drivers/pwm/pwm-stmpe.c

   1 /*
   2  * Copyright (C) 2016 Linaro Ltd.
   3  *
   4  * Author: Linus Walleij <linus.walleij@linaro.org>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2, as
   8  * published by the Free Software Foundation.
   9  *
  10  */
  11
  12 #include <linux/bitops.h>
  13 #include <linux/delay.h>
  14 #include <linux/err.h>
  15 #include <linux/mfd/stmpe.h>
  16 #include <linux/module.h>
  17 #include <linux/of.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/pwm.h>
  20 #include <linux/slab.h>
  21
  22 #define STMPE24XX_PWMCS         0x30
  23 #define PWMCS_EN_PWM0           BIT(0)
  24 #define PWMCS_EN_PWM1           BIT(1)
  25 #define PWMCS_EN_PWM2           BIT(2)
  26 #define STMPE24XX_PWMIC0        0x38
  27 #define STMPE24XX_PWMIC1        0x39
  28 #define STMPE24XX_PWMIC2        0x3a
  29
  30 #define STMPE_PWM_24XX_PINBASE  21
  31
  32 struct stmpe_pwm {
  33         struct stmpe *stmpe;
  34         struct pwm_chip chip;
  35         u8 last_duty;
  36 };
  37
  38 static inline struct stmpe_pwm *to_stmpe_pwm(struct pwm_chip *chip)
  39 {
  40         return container_of(chip, struct stmpe_pwm, chip);
  41 }
  42
  43 static int stmpe_24xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  44 {
  45         struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
  46         u8 value;
  47         int ret;
  48
  49         ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
  50         if (ret < 0) {
  51                 dev_err(chip->dev, "error reading PWM#%u control\n",
  52                         pwm->hwpwm);
  53                 return ret;
  54         }
  55
  56         value = ret | BIT(pwm->hwpwm);
  57
  58         ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
  59         if (ret) {
  60                 dev_err(chip->dev, "error writing PWM#%u control\n",
  61                         pwm->hwpwm);
  62                 return ret;
  63         }
  64
  65         return 0;
  66 }
  67
  68 static void stmpe_24xx_pwm_disable(struct pwm_chip *chip,
  69                                    struct pwm_device *pwm)
  70 {
  71         struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
  72         u8 value;
  73         int ret;
  74
  75         ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
  76         if (ret < 0) {
  77                 dev_err(chip->dev, "error reading PWM#%u control\n",
  78                         pwm->hwpwm);
  79                 return;
  80         }
  81
  82         value = ret & ~BIT(pwm->hwpwm);
  83
  84         ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
  85         if (ret) {
  86                 dev_err(chip->dev, "error writing PWM#%u control\n",
  87                         pwm->hwpwm);
  88                 return;
  89         }
  90 }
  91
  92 /* STMPE 24xx PWM instructions */
  93 #define SMAX            0x007f
  94 #define SMIN            0x00ff
  95 #define GTS             0x0000
  96 #define LOAD            BIT(14) /* Only available on 2403 */
  97 #define RAMPUP          0x0000
  98 #define RAMPDOWN        BIT(7)
  99 #define PRESCALE_512    BIT(14)
 100 #define STEPTIME_1      BIT(8)
 101 #define BRANCH          (BIT(15) | BIT(13))
 102
 103 static int stmpe_24xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 104                                  int duty_ns, int period_ns)
 105 {
 106         struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
 107         unsigned int i, pin;
 108         u16 program[3] = {
 109                 SMAX,
 110                 GTS,
 111                 GTS,
 112         };
 113         u8 offset;
 114         int ret;
 115
 116         /* Make sure we are disabled */
 117         if (pwm_is_enabled(pwm)) {
 118                 stmpe_24xx_pwm_disable(chip, pwm);
 119         } else {
 120                 /* Connect the PWM to the pin */
 121                 pin = pwm->hwpwm;
 122
 123                 /* On STMPE2401 and 2403 pins 21,22,23 are used */
 124                 if (stmpe_pwm->stmpe->partnum == STMPE2401 ||
 125                     stmpe_pwm->stmpe->partnum == STMPE2403)
 126                         pin += STMPE_PWM_24XX_PINBASE;
 127
 128                 ret = stmpe_set_altfunc(stmpe_pwm->stmpe, BIT(pin),
 129                                         STMPE_BLOCK_PWM);
 130                 if (ret) {
 131                         dev_err(chip->dev, "unable to connect PWM#%u to pin\n",
 132                                 pwm->hwpwm);
 133                         return ret;
 134                 }
 135         }
 136
 137         /* STMPE24XX */
 138         switch (pwm->hwpwm) {
 139         case 0:
 140                 offset = STMPE24XX_PWMIC0;
 141                 break;
 142
 143         case 1:
 144                 offset = STMPE24XX_PWMIC1;
 145                 break;
 146
 147         case 2:
 148                 offset = STMPE24XX_PWMIC2;
 149                 break;
 150
 151         default:
 152                 /* Should not happen as npwm is 3 */
 153                 return -ENODEV;
 154         }
 155
 156         dev_dbg(chip->dev, "PWM#%u: config duty %d ns, period %d ns\n",
 157                 pwm->hwpwm, duty_ns, period_ns);
 158
 159         if (duty_ns == 0) {
 160                 if (stmpe_pwm->stmpe->partnum == STMPE2401)
 161                         program[0] = SMAX; /* off all the time */
 162
 163                 if (stmpe_pwm->stmpe->partnum == STMPE2403)
 164                         program[0] = LOAD | 0xff; /* LOAD 0xff */
 165
 166                 stmpe_pwm->last_duty = 0x00;
 167         } else if (duty_ns == period_ns) {
 168                 if (stmpe_pwm->stmpe->partnum == STMPE2401)
 169                         program[0] = SMIN; /* on all the time */
 170
 171                 if (stmpe_pwm->stmpe->partnum == STMPE2403)
 172                         program[0] = LOAD | 0x00; /* LOAD 0x00 */
 173
 174                 stmpe_pwm->last_duty = 0xff;
 175         } else {
 176                 u8 value, last = stmpe_pwm->last_duty;
 177                 unsigned long duty;
 178
 179                 /*
 180                  * Counter goes from 0x00 to 0xff repeatedly at 32768 Hz,
 181                  * (means a period of 30517 ns) then this is compared to the
 182                  * counter from the ramp, if this is >= PWM counter the output
 183                  * is high. With LOAD we can define how much of the cycle it
 184                  * is on.
 185                  *
 186                  * Prescale = 0 -> 2 kHz -> T = 1/f = 488281.25 ns
 187                  */
 188
 189                 /* Scale to 0..0xff */
 190                 duty = duty_ns * 256;
 191                 duty = DIV_ROUND_CLOSEST(duty, period_ns);
 192                 value = duty;
 193
 194                 if (value == last) {
 195                         /* Run the old program */
 196                         if (pwm_is_enabled(pwm))
 197                                 stmpe_24xx_pwm_enable(chip, pwm);
 198
 199                         return 0;
 200                 } else if (stmpe_pwm->stmpe->partnum == STMPE2403) {
 201                         /* STMPE2403 can simply set the right PWM value */
 202                         program[0] = LOAD | value;
 203                         program[1] = 0x0000;
 204                 } else if (stmpe_pwm->stmpe->partnum == STMPE2401) {
 205                         /* STMPE2401 need a complex program */
 206                         u16 incdec = 0x0000;
 207
 208                         if (last < value)
 209                                 /* Count up */
 210                                 incdec = RAMPUP | (value - last);
 211                         else
 212                                 /* Count down */
 213                                 incdec = RAMPDOWN | (last - value);
 214
 215                         /* Step to desired value, smoothly */
 216                         program[0] = PRESCALE_512 | STEPTIME_1 | incdec;
 217
 218                         /* Loop eternally to 0x00 */
 219                         program[1] = BRANCH;
 220                 }
 221
 222                 dev_dbg(chip->dev,
 223                         "PWM#%u: value = %02x, last_duty = %02x, program=%04x,%04x,%04x\n",
 224                         pwm->hwpwm, value, last, program[0], program[1],
 225                         program[2]);
 226                 stmpe_pwm->last_duty = value;
 227         }
 228
 229         /*
 230          * We can write programs of up to 64 16-bit words into this channel.
 231          */
 232         for (i = 0; i < ARRAY_SIZE(program); i++) {
 233                 u8 value;
 234
 235                 value = (program[i] >> 8) & 0xff;
 236
 237                 ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
 238                 if (ret) {
 239                         dev_err(chip->dev, "error writing register %02x: %d\n",
 240                                 offset, ret);
 241                         return ret;
 242                 }
 243
 244                 value = program[i] & 0xff;
 245
 246                 ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
 247                 if (ret) {
 248                         dev_err(chip->dev, "error writing register %02x: %d\n",
 249                                 offset, ret);
 250                         return ret;
 251                 }
 252         }
 253
 254         /* If we were enabled, re-enable this PWM */
 255         if (pwm_is_enabled(pwm))
 256                 stmpe_24xx_pwm_enable(chip, pwm);
 257
 258         /* Sleep for 200ms so we're sure it will take effect */
 259         msleep(200);
 260
 261         dev_dbg(chip->dev, "programmed PWM#%u, %u bytes\n", pwm->hwpwm, i);
 262
 263         return 0;
 264 }
 265
 266 static const struct pwm_ops stmpe_24xx_pwm_ops = {
 267         .config = stmpe_24xx_pwm_config,
 268         .enable = stmpe_24xx_pwm_enable,
 269         .disable = stmpe_24xx_pwm_disable,
 270         .owner = THIS_MODULE,
 271 };
 272
 273 static int __init stmpe_pwm_probe(struct platform_device *pdev)
 274 {
 275         struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent);
 276         struct stmpe_pwm *pwm;
 277         int ret;
 278
 279         pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
 280         if (!pwm)
 281                 return -ENOMEM;
 282
 283         pwm->stmpe = stmpe;
 284         pwm->chip.dev = &pdev->dev;
 285         pwm->chip.base = -1;
 286
 287         if (stmpe->partnum == STMPE2401 || stmpe->partnum == STMPE2403) {
 288                 pwm->chip.ops = &stmpe_24xx_pwm_ops;
 289                 pwm->chip.npwm = 3;
 290         } else {
 291                 if (stmpe->partnum == STMPE1601)
 292                         dev_err(&pdev->dev, "STMPE1601 not yet supported\n");
 293                 else
 294                         dev_err(&pdev->dev, "Unknown STMPE PWM\n");
 295
 296                 return -ENODEV;
 297         }
 298
 299         ret = stmpe_enable(stmpe, STMPE_BLOCK_PWM);
 300         if (ret)
 301                 return ret;
 302
 303         ret = pwmchip_add(&pwm->chip);
 304         if (ret) {
 305                 stmpe_disable(stmpe, STMPE_BLOCK_PWM);
 306                 return ret;
 307         }
 308
 309         platform_set_drvdata(pdev, pwm);
 310
 311         return 0;
 312 }
 313
 314 static struct platform_driver stmpe_pwm_driver = {
 315         .driver = {
 316                 .name = "stmpe-pwm",
 317         },
 318 };
 319 builtin_platform_driver_probe(stmpe_pwm_driver, stmpe_pwm_probe);