drivers/pwm/pwm-sifive.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2017-2018 SiFive
   4  * For SiFive's PWM IP block documentation please refer Chapter 14 of
   5  * Reference Manual : https://static.dev.sifive.com/FU540-C000-v1.0.pdf
   6  *
   7  * Limitations:
   8  * - When changing both duty cycle and period, we cannot prevent in
   9  *   software that the output might produce a period with mixed
  10  *   settings (new period length and old duty cycle).
  11  * - The hardware cannot generate a 100% duty cycle.
  12  * - The hardware generates only inverted output.
  13  */
  14 #include <linux/clk.h>
  15 #include <linux/io.h>
  16 #include <linux/module.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/pwm.h>
  19 #include <linux/slab.h>
  20 #include <linux/bitfield.h>
  21
  22 /* Register offsets */
  23 #define PWM_SIFIVE_PWMCFG               0x0
  24 #define PWM_SIFIVE_PWMCOUNT             0x8
  25 #define PWM_SIFIVE_PWMS                 0x10
  26 #define PWM_SIFIVE_PWMCMP0              0x20
  27
  28 /* PWMCFG fields */
  29 #define PWM_SIFIVE_PWMCFG_SCALE         GENMASK(3, 0)
  30 #define PWM_SIFIVE_PWMCFG_STICKY        BIT(8)
  31 #define PWM_SIFIVE_PWMCFG_ZERO_CMP      BIT(9)
  32 #define PWM_SIFIVE_PWMCFG_DEGLITCH      BIT(10)
  33 #define PWM_SIFIVE_PWMCFG_EN_ALWAYS     BIT(12)
  34 #define PWM_SIFIVE_PWMCFG_EN_ONCE       BIT(13)
  35 #define PWM_SIFIVE_PWMCFG_CENTER        BIT(16)
  36 #define PWM_SIFIVE_PWMCFG_GANG          BIT(24)
  37 #define PWM_SIFIVE_PWMCFG_IP            BIT(28)
  38
  39 /* PWM_SIFIVE_SIZE_PWMCMP is used to calculate offset for pwmcmpX registers */
  40 #define PWM_SIFIVE_SIZE_PWMCMP          4
  41 #define PWM_SIFIVE_CMPWIDTH             16
  42 #define PWM_SIFIVE_DEFAULT_PERIOD       10000000
  43
  44 struct pwm_sifive_ddata {
  45         struct pwm_chip chip;
  46         struct mutex lock; /* lock to protect user_count */
  47         struct notifier_block notifier;
  48         struct clk *clk;
  49         void __iomem *regs;
  50         unsigned int real_period;
  51         unsigned int approx_period;
  52         int user_count;
  53 };
  54
  55 static inline
  56 struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *c)
  57 {
  58         return container_of(c, struct pwm_sifive_ddata, chip);
  59 }
  60
  61 static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm)
  62 {
  63         struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
  64
  65         mutex_lock(&ddata->lock);
  66         ddata->user_count++;
  67         mutex_unlock(&ddata->lock);
  68
  69         return 0;
  70 }
  71
  72 static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
  73 {
  74         struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
  75
  76         mutex_lock(&ddata->lock);
  77         ddata->user_count--;
  78         mutex_unlock(&ddata->lock);
  79 }
  80
  81 static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
  82                                     unsigned long rate)
  83 {
  84         unsigned long long num;
  85         unsigned long scale_pow;
  86         int scale;
  87         u32 val;
  88         /*
  89          * The PWM unit is used with pwmzerocmp=0, so the only way to modify the
  90          * period length is using pwmscale which provides the number of bits the
  91          * counter is shifted before being feed to the comparators. A period
  92          * lasts (1 << (PWM_SIFIVE_CMPWIDTH + pwmscale)) clock ticks.
  93          * (1 << (PWM_SIFIVE_CMPWIDTH + scale)) * 10^9/rate = period
  94          */
  95         scale_pow = div64_ul(ddata->approx_period * (u64)rate, NSEC_PER_SEC);
  96         scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf);
  97
  98         val = PWM_SIFIVE_PWMCFG_EN_ALWAYS |
  99               FIELD_PREP(PWM_SIFIVE_PWMCFG_SCALE, scale);
 100         writel(val, ddata->regs + PWM_SIFIVE_PWMCFG);
 101
 102         /* As scale <= 15 the shift operation cannot overflow. */
 103         num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
 104         ddata->real_period = div64_ul(num, rate);
 105         dev_dbg(ddata->chip.dev,
 106                 "New real_period = %u ns\n", ddata->real_period);
 107 }
 108
 109 static void pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 110                                  struct pwm_state *state)
 111 {
 112         struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
 113         u32 duty, val;
 114
 115         duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP0 +
 116                      pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
 117
 118         state->enabled = duty > 0;
 119
 120         val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
 121         if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS))
 122                 state->enabled = false;
 123
 124         state->period = ddata->real_period;
 125         state->duty_cycle =
 126                 (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
 127         state->polarity = PWM_POLARITY_INVERSED;
 128 }
 129
 130 static int pwm_sifive_enable(struct pwm_chip *chip, bool enable)
 131 {
 132         struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
 133         int ret;
 134
 135         if (enable) {
 136                 ret = clk_enable(ddata->clk);
 137                 if (ret) {
 138                         dev_err(ddata->chip.dev, "Enable clk failed\n");
 139                         return ret;
 140                 }
 141         }
 142
 143         if (!enable)
 144                 clk_disable(ddata->clk);
 145
 146         return 0;
 147 }
 148
 149 static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 150                             const struct pwm_state *state)
 151 {
 152         struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
 153         struct pwm_state cur_state;
 154         unsigned int duty_cycle;
 155         unsigned long long num;
 156         bool enabled;
 157         int ret = 0;
 158         u32 frac;
 159
 160         if (state->polarity != PWM_POLARITY_INVERSED)
 161                 return -EINVAL;
 162
 163         ret = clk_enable(ddata->clk);
 164         if (ret) {
 165                 dev_err(ddata->chip.dev, "Enable clk failed\n");
 166                 return ret;
 167         }
 168
 169         mutex_lock(&ddata->lock);
 170         cur_state = pwm->state;
 171         enabled = cur_state.enabled;
 172
 173         duty_cycle = state->duty_cycle;
 174         if (!state->enabled)
 175                 duty_cycle = 0;
 176
 177         /*
 178          * The problem of output producing mixed setting as mentioned at top,
 179          * occurs here. To minimize the window for this problem, we are
 180          * calculating the register values first and then writing them
 181          * consecutively
 182          */
 183         num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
 184         frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
 185         /* The hardware cannot generate a 100% duty cycle */
 186         frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
 187
 188         if (state->period != ddata->approx_period) {
 189                 if (ddata->user_count != 1) {
 190                         ret = -EBUSY;
 191                         goto exit;
 192                 }
 193                 ddata->approx_period = state->period;
 194                 pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
 195         }
 196
 197         writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP0 +
 198                pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
 199
 200         if (state->enabled != enabled)
 201                 pwm_sifive_enable(chip, state->enabled);
 202
 203 exit:
 204         clk_disable(ddata->clk);
 205         mutex_unlock(&ddata->lock);
 206         return ret;
 207 }
 208
 209 static const struct pwm_ops pwm_sifive_ops = {
 210         .request = pwm_sifive_request,
 211         .free = pwm_sifive_free,
 212         .get_state = pwm_sifive_get_state,
 213         .apply = pwm_sifive_apply,
 214         .owner = THIS_MODULE,
 215 };
 216
 217 static int pwm_sifive_clock_notifier(struct notifier_block *nb,
 218                                      unsigned long event, void *data)
 219 {
 220         struct clk_notifier_data *ndata = data;
 221         struct pwm_sifive_ddata *ddata =
 222                 container_of(nb, struct pwm_sifive_ddata, notifier);
 223
 224         if (event == POST_RATE_CHANGE)
 225                 pwm_sifive_update_clock(ddata, ndata->new_rate);
 226
 227         return NOTIFY_OK;
 228 }
 229
 230 static int pwm_sifive_probe(struct platform_device *pdev)
 231 {
 232         struct device *dev = &pdev->dev;
 233         struct pwm_sifive_ddata *ddata;
 234         struct pwm_chip *chip;
 235         int ret;
 236
 237         ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
 238         if (!ddata)
 239                 return -ENOMEM;
 240
 241         mutex_init(&ddata->lock);
 242         chip = &ddata->chip;
 243         chip->dev = dev;
 244         chip->ops = &pwm_sifive_ops;
 245         chip->npwm = 4;
 246
 247         ddata->regs = devm_platform_ioremap_resource(pdev, 0);
 248         if (IS_ERR(ddata->regs))
 249                 return PTR_ERR(ddata->regs);
 250
 251         ddata->clk = devm_clk_get(dev, NULL);
 252         if (IS_ERR(ddata->clk))
 253                 return dev_err_probe(dev, PTR_ERR(ddata->clk),
 254                                      "Unable to find controller clock\n");
 255
 256         ret = clk_prepare_enable(ddata->clk);
 257         if (ret) {
 258                 dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
 259                 return ret;
 260         }
 261
 262         /* Watch for changes to underlying clock frequency */
 263         ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
 264         ret = clk_notifier_register(ddata->clk, &ddata->notifier);
 265         if (ret) {
 266                 dev_err(dev, "failed to register clock notifier: %d\n", ret);
 267                 goto disable_clk;
 268         }
 269
 270         ret = pwmchip_add(chip);
 271         if (ret < 0) {
 272                 dev_err(dev, "cannot register PWM: %d\n", ret);
 273                 goto unregister_clk;
 274         }
 275
 276         platform_set_drvdata(pdev, ddata);
 277         dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
 278
 279         return 0;
 280
 281 unregister_clk:
 282         clk_notifier_unregister(ddata->clk, &ddata->notifier);
 283 disable_clk:
 284         clk_disable_unprepare(ddata->clk);
 285
 286         return ret;
 287 }
 288
 289 static int pwm_sifive_remove(struct platform_device *dev)
 290 {
 291         struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
 292         bool is_enabled = false;
 293         struct pwm_device *pwm;
 294         int ret, ch;
 295
 296         for (ch = 0; ch < ddata->chip.npwm; ch++) {
 297                 pwm = &ddata->chip.pwms[ch];
 298                 if (pwm->state.enabled) {
 299                         is_enabled = true;
 300                         break;
 301                 }
 302         }
 303         if (is_enabled)
 304                 clk_disable(ddata->clk);
 305
 306         clk_disable_unprepare(ddata->clk);
 307         ret = pwmchip_remove(&ddata->chip);
 308         clk_notifier_unregister(ddata->clk, &ddata->notifier);
 309
 310         return ret;
 311 }
 312
 313 static const struct of_device_id pwm_sifive_of_match[] = {
 314         { .compatible = "sifive,pwm0" },
 315         {},
 316 };
 317 MODULE_DEVICE_TABLE(of, pwm_sifive_of_match);
 318
 319 static struct platform_driver pwm_sifive_driver = {
 320         .probe = pwm_sifive_probe,
 321         .remove = pwm_sifive_remove,
 322         .driver = {
 323                 .name = "pwm-sifive",
 324                 .of_match_table = pwm_sifive_of_match,
 325         },
 326 };
 327 module_platform_driver(pwm_sifive_driver);
 328
 329 MODULE_DESCRIPTION("SiFive PWM driver");
 330 MODULE_LICENSE("GPL v2");