drivers/rtc/rtc-meson.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * RTC driver for the interal RTC block in the Amlogic Meson6, Meson8,
   4  * Meson8b and Meson8m2 SoCs.
   5  *
   6  * The RTC is split in to two parts, the AHB front end and a simple serial
   7  * connection to the actual registers. This driver manages both parts.
   8  *
   9  * Copyright (c) 2018 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
  10  * Copyright (c) 2015 Ben Dooks <ben.dooks@codethink.co.uk> for Codethink Ltd
  11  * Based on origin by Carlo Caione <carlo@endlessm.com>
  12  */
  13
  14 #include <linux/bitfield.h>
  15 #include <linux/delay.h>
  16 #include <linux/io.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/nvmem-provider.h>
  20 #include <linux/of.h>
  21 #include <linux/platform_device.h>
  22 #include <linux/regmap.h>
  23 #include <linux/regulator/consumer.h>
  24 #include <linux/reset.h>
  25 #include <linux/rtc.h>
  26
  27 /* registers accessed from cpu bus */
  28 #define RTC_ADDR0                               0x00
  29         #define RTC_ADDR0_LINE_SCLK             BIT(0)
  30         #define RTC_ADDR0_LINE_SEN              BIT(1)
  31         #define RTC_ADDR0_LINE_SDI              BIT(2)
  32         #define RTC_ADDR0_START_SER             BIT(17)
  33         #define RTC_ADDR0_WAIT_SER              BIT(22)
  34         #define RTC_ADDR0_DATA                  GENMASK(31, 24)
  35
  36 #define RTC_ADDR1                               0x04
  37         #define RTC_ADDR1_SDO                   BIT(0)
  38         #define RTC_ADDR1_S_READY               BIT(1)
  39
  40 #define RTC_ADDR2                               0x08
  41 #define RTC_ADDR3                               0x0c
  42
  43 #define RTC_REG4                                0x10
  44         #define RTC_REG4_STATIC_VALUE           GENMASK(7, 0)
  45
  46 /* rtc registers accessed via rtc-serial interface */
  47 #define RTC_COUNTER             (0)
  48 #define RTC_SEC_ADJ             (2)
  49 #define RTC_REGMEM_0            (4)
  50 #define RTC_REGMEM_1            (5)
  51 #define RTC_REGMEM_2            (6)
  52 #define RTC_REGMEM_3            (7)
  53
  54 #define RTC_ADDR_BITS           (3)     /* number of address bits to send */
  55 #define RTC_DATA_BITS           (32)    /* number of data bits to tx/rx */
  56
  57 #define MESON_STATIC_BIAS_CUR   (0x5 << 1)
  58 #define MESON_STATIC_VOLTAGE    (0x3 << 11)
  59 #define MESON_STATIC_DEFAULT    (MESON_STATIC_BIAS_CUR | MESON_STATIC_VOLTAGE)
  60
  61 struct meson_rtc {
  62         struct rtc_device       *rtc;           /* rtc device we created */
  63         struct device           *dev;           /* device we bound from */
  64         struct reset_control    *reset;         /* reset source */
  65         struct regulator        *vdd;           /* voltage input */
  66         struct regmap           *peripheral;    /* peripheral registers */
  67         struct regmap           *serial;        /* serial registers */
  68 };
  69
  70 static const struct regmap_config meson_rtc_peripheral_regmap_config = {
  71         .name           = "peripheral-registers",
  72         .reg_bits       = 8,
  73         .val_bits       = 32,
  74         .reg_stride     = 4,
  75         .max_register   = RTC_REG4,
  76         .fast_io        = true,
  77 };
  78
  79 /* RTC front-end serialiser controls */
  80
  81 static void meson_rtc_sclk_pulse(struct meson_rtc *rtc)
  82 {
  83         udelay(5);
  84         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK, 0);
  85         udelay(5);
  86         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SCLK,
  87                            RTC_ADDR0_LINE_SCLK);
  88 }
  89
  90 static void meson_rtc_send_bit(struct meson_rtc *rtc, unsigned int bit)
  91 {
  92         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI,
  93                            bit ? RTC_ADDR0_LINE_SDI : 0);
  94         meson_rtc_sclk_pulse(rtc);
  95 }
  96
  97 static void meson_rtc_send_bits(struct meson_rtc *rtc, u32 data,
  98                                 unsigned int nr)
  99 {
 100         u32 bit = 1 << (nr - 1);
 101
 102         while (bit) {
 103                 meson_rtc_send_bit(rtc, data & bit);
 104                 bit >>= 1;
 105         }
 106 }
 107
 108 static void meson_rtc_set_dir(struct meson_rtc *rtc, u32 mode)
 109 {
 110         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN, 0);
 111         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
 112         meson_rtc_send_bit(rtc, mode);
 113         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SDI, 0);
 114 }
 115
 116 static u32 meson_rtc_get_data(struct meson_rtc *rtc)
 117 {
 118         u32 tmp, val = 0;
 119         int bit;
 120
 121         for (bit = 0; bit < RTC_DATA_BITS; bit++) {
 122                 meson_rtc_sclk_pulse(rtc);
 123                 val <<= 1;
 124
 125                 regmap_read(rtc->peripheral, RTC_ADDR1, &tmp);
 126                 val |= tmp & RTC_ADDR1_SDO;
 127         }
 128
 129         return val;
 130 }
 131
 132 static int meson_rtc_get_bus(struct meson_rtc *rtc)
 133 {
 134         int ret, retries;
 135         u32 val;
 136
 137         /* prepare bus for transfers, set all lines low */
 138         val = RTC_ADDR0_LINE_SDI | RTC_ADDR0_LINE_SEN | RTC_ADDR0_LINE_SCLK;
 139         regmap_update_bits(rtc->peripheral, RTC_ADDR0, val, 0);
 140
 141         for (retries = 0; retries < 3; retries++) {
 142                 /* wait for the bus to be ready */
 143                 if (!regmap_read_poll_timeout(rtc->peripheral, RTC_ADDR1, val,
 144                                               val & RTC_ADDR1_S_READY, 10,
 145                                               10000))
 146                         return 0;
 147
 148                 dev_warn(rtc->dev, "failed to get bus, resetting RTC\n");
 149
 150                 ret = reset_control_reset(rtc->reset);
 151                 if (ret)
 152                         return ret;
 153         }
 154
 155         dev_err(rtc->dev, "bus is not ready\n");
 156         return -ETIMEDOUT;
 157 }
 158
 159 static int meson_rtc_serial_bus_reg_read(void *context, unsigned int reg,
 160                                          unsigned int *data)
 161 {
 162         struct meson_rtc *rtc = context;
 163         int ret;
 164
 165         ret = meson_rtc_get_bus(rtc);
 166         if (ret)
 167                 return ret;
 168
 169         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
 170                            RTC_ADDR0_LINE_SEN);
 171         meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
 172         meson_rtc_set_dir(rtc, 0);
 173         *data = meson_rtc_get_data(rtc);
 174
 175         return 0;
 176 }
 177
 178 static int meson_rtc_serial_bus_reg_write(void *context, unsigned int reg,
 179                                           unsigned int data)
 180 {
 181         struct meson_rtc *rtc = context;
 182         int ret;
 183
 184         ret = meson_rtc_get_bus(rtc);
 185         if (ret)
 186                 return ret;
 187
 188         regmap_update_bits(rtc->peripheral, RTC_ADDR0, RTC_ADDR0_LINE_SEN,
 189                            RTC_ADDR0_LINE_SEN);
 190         meson_rtc_send_bits(rtc, data, RTC_DATA_BITS);
 191         meson_rtc_send_bits(rtc, reg, RTC_ADDR_BITS);
 192         meson_rtc_set_dir(rtc, 1);
 193
 194         return 0;
 195 }
 196
 197 static const struct regmap_bus meson_rtc_serial_bus = {
 198         .reg_read       = meson_rtc_serial_bus_reg_read,
 199         .reg_write      = meson_rtc_serial_bus_reg_write,
 200 };
 201
 202 static const struct regmap_config meson_rtc_serial_regmap_config = {
 203         .name           = "serial-registers",
 204         .reg_bits       = 4,
 205         .reg_stride     = 1,
 206         .val_bits       = 32,
 207         .max_register   = RTC_REGMEM_3,
 208         .fast_io        = false,
 209 };
 210
 211 static int meson_rtc_write_static(struct meson_rtc *rtc, u32 data)
 212 {
 213         u32 tmp;
 214
 215         regmap_write(rtc->peripheral, RTC_REG4,
 216                      FIELD_PREP(RTC_REG4_STATIC_VALUE, (data >> 8)));
 217
 218         /* write the static value and start the auto serializer */
 219         tmp = FIELD_PREP(RTC_ADDR0_DATA, (data & 0xff)) | RTC_ADDR0_START_SER;
 220         regmap_update_bits(rtc->peripheral, RTC_ADDR0,
 221                            RTC_ADDR0_DATA | RTC_ADDR0_START_SER, tmp);
 222
 223         /* wait for the auto serializer to complete */
 224         return regmap_read_poll_timeout(rtc->peripheral, RTC_REG4, tmp,
 225                                         !(tmp & RTC_ADDR0_WAIT_SER), 10,
 226                                         10000);
 227 }
 228
 229 /* RTC interface layer functions */
 230
 231 static int meson_rtc_gettime(struct device *dev, struct rtc_time *tm)
 232 {
 233         struct meson_rtc *rtc = dev_get_drvdata(dev);
 234         u32 time;
 235         int ret;
 236
 237         ret = regmap_read(rtc->serial, RTC_COUNTER, &time);
 238         if (!ret)
 239                 rtc_time64_to_tm(time, tm);
 240
 241         return ret;
 242 }
 243
 244 static int meson_rtc_settime(struct device *dev, struct rtc_time *tm)
 245 {
 246         struct meson_rtc *rtc = dev_get_drvdata(dev);
 247
 248         return regmap_write(rtc->serial, RTC_COUNTER, rtc_tm_to_time64(tm));
 249 }
 250
 251 static const struct rtc_class_ops meson_rtc_ops = {
 252         .read_time      = meson_rtc_gettime,
 253         .set_time       = meson_rtc_settime,
 254 };
 255
 256 /* NVMEM interface layer functions */
 257
 258 static int meson_rtc_regmem_read(void *context, unsigned int offset,
 259                                  void *buf, size_t bytes)
 260 {
 261         struct meson_rtc *rtc = context;
 262         unsigned int read_offset, read_size;
 263
 264         read_offset = RTC_REGMEM_0 + (offset / 4);
 265         read_size = bytes / 4;
 266
 267         return regmap_bulk_read(rtc->serial, read_offset, buf, read_size);
 268 }
 269
 270 static int meson_rtc_regmem_write(void *context, unsigned int offset,
 271                                   void *buf, size_t bytes)
 272 {
 273         struct meson_rtc *rtc = context;
 274         unsigned int write_offset, write_size;
 275
 276         write_offset = RTC_REGMEM_0 + (offset / 4);
 277         write_size = bytes / 4;
 278
 279         return regmap_bulk_write(rtc->serial, write_offset, buf, write_size);
 280 }
 281
 282 static int meson_rtc_probe(struct platform_device *pdev)
 283 {
 284         struct nvmem_config meson_rtc_nvmem_config = {
 285                 .name = "meson-rtc-regmem",
 286                 .type = NVMEM_TYPE_BATTERY_BACKED,
 287                 .word_size = 4,
 288                 .stride = 4,
 289                 .size = 4 * 4,
 290                 .reg_read = meson_rtc_regmem_read,
 291                 .reg_write = meson_rtc_regmem_write,
 292         };
 293         struct device *dev = &pdev->dev;
 294         struct meson_rtc *rtc;
 295         void __iomem *base;
 296         int ret;
 297         u32 tm;
 298
 299         rtc = devm_kzalloc(dev, sizeof(struct meson_rtc), GFP_KERNEL);
 300         if (!rtc)
 301                 return -ENOMEM;
 302
 303         rtc->rtc = devm_rtc_allocate_device(dev);
 304         if (IS_ERR(rtc->rtc))
 305                 return PTR_ERR(rtc->rtc);
 306
 307         platform_set_drvdata(pdev, rtc);
 308
 309         rtc->dev = dev;
 310
 311         rtc->rtc->ops = &meson_rtc_ops;
 312         rtc->rtc->range_max = U32_MAX;
 313
 314         base = devm_platform_ioremap_resource(pdev, 0);
 315         if (IS_ERR(base))
 316                 return PTR_ERR(base);
 317
 318         rtc->peripheral = devm_regmap_init_mmio(dev, base,
 319                                         &meson_rtc_peripheral_regmap_config);
 320         if (IS_ERR(rtc->peripheral)) {
 321                 dev_err(dev, "failed to create peripheral regmap\n");
 322                 return PTR_ERR(rtc->peripheral);
 323         }
 324
 325         rtc->reset = devm_reset_control_get(dev, NULL);
 326         if (IS_ERR(rtc->reset)) {
 327                 dev_err(dev, "missing reset line\n");
 328                 return PTR_ERR(rtc->reset);
 329         }
 330
 331         rtc->vdd = devm_regulator_get(dev, "vdd");
 332         if (IS_ERR(rtc->vdd)) {
 333                 dev_err(dev, "failed to get the vdd-supply\n");
 334                 return PTR_ERR(rtc->vdd);
 335         }
 336
 337         ret = regulator_enable(rtc->vdd);
 338         if (ret) {
 339                 dev_err(dev, "failed to enable vdd-supply\n");
 340                 return ret;
 341         }
 342
 343         ret = meson_rtc_write_static(rtc, MESON_STATIC_DEFAULT);
 344         if (ret) {
 345                 dev_err(dev, "failed to set static values\n");
 346                 goto out_disable_vdd;
 347         }
 348
 349         rtc->serial = devm_regmap_init(dev, &meson_rtc_serial_bus, rtc,
 350                                        &meson_rtc_serial_regmap_config);
 351         if (IS_ERR(rtc->serial)) {
 352                 dev_err(dev, "failed to create serial regmap\n");
 353                 ret = PTR_ERR(rtc->serial);
 354                 goto out_disable_vdd;
 355         }
 356
 357         /*
 358          * check if we can read RTC counter, if not then the RTC is probably
 359          * not functional. If it isn't probably best to not bind.
 360          */
 361         ret = regmap_read(rtc->serial, RTC_COUNTER, &tm);
 362         if (ret) {
 363                 dev_err(dev, "cannot read RTC counter, RTC not functional\n");
 364                 goto out_disable_vdd;
 365         }
 366
 367         meson_rtc_nvmem_config.priv = rtc;
 368         ret = devm_rtc_nvmem_register(rtc->rtc, &meson_rtc_nvmem_config);
 369         if (ret)
 370                 goto out_disable_vdd;
 371
 372         ret = devm_rtc_register_device(rtc->rtc);
 373         if (ret)
 374                 goto out_disable_vdd;
 375
 376         return 0;
 377
 378 out_disable_vdd:
 379         regulator_disable(rtc->vdd);
 380         return ret;
 381 }
 382
 383 static const __maybe_unused struct of_device_id meson_rtc_dt_match[] = {
 384         { .compatible = "amlogic,meson6-rtc", },
 385         { .compatible = "amlogic,meson8-rtc", },
 386         { .compatible = "amlogic,meson8b-rtc", },
 387         { .compatible = "amlogic,meson8m2-rtc", },
 388         { },
 389 };
 390 MODULE_DEVICE_TABLE(of, meson_rtc_dt_match);
 391
 392 static struct platform_driver meson_rtc_driver = {
 393         .probe          = meson_rtc_probe,
 394         .driver         = {
 395                 .name           = "meson-rtc",
 396                 .of_match_table = of_match_ptr(meson_rtc_dt_match),
 397         },
 398 };
 399 module_platform_driver(meson_rtc_driver);
 400
 401 MODULE_DESCRIPTION("Amlogic Meson RTC Driver");
 402 MODULE_AUTHOR("Ben Dooks <ben.dooks@codethink.co.uk>");
 403 MODULE_AUTHOR("Martin Blumenstingl <martin.blumenstingl@googlemail.com>");
 404 MODULE_LICENSE("GPL v2");
 405 MODULE_ALIAS("platform:meson-rtc");