
 392         return 0;
 393 }
 394
 395 static int riic_i2c_remove(struct platform_device *pdev)
 396 {
 397         struct riic_dev *riic = platform_get_drvdata(pdev);
 398
 399         writeb(0, riic->base + RIIC_ICIER);
 400         i2c_del_adapter(&riic->adapter);
 401
 402         return 0;
 403 }
 404
 405 static const struct of_device_id riic_i2c_dt_ids[] = {
 406         { .compatible = "renesas,riic-rz" },
 407         { /* Sentinel */ },
 408 };
 409
 410 static struct platform_driver riic_i2c_driver = {
 411         .probe          = riic_i2c_probe,
 412         .remove         = riic_i2c_remove,
 413         .driver         = {
 414                 .name   = "i2c-riic",
 415                 .of_match_table = riic_i2c_dt_ids,
 416         },
 417 };
 418
 419 module_platform_driver(riic_i2c_driver);
 420
 421 MODULE_DESCRIPTION("Renesas RIIC adapter");
 422 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 423 MODULE_LICENSE("GPL v2");
 424 MODULE_DEVICE_TABLE(of, riic_i2c_dt_ids);