drivers/pwm/pwm-atmel.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Driver for Atmel Pulse Width Modulation Controller
   4  *
   5  * Copyright (C) 2013 Atmel Corporation
   6  *               Bo Shen <voice.shen@atmel.com>
   7  *
   8  * Links to reference manuals for the supported PWM chips can be found in
   9  * Documentation/arch/arm/microchip.rst.
  10  *
  11  * Limitations:
  12  * - Periods start with the inactive level.
  13  * - Hardware has to be stopped in general to update settings.
  14  *
  15  * Software bugs/possible improvements:
  16  * - When atmel_pwm_apply() is called with state->enabled=false a change in
  17  *   state->polarity isn't honored.
  18  * - Instead of sleeping to wait for a completed period, the interrupt
  19  *   functionality could be used.
  20  */
  21
  22 #include <linux/clk.h>
  23 #include <linux/delay.h>
  24 #include <linux/err.h>
  25 #include <linux/io.h>
  26 #include <linux/module.h>
  27 #include <linux/of.h>
  28 #include <linux/platform_device.h>
  29 #include <linux/pwm.h>
  30 #include <linux/slab.h>
  31
  32 /* The following is global registers for PWM controller */
  33 #define PWM_ENA                 0x04
  34 #define PWM_DIS                 0x08
  35 #define PWM_SR                  0x0C
  36 #define PWM_ISR                 0x1C
  37 /* Bit field in SR */
  38 #define PWM_SR_ALL_CH_MASK      0x0F
  39
  40 /* The following register is PWM channel related registers */
  41 #define PWM_CH_REG_OFFSET       0x200
  42 #define PWM_CH_REG_SIZE         0x20
  43
  44 #define PWM_CMR                 0x0
  45 /* Bit field in CMR */
  46 #define PWM_CMR_CPOL            (1 << 9)
  47 #define PWM_CMR_UPD_CDTY        (1 << 10)
  48 #define PWM_CMR_CPRE_MSK        0xF
  49
  50 /* The following registers for PWM v1 */
  51 #define PWMV1_CDTY              0x04
  52 #define PWMV1_CPRD              0x08
  53 #define PWMV1_CUPD              0x10
  54
  55 /* The following registers for PWM v2 */
  56 #define PWMV2_CDTY              0x04
  57 #define PWMV2_CDTYUPD           0x08
  58 #define PWMV2_CPRD              0x0C
  59 #define PWMV2_CPRDUPD           0x10
  60
  61 #define PWM_MAX_PRES            10
  62
  63 struct atmel_pwm_registers {
  64         u8 period;
  65         u8 period_upd;
  66         u8 duty;
  67         u8 duty_upd;
  68 };
  69
  70 struct atmel_pwm_config {
  71         u32 period_bits;
  72 };
  73
  74 struct atmel_pwm_data {
  75         struct atmel_pwm_registers regs;
  76         struct atmel_pwm_config cfg;
  77 };
  78
  79 struct atmel_pwm_chip {
  80         struct clk *clk;
  81         void __iomem *base;
  82         const struct atmel_pwm_data *data;
  83
  84         /*
  85          * The hardware supports a mechanism to update a channel's duty cycle at
  86          * the end of the currently running period. When such an update is
  87          * pending we delay disabling the PWM until the new configuration is
  88          * active because otherwise pmw_config(duty_cycle=0); pwm_disable();
  89          * might not result in an inactive output.
  90          * This bitmask tracks for which channels an update is pending in
  91          * hardware.
  92          */
  93         u32 update_pending;
  94
  95         /* Protects .update_pending */
  96         spinlock_t lock;
  97 };
  98
  99 static inline struct atmel_pwm_chip *to_atmel_pwm_chip(struct pwm_chip *chip)
 100 {
 101         return pwmchip_get_drvdata(chip);
 102 }
 103
 104 static inline u32 atmel_pwm_readl(struct atmel_pwm_chip *chip,
 105                                   unsigned long offset)
 106 {
 107         return readl_relaxed(chip->base + offset);
 108 }
 109
 110 static inline void atmel_pwm_writel(struct atmel_pwm_chip *chip,
 111                                     unsigned long offset, unsigned long val)
 112 {
 113         writel_relaxed(val, chip->base + offset);
 114 }
 115
 116 static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip,
 117                                      unsigned int ch, unsigned long offset)
 118 {
 119         unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
 120
 121         return atmel_pwm_readl(chip, base + offset);
 122 }
 123
 124 static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
 125                                        unsigned int ch, unsigned long offset,
 126                                        unsigned long val)
 127 {
 128         unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
 129
 130         atmel_pwm_writel(chip, base + offset, val);
 131 }
 132
 133 static void atmel_pwm_update_pending(struct atmel_pwm_chip *chip)
 134 {
 135         /*
 136          * Each channel that has its bit in ISR set started a new period since
 137          * ISR was cleared and so there is no more update pending.  Note that
 138          * reading ISR clears it, so this needs to handle all channels to not
 139          * loose information.
 140          */
 141         u32 isr = atmel_pwm_readl(chip, PWM_ISR);
 142
 143         chip->update_pending &= ~isr;
 144 }
 145
 146 static void atmel_pwm_set_pending(struct atmel_pwm_chip *chip, unsigned int ch)
 147 {
 148         spin_lock(&chip->lock);
 149
 150         /*
 151          * Clear pending flags in hardware because otherwise there might still
 152          * be a stale flag in ISR.
 153          */
 154         atmel_pwm_update_pending(chip);
 155
 156         chip->update_pending |= (1 << ch);
 157
 158         spin_unlock(&chip->lock);
 159 }
 160
 161 static int atmel_pwm_test_pending(struct atmel_pwm_chip *chip, unsigned int ch)
 162 {
 163         int ret = 0;
 164
 165         spin_lock(&chip->lock);
 166
 167         if (chip->update_pending & (1 << ch)) {
 168                 atmel_pwm_update_pending(chip);
 169
 170                 if (chip->update_pending & (1 << ch))
 171                         ret = 1;
 172         }
 173
 174         spin_unlock(&chip->lock);
 175
 176         return ret;
 177 }
 178
 179 static int atmel_pwm_wait_nonpending(struct atmel_pwm_chip *chip, unsigned int ch)
 180 {
 181         unsigned long timeout = jiffies + 2 * HZ;
 182         int ret;
 183
 184         while ((ret = atmel_pwm_test_pending(chip, ch)) &&
 185                time_before(jiffies, timeout))
 186                 usleep_range(10, 100);
 187
 188         return ret ? -ETIMEDOUT : 0;
 189 }
 190
 191 static int atmel_pwm_calculate_cprd_and_pres(struct pwm_chip *chip,
 192                                              unsigned long clkrate,
 193                                              const struct pwm_state *state,
 194                                              unsigned long *cprd, u32 *pres)
 195 {
 196         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 197         unsigned long long cycles = state->period;
 198         int shift;
 199
 200         /* Calculate the period cycles and prescale value */
 201         cycles *= clkrate;
 202         do_div(cycles, NSEC_PER_SEC);
 203
 204         /*
 205          * The register for the period length is cfg.period_bits bits wide.
 206          * So for each bit the number of clock cycles is wider divide the input
 207          * clock frequency by two using pres and shift cprd accordingly.
 208          */
 209         shift = fls(cycles) - atmel_pwm->data->cfg.period_bits;
 210
 211         if (shift > PWM_MAX_PRES) {
 212                 dev_err(pwmchip_parent(chip), "pres exceeds the maximum value\n");
 213                 return -EINVAL;
 214         } else if (shift > 0) {
 215                 *pres = shift;
 216                 cycles >>= *pres;
 217         } else {
 218                 *pres = 0;
 219         }
 220
 221         *cprd = cycles;
 222
 223         return 0;
 224 }
 225
 226 static void atmel_pwm_calculate_cdty(const struct pwm_state *state,
 227                                      unsigned long clkrate, unsigned long cprd,
 228                                      u32 pres, unsigned long *cdty)
 229 {
 230         unsigned long long cycles = state->duty_cycle;
 231
 232         cycles *= clkrate;
 233         do_div(cycles, NSEC_PER_SEC);
 234         cycles >>= pres;
 235         *cdty = cprd - cycles;
 236 }
 237
 238 static void atmel_pwm_update_cdty(struct pwm_chip *chip, struct pwm_device *pwm,
 239                                   unsigned long cdty)
 240 {
 241         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 242         u32 val;
 243
 244         if (atmel_pwm->data->regs.duty_upd ==
 245             atmel_pwm->data->regs.period_upd) {
 246                 val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
 247                 val &= ~PWM_CMR_UPD_CDTY;
 248                 atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
 249         }
 250
 251         atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
 252                             atmel_pwm->data->regs.duty_upd, cdty);
 253         atmel_pwm_set_pending(atmel_pwm, pwm->hwpwm);
 254 }
 255
 256 static void atmel_pwm_set_cprd_cdty(struct pwm_chip *chip,
 257                                     struct pwm_device *pwm,
 258                                     unsigned long cprd, unsigned long cdty)
 259 {
 260         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 261
 262         atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
 263                             atmel_pwm->data->regs.duty, cdty);
 264         atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
 265                             atmel_pwm->data->regs.period, cprd);
 266 }
 267
 268 static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
 269                               bool disable_clk)
 270 {
 271         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 272         unsigned long timeout;
 273
 274         atmel_pwm_wait_nonpending(atmel_pwm, pwm->hwpwm);
 275
 276         atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
 277
 278         /*
 279          * Wait for the PWM channel disable operation to be effective before
 280          * stopping the clock.
 281          */
 282         timeout = jiffies + 2 * HZ;
 283
 284         while ((atmel_pwm_readl(atmel_pwm, PWM_SR) & (1 << pwm->hwpwm)) &&
 285                time_before(jiffies, timeout))
 286                 usleep_range(10, 100);
 287
 288         if (disable_clk)
 289                 clk_disable(atmel_pwm->clk);
 290 }
 291
 292 static int atmel_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 293                            const struct pwm_state *state)
 294 {
 295         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 296         unsigned long cprd, cdty;
 297         u32 pres, val;
 298         int ret;
 299
 300         if (state->enabled) {
 301                 unsigned long clkrate = clk_get_rate(atmel_pwm->clk);
 302
 303                 if (pwm->state.enabled &&
 304                     pwm->state.polarity == state->polarity &&
 305                     pwm->state.period == state->period) {
 306                         u32 cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
 307
 308                         cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
 309                                                   atmel_pwm->data->regs.period);
 310                         pres = cmr & PWM_CMR_CPRE_MSK;
 311
 312                         atmel_pwm_calculate_cdty(state, clkrate, cprd, pres, &cdty);
 313                         atmel_pwm_update_cdty(chip, pwm, cdty);
 314                         return 0;
 315                 }
 316
 317                 ret = atmel_pwm_calculate_cprd_and_pres(chip, clkrate, state, &cprd,
 318                                                         &pres);
 319                 if (ret) {
 320                         dev_err(pwmchip_parent(chip),
 321                                 "failed to calculate cprd and prescaler\n");
 322                         return ret;
 323                 }
 324
 325                 atmel_pwm_calculate_cdty(state, clkrate, cprd, pres, &cdty);
 326
 327                 if (pwm->state.enabled) {
 328                         atmel_pwm_disable(chip, pwm, false);
 329                 } else {
 330                         ret = clk_enable(atmel_pwm->clk);
 331                         if (ret) {
 332                                 dev_err(pwmchip_parent(chip), "failed to enable clock\n");
 333                                 return ret;
 334                         }
 335                 }
 336
 337                 /* It is necessary to preserve CPOL, inside CMR */
 338                 val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
 339                 val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
 340                 if (state->polarity == PWM_POLARITY_NORMAL)
 341                         val &= ~PWM_CMR_CPOL;
 342                 else
 343                         val |= PWM_CMR_CPOL;
 344                 atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
 345                 atmel_pwm_set_cprd_cdty(chip, pwm, cprd, cdty);
 346                 atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
 347         } else if (pwm->state.enabled) {
 348                 atmel_pwm_disable(chip, pwm, true);
 349         }
 350
 351         return 0;
 352 }
 353
 354 static int atmel_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 355                                struct pwm_state *state)
 356 {
 357         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 358         u32 sr, cmr;
 359
 360         sr = atmel_pwm_readl(atmel_pwm, PWM_SR);
 361         cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
 362
 363         if (sr & (1 << pwm->hwpwm)) {
 364                 unsigned long rate = clk_get_rate(atmel_pwm->clk);
 365                 u32 cdty, cprd, pres;
 366                 u64 tmp;
 367
 368                 pres = cmr & PWM_CMR_CPRE_MSK;
 369
 370                 cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
 371                                           atmel_pwm->data->regs.period);
 372                 tmp = (u64)cprd * NSEC_PER_SEC;
 373                 tmp <<= pres;
 374                 state->period = DIV64_U64_ROUND_UP(tmp, rate);
 375
 376                 /* Wait for an updated duty_cycle queued in hardware */
 377                 atmel_pwm_wait_nonpending(atmel_pwm, pwm->hwpwm);
 378
 379                 cdty = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
 380                                           atmel_pwm->data->regs.duty);
 381                 tmp = (u64)(cprd - cdty) * NSEC_PER_SEC;
 382                 tmp <<= pres;
 383                 state->duty_cycle = DIV64_U64_ROUND_UP(tmp, rate);
 384
 385                 state->enabled = true;
 386         } else {
 387                 state->enabled = false;
 388         }
 389
 390         if (cmr & PWM_CMR_CPOL)
 391                 state->polarity = PWM_POLARITY_INVERSED;
 392         else
 393                 state->polarity = PWM_POLARITY_NORMAL;
 394
 395         return 0;
 396 }
 397
 398 static const struct pwm_ops atmel_pwm_ops = {
 399         .apply = atmel_pwm_apply,
 400         .get_state = atmel_pwm_get_state,
 401 };
 402
 403 static const struct atmel_pwm_data atmel_sam9rl_pwm_data = {
 404         .regs = {
 405                 .period         = PWMV1_CPRD,
 406                 .period_upd     = PWMV1_CUPD,
 407                 .duty           = PWMV1_CDTY,
 408                 .duty_upd       = PWMV1_CUPD,
 409         },
 410         .cfg = {
 411                 /* 16 bits to keep period and duty. */
 412                 .period_bits    = 16,
 413         },
 414 };
 415
 416 static const struct atmel_pwm_data atmel_sama5_pwm_data = {
 417         .regs = {
 418                 .period         = PWMV2_CPRD,
 419                 .period_upd     = PWMV2_CPRDUPD,
 420                 .duty           = PWMV2_CDTY,
 421                 .duty_upd       = PWMV2_CDTYUPD,
 422         },
 423         .cfg = {
 424                 /* 16 bits to keep period and duty. */
 425                 .period_bits    = 16,
 426         },
 427 };
 428
 429 static const struct atmel_pwm_data mchp_sam9x60_pwm_data = {
 430         .regs = {
 431                 .period         = PWMV1_CPRD,
 432                 .period_upd     = PWMV1_CUPD,
 433                 .duty           = PWMV1_CDTY,
 434                 .duty_upd       = PWMV1_CUPD,
 435         },
 436         .cfg = {
 437                 /* 32 bits to keep period and duty. */
 438                 .period_bits    = 32,
 439         },
 440 };
 441
 442 static const struct of_device_id atmel_pwm_dt_ids[] = {
 443         {
 444                 .compatible = "atmel,at91sam9rl-pwm",
 445                 .data = &atmel_sam9rl_pwm_data,
 446         }, {
 447                 .compatible = "atmel,sama5d3-pwm",
 448                 .data = &atmel_sama5_pwm_data,
 449         }, {
 450                 .compatible = "atmel,sama5d2-pwm",
 451                 .data = &atmel_sama5_pwm_data,
 452         }, {
 453                 .compatible = "microchip,sam9x60-pwm",
 454                 .data = &mchp_sam9x60_pwm_data,
 455         }, {
 456                 /* sentinel */
 457         },
 458 };
 459 MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
 460
 461 static int atmel_pwm_enable_clk_if_on(struct pwm_chip *chip, bool on)
 462 {
 463         struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 464         unsigned int i, cnt = 0;
 465         unsigned long sr;
 466         int ret = 0;
 467
 468         sr = atmel_pwm_readl(atmel_pwm, PWM_SR) & PWM_SR_ALL_CH_MASK;
 469         if (!sr)
 470                 return 0;
 471
 472         cnt = bitmap_weight(&sr, chip->npwm);
 473
 474         if (!on)
 475                 goto disable_clk;
 476
 477         for (i = 0; i < cnt; i++) {
 478                 ret = clk_enable(atmel_pwm->clk);
 479                 if (ret) {
 480                         dev_err(pwmchip_parent(chip),
 481                                 "failed to enable clock for pwm %pe\n",
 482                                 ERR_PTR(ret));
 483
 484                         cnt = i;
 485                         goto disable_clk;
 486                 }
 487         }
 488
 489         return 0;
 490
 491 disable_clk:
 492         while (cnt--)
 493                 clk_disable(atmel_pwm->clk);
 494
 495         return ret;
 496 }
 497
 498 static int atmel_pwm_probe(struct platform_device *pdev)
 499 {
 500         struct atmel_pwm_chip *atmel_pwm;
 501         struct pwm_chip *chip;
 502         int ret;
 503
 504         chip = devm_pwmchip_alloc(&pdev->dev, 4, sizeof(*atmel_pwm));
 505         if (IS_ERR(chip))
 506                 return PTR_ERR(chip);
 507
 508         atmel_pwm = to_atmel_pwm_chip(chip);
 509         atmel_pwm->data = of_device_get_match_data(&pdev->dev);
 510
 511         atmel_pwm->update_pending = 0;
 512         spin_lock_init(&atmel_pwm->lock);
 513
 514         atmel_pwm->base = devm_platform_ioremap_resource(pdev, 0);
 515         if (IS_ERR(atmel_pwm->base))
 516                 return PTR_ERR(atmel_pwm->base);
 517
 518         atmel_pwm->clk = devm_clk_get_prepared(&pdev->dev, NULL);
 519         if (IS_ERR(atmel_pwm->clk))
 520                 return dev_err_probe(&pdev->dev, PTR_ERR(atmel_pwm->clk),
 521                                      "failed to get prepared PWM clock\n");
 522
 523         chip->ops = &atmel_pwm_ops;
 524
 525         ret = atmel_pwm_enable_clk_if_on(chip, true);
 526         if (ret < 0)
 527                 return ret;
 528
 529         ret = devm_pwmchip_add(&pdev->dev, chip);
 530         if (ret < 0) {
 531                 dev_err_probe(&pdev->dev, ret, "failed to add PWM chip\n");
 532                 goto disable_clk;
 533         }
 534
 535         return 0;
 536
 537 disable_clk:
 538         atmel_pwm_enable_clk_if_on(chip, false);
 539
 540         return ret;
 541 }
 542
 543 static struct platform_driver atmel_pwm_driver = {
 544         .driver = {
 545                 .name = "atmel-pwm",
 546                 .of_match_table = atmel_pwm_dt_ids,
 547         },
 548         .probe = atmel_pwm_probe,
 549 };
 550 module_platform_driver(atmel_pwm_driver);
 551
 552 MODULE_ALIAS("platform:atmel-pwm");
 553 MODULE_AUTHOR("Bo Shen <voice.shen@atmel.com>");
 554 MODULE_DESCRIPTION("Atmel PWM driver");
 555 MODULE_LICENSE("GPL v2");