drivers/pwm/pwm-imx27.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * simple driver for PWM (Pulse Width Modulator) controller
   4  *
   5  * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
   6  *
   7  * Limitations:
   8  * - When disabled the output is driven to 0 independent of the configured
   9  *   polarity.
  10  */
  11
  12 #include <linux/bitfield.h>
  13 #include <linux/bitops.h>
  14 #include <linux/clk.h>
  15 #include <linux/delay.h>
  16 #include <linux/err.h>
  17 #include <linux/io.h>
  18 #include <linux/kernel.h>
  19 #include <linux/module.h>
  20 #include <linux/of.h>
  21 #include <linux/platform_device.h>
  22 #include <linux/pwm.h>
  23 #include <linux/slab.h>
  24
  25 #define MX3_PWMCR                       0x00    /* PWM Control Register */
  26 #define MX3_PWMSR                       0x04    /* PWM Status Register */
  27 #define MX3_PWMSAR                      0x0C    /* PWM Sample Register */
  28 #define MX3_PWMPR                       0x10    /* PWM Period Register */
  29
  30 #define MX3_PWMCR_FWM                   GENMASK(27, 26)
  31 #define MX3_PWMCR_STOPEN                BIT(25)
  32 #define MX3_PWMCR_DOZEN                 BIT(24)
  33 #define MX3_PWMCR_WAITEN                BIT(23)
  34 #define MX3_PWMCR_DBGEN                 BIT(22)
  35 #define MX3_PWMCR_BCTR                  BIT(21)
  36 #define MX3_PWMCR_HCTR                  BIT(20)
  37
  38 #define MX3_PWMCR_POUTC                 GENMASK(19, 18)
  39 #define MX3_PWMCR_POUTC_NORMAL          0
  40 #define MX3_PWMCR_POUTC_INVERTED        1
  41 #define MX3_PWMCR_POUTC_OFF             2
  42
  43 #define MX3_PWMCR_CLKSRC                GENMASK(17, 16)
  44 #define MX3_PWMCR_CLKSRC_OFF            0
  45 #define MX3_PWMCR_CLKSRC_IPG            1
  46 #define MX3_PWMCR_CLKSRC_IPG_HIGH       2
  47 #define MX3_PWMCR_CLKSRC_IPG_32K        3
  48
  49 #define MX3_PWMCR_PRESCALER             GENMASK(15, 4)
  50
  51 #define MX3_PWMCR_SWR                   BIT(3)
  52
  53 #define MX3_PWMCR_REPEAT                GENMASK(2, 1)
  54 #define MX3_PWMCR_REPEAT_1X             0
  55 #define MX3_PWMCR_REPEAT_2X             1
  56 #define MX3_PWMCR_REPEAT_4X             2
  57 #define MX3_PWMCR_REPEAT_8X             3
  58
  59 #define MX3_PWMCR_EN                    BIT(0)
  60
  61 #define MX3_PWMSR_FWE                   BIT(6)
  62 #define MX3_PWMSR_CMP                   BIT(5)
  63 #define MX3_PWMSR_ROV                   BIT(4)
  64 #define MX3_PWMSR_FE                    BIT(3)
  65
  66 #define MX3_PWMSR_FIFOAV                GENMASK(2, 0)
  67 #define MX3_PWMSR_FIFOAV_EMPTY          0
  68 #define MX3_PWMSR_FIFOAV_1WORD          1
  69 #define MX3_PWMSR_FIFOAV_2WORDS         2
  70 #define MX3_PWMSR_FIFOAV_3WORDS         3
  71 #define MX3_PWMSR_FIFOAV_4WORDS         4
  72
  73 #define MX3_PWMCR_PRESCALER_SET(x)      FIELD_PREP(MX3_PWMCR_PRESCALER, (x) - 1)
  74 #define MX3_PWMCR_PRESCALER_GET(x)      (FIELD_GET(MX3_PWMCR_PRESCALER, \
  75                                                    (x)) + 1)
  76
  77 #define MX3_PWM_SWR_LOOP                5
  78
  79 /* PWMPR register value of 0xffff has the same effect as 0xfffe */
  80 #define MX3_PWMPR_MAX                   0xfffe
  81
  82 struct pwm_imx27_chip {
  83         struct clk      *clk_ipg;
  84         struct clk      *clk_per;
  85         void __iomem    *mmio_base;
  86         struct pwm_chip chip;
  87
  88         /*
  89          * The driver cannot read the current duty cycle from the hardware if
  90          * the hardware is disabled. Cache the last programmed duty cycle
  91          * value to return in that case.
  92          */
  93         unsigned int duty_cycle;
  94 };
  95
  96 #define to_pwm_imx27_chip(chip) container_of(chip, struct pwm_imx27_chip, chip)
  97
  98 static int pwm_imx27_clk_prepare_enable(struct pwm_imx27_chip *imx)
  99 {
 100         int ret;
 101
 102         ret = clk_prepare_enable(imx->clk_ipg);
 103         if (ret)
 104                 return ret;
 105
 106         ret = clk_prepare_enable(imx->clk_per);
 107         if (ret) {
 108                 clk_disable_unprepare(imx->clk_ipg);
 109                 return ret;
 110         }
 111
 112         return 0;
 113 }
 114
 115 static void pwm_imx27_clk_disable_unprepare(struct pwm_imx27_chip *imx)
 116 {
 117         clk_disable_unprepare(imx->clk_per);
 118         clk_disable_unprepare(imx->clk_ipg);
 119 }
 120
 121 static void pwm_imx27_get_state(struct pwm_chip *chip,
 122                                 struct pwm_device *pwm, struct pwm_state *state)
 123 {
 124         struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
 125         u32 period, prescaler, pwm_clk, val;
 126         u64 tmp;
 127         int ret;
 128
 129         ret = pwm_imx27_clk_prepare_enable(imx);
 130         if (ret < 0)
 131                 return;
 132
 133         val = readl(imx->mmio_base + MX3_PWMCR);
 134
 135         if (val & MX3_PWMCR_EN)
 136                 state->enabled = true;
 137         else
 138                 state->enabled = false;
 139
 140         switch (FIELD_GET(MX3_PWMCR_POUTC, val)) {
 141         case MX3_PWMCR_POUTC_NORMAL:
 142                 state->polarity = PWM_POLARITY_NORMAL;
 143                 break;
 144         case MX3_PWMCR_POUTC_INVERTED:
 145                 state->polarity = PWM_POLARITY_INVERSED;
 146                 break;
 147         default:
 148                 dev_warn(chip->dev, "can't set polarity, output disconnected");
 149         }
 150
 151         prescaler = MX3_PWMCR_PRESCALER_GET(val);
 152         pwm_clk = clk_get_rate(imx->clk_per);
 153         val = readl(imx->mmio_base + MX3_PWMPR);
 154         period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
 155
 156         /* PWMOUT (Hz) = PWMCLK / (PWMPR + 2) */
 157         tmp = NSEC_PER_SEC * (u64)(period + 2) * prescaler;
 158         state->period = DIV_ROUND_UP_ULL(tmp, pwm_clk);
 159
 160         /*
 161          * PWMSAR can be read only if PWM is enabled. If the PWM is disabled,
 162          * use the cached value.
 163          */
 164         if (state->enabled)
 165                 val = readl(imx->mmio_base + MX3_PWMSAR);
 166         else
 167                 val = imx->duty_cycle;
 168
 169         tmp = NSEC_PER_SEC * (u64)(val) * prescaler;
 170         state->duty_cycle = DIV_ROUND_UP_ULL(tmp, pwm_clk);
 171
 172         pwm_imx27_clk_disable_unprepare(imx);
 173 }
 174
 175 static void pwm_imx27_sw_reset(struct pwm_chip *chip)
 176 {
 177         struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
 178         struct device *dev = chip->dev;
 179         int wait_count = 0;
 180         u32 cr;
 181
 182         writel(MX3_PWMCR_SWR, imx->mmio_base + MX3_PWMCR);
 183         do {
 184                 usleep_range(200, 1000);
 185                 cr = readl(imx->mmio_base + MX3_PWMCR);
 186         } while ((cr & MX3_PWMCR_SWR) &&
 187                  (wait_count++ < MX3_PWM_SWR_LOOP));
 188
 189         if (cr & MX3_PWMCR_SWR)
 190                 dev_warn(dev, "software reset timeout\n");
 191 }
 192
 193 static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
 194                                      struct pwm_device *pwm)
 195 {
 196         struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
 197         struct device *dev = chip->dev;
 198         unsigned int period_ms;
 199         int fifoav;
 200         u32 sr;
 201
 202         sr = readl(imx->mmio_base + MX3_PWMSR);
 203         fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr);
 204         if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) {
 205                 period_ms = DIV_ROUND_UP_ULL(pwm_get_period(pwm),
 206                                          NSEC_PER_MSEC);
 207                 msleep(period_ms);
 208
 209                 sr = readl(imx->mmio_base + MX3_PWMSR);
 210                 if (fifoav == FIELD_GET(MX3_PWMSR_FIFOAV, sr))
 211                         dev_warn(dev, "there is no free FIFO slot\n");
 212         }
 213 }
 214
 215 static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 216                            const struct pwm_state *state)
 217 {
 218         unsigned long period_cycles, duty_cycles, prescale;
 219         struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
 220         struct pwm_state cstate;
 221         unsigned long long c;
 222         unsigned long long clkrate;
 223         int ret;
 224         u32 cr;
 225
 226         pwm_get_state(pwm, &cstate);
 227
 228         clkrate = clk_get_rate(imx->clk_per);
 229         c = clkrate * state->period;
 230
 231         do_div(c, NSEC_PER_SEC);
 232         period_cycles = c;
 233
 234         prescale = period_cycles / 0x10000 + 1;
 235
 236         period_cycles /= prescale;
 237         c = clkrate * state->duty_cycle;
 238         do_div(c, NSEC_PER_SEC);
 239         duty_cycles = c;
 240         duty_cycles /= prescale;
 241
 242         /*
 243          * according to imx pwm RM, the real period value should be PERIOD
 244          * value in PWMPR plus 2.
 245          */
 246         if (period_cycles > 2)
 247                 period_cycles -= 2;
 248         else
 249                 period_cycles = 0;
 250
 251         /*
 252          * Wait for a free FIFO slot if the PWM is already enabled, and flush
 253          * the FIFO if the PWM was disabled and is about to be enabled.
 254          */
 255         if (cstate.enabled) {
 256                 pwm_imx27_wait_fifo_slot(chip, pwm);
 257         } else {
 258                 ret = pwm_imx27_clk_prepare_enable(imx);
 259                 if (ret)
 260                         return ret;
 261
 262                 pwm_imx27_sw_reset(chip);
 263         }
 264
 265         writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
 266         writel(period_cycles, imx->mmio_base + MX3_PWMPR);
 267
 268         /*
 269          * Store the duty cycle for future reference in cases where the
 270          * MX3_PWMSAR register can't be read (i.e. when the PWM is disabled).
 271          */
 272         imx->duty_cycle = duty_cycles;
 273
 274         cr = MX3_PWMCR_PRESCALER_SET(prescale) |
 275              MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
 276              FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) |
 277              MX3_PWMCR_DBGEN;
 278
 279         if (state->polarity == PWM_POLARITY_INVERSED)
 280                 cr |= FIELD_PREP(MX3_PWMCR_POUTC,
 281                                 MX3_PWMCR_POUTC_INVERTED);
 282
 283         if (state->enabled)
 284                 cr |= MX3_PWMCR_EN;
 285
 286         writel(cr, imx->mmio_base + MX3_PWMCR);
 287
 288         if (!state->enabled)
 289                 pwm_imx27_clk_disable_unprepare(imx);
 290
 291         return 0;
 292 }
 293
 294 static const struct pwm_ops pwm_imx27_ops = {
 295         .apply = pwm_imx27_apply,
 296         .get_state = pwm_imx27_get_state,
 297         .owner = THIS_MODULE,
 298 };
 299
 300 static const struct of_device_id pwm_imx27_dt_ids[] = {
 301         { .compatible = "fsl,imx27-pwm", },
 302         { /* sentinel */ }
 303 };
 304 MODULE_DEVICE_TABLE(of, pwm_imx27_dt_ids);
 305
 306 static int pwm_imx27_probe(struct platform_device *pdev)
 307 {
 308         struct pwm_imx27_chip *imx;
 309         int ret;
 310         u32 pwmcr;
 311
 312         imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
 313         if (imx == NULL)
 314                 return -ENOMEM;
 315
 316         imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
 317         if (IS_ERR(imx->clk_ipg))
 318                 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg),
 319                                      "getting ipg clock failed\n");
 320
 321         imx->clk_per = devm_clk_get(&pdev->dev, "per");
 322         if (IS_ERR(imx->clk_per))
 323                 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per),
 324                                      "failed to get peripheral clock\n");
 325
 326         imx->chip.ops = &pwm_imx27_ops;
 327         imx->chip.dev = &pdev->dev;
 328         imx->chip.npwm = 1;
 329
 330         imx->mmio_base = devm_platform_ioremap_resource(pdev, 0);
 331         if (IS_ERR(imx->mmio_base))
 332                 return PTR_ERR(imx->mmio_base);
 333
 334         ret = pwm_imx27_clk_prepare_enable(imx);
 335         if (ret)
 336                 return ret;
 337
 338         /* keep clks on if pwm is running */
 339         pwmcr = readl(imx->mmio_base + MX3_PWMCR);
 340         if (!(pwmcr & MX3_PWMCR_EN))
 341                 pwm_imx27_clk_disable_unprepare(imx);
 342
 343         return devm_pwmchip_add(&pdev->dev, &imx->chip);
 344 }
 345
 346 static struct platform_driver imx_pwm_driver = {
 347         .driver = {
 348                 .name = "pwm-imx27",
 349                 .of_match_table = pwm_imx27_dt_ids,
 350         },
 351         .probe = pwm_imx27_probe,
 352 };
 353 module_platform_driver(imx_pwm_driver);
 354
 355 MODULE_LICENSE("GPL v2");
 356 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");