drivers/pwm/pwm-spear.c

   1 /*
   2  * ST Microelectronics SPEAr Pulse Width Modulator driver
   3  *
   4  * Copyright (C) 2012 ST Microelectronics
   5  * Shiraz Hashim <shiraz.linux.kernel@gmail.com>
   6  *
   7  * This file is licensed under the terms of the GNU General Public
   8  * License version 2. This program is licensed "as is" without any
   9  * warranty of any kind, whether express or implied.
  10  */
  11
  12 #include <linux/clk.h>
  13 #include <linux/err.h>
  14 #include <linux/io.h>
  15 #include <linux/ioport.h>
  16 #include <linux/kernel.h>
  17 #include <linux/math64.h>
  18 #include <linux/module.h>
  19 #include <linux/of.h>
  20 #include <linux/platform_device.h>
  21 #include <linux/pwm.h>
  22 #include <linux/slab.h>
  23 #include <linux/types.h>
  24
  25 #define NUM_PWM         4
  26
  27 /* PWM registers and bits definitions */
  28 #define PWMCR                   0x00    /* Control Register */
  29 #define PWMCR_PWM_ENABLE        0x1
  30 #define PWMCR_PRESCALE_SHIFT    2
  31 #define PWMCR_MIN_PRESCALE      0x00
  32 #define PWMCR_MAX_PRESCALE      0x3FFF
  33
  34 #define PWMDCR                  0x04    /* Duty Cycle Register */
  35 #define PWMDCR_MIN_DUTY         0x0001
  36 #define PWMDCR_MAX_DUTY         0xFFFF
  37
  38 #define PWMPCR                  0x08    /* Period Register */
  39 #define PWMPCR_MIN_PERIOD       0x0001
  40 #define PWMPCR_MAX_PERIOD       0xFFFF
  41
  42 /* Following only available on 13xx SoCs */
  43 #define PWMMCR                  0x3C    /* Master Control Register */
  44 #define PWMMCR_PWM_ENABLE       0x1
  45
  46 /**
  47  * struct spear_pwm_chip - struct representing pwm chip
  48  *
  49  * @mmio_base: base address of pwm chip
  50  * @clk: pointer to clk structure of pwm chip
  51  * @chip: linux pwm chip representation
  52  */
  53 struct spear_pwm_chip {
  54         void __iomem *mmio_base;
  55         struct clk *clk;
  56         struct pwm_chip chip;
  57 };
  58
  59 static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)
  60 {
  61         return container_of(chip, struct spear_pwm_chip, chip);
  62 }
  63
  64 static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num,
  65                                   unsigned long offset)
  66 {
  67         return readl_relaxed(chip->mmio_base + (num << 4) + offset);
  68 }
  69
  70 static inline void spear_pwm_writel(struct spear_pwm_chip *chip,
  71                                     unsigned int num, unsigned long offset,
  72                                     unsigned long val)
  73 {
  74         writel_relaxed(val, chip->mmio_base + (num << 4) + offset);
  75 }
  76
  77 static int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  78                             u64 duty_ns, u64 period_ns)
  79 {
  80         struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
  81         u64 val, div, clk_rate;
  82         unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc;
  83         int ret;
  84
  85         /*
  86          * Find pv, dc and prescale to suit duty_ns and period_ns. This is done
  87          * according to formulas described below:
  88          *
  89          * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE
  90          * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
  91          *
  92          * PV = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
  93          * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
  94          */
  95         clk_rate = clk_get_rate(pc->clk);
  96         while (1) {
  97                 div = 1000000000;
  98                 div *= 1 + prescale;
  99                 val = clk_rate * period_ns;
 100                 pv = div64_u64(val, div);
 101                 val = clk_rate * duty_ns;
 102                 dc = div64_u64(val, div);
 103
 104                 /* if duty_ns and period_ns are not achievable then return */
 105                 if (pv < PWMPCR_MIN_PERIOD || dc < PWMDCR_MIN_DUTY)
 106                         return -EINVAL;
 107
 108                 /*
 109                  * if pv and dc have crossed their upper limit, then increase
 110                  * prescale and recalculate pv and dc.
 111                  */
 112                 if (pv > PWMPCR_MAX_PERIOD || dc > PWMDCR_MAX_DUTY) {
 113                         if (++prescale > PWMCR_MAX_PRESCALE)
 114                                 return -EINVAL;
 115                         continue;
 116                 }
 117                 break;
 118         }
 119
 120         /*
 121          * NOTE: the clock to PWM has to be enabled first before writing to the
 122          * registers.
 123          */
 124         ret = clk_enable(pc->clk);
 125         if (ret)
 126                 return ret;
 127
 128         spear_pwm_writel(pc, pwm->hwpwm, PWMCR,
 129                         prescale << PWMCR_PRESCALE_SHIFT);
 130         spear_pwm_writel(pc, pwm->hwpwm, PWMDCR, dc);
 131         spear_pwm_writel(pc, pwm->hwpwm, PWMPCR, pv);
 132         clk_disable(pc->clk);
 133
 134         return 0;
 135 }
 136
 137 static int spear_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 138 {
 139         struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
 140         int rc = 0;
 141         u32 val;
 142
 143         rc = clk_enable(pc->clk);
 144         if (rc)
 145                 return rc;
 146
 147         val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
 148         val |= PWMCR_PWM_ENABLE;
 149         spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
 150
 151         return 0;
 152 }
 153
 154 static void spear_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 155 {
 156         struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
 157         u32 val;
 158
 159         val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
 160         val &= ~PWMCR_PWM_ENABLE;
 161         spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
 162
 163         clk_disable(pc->clk);
 164 }
 165
 166 static int spear_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 167                            const struct pwm_state *state)
 168 {
 169         int err;
 170
 171         if (state->polarity != PWM_POLARITY_NORMAL)
 172                 return -EINVAL;
 173
 174         if (!state->enabled) {
 175                 if (pwm->state.enabled)
 176                         spear_pwm_disable(chip, pwm);
 177                 return 0;
 178         }
 179
 180         if (state->period != pwm->state.period ||
 181             state->duty_cycle != pwm->state.duty_cycle) {
 182                 err = spear_pwm_config(chip, pwm, state->duty_cycle, state->period);
 183                 if (err)
 184                         return err;
 185         }
 186
 187         if (!pwm->state.enabled)
 188                 return spear_pwm_enable(chip, pwm);
 189
 190         return 0;
 191 }
 192
 193 static const struct pwm_ops spear_pwm_ops = {
 194         .apply = spear_pwm_apply,
 195         .owner = THIS_MODULE,
 196 };
 197
 198 static int spear_pwm_probe(struct platform_device *pdev)
 199 {
 200         struct device_node *np = pdev->dev.of_node;
 201         struct spear_pwm_chip *pc;
 202         int ret;
 203         u32 val;
 204
 205         pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
 206         if (!pc)
 207                 return -ENOMEM;
 208
 209         pc->mmio_base = devm_platform_ioremap_resource(pdev, 0);
 210         if (IS_ERR(pc->mmio_base))
 211                 return PTR_ERR(pc->mmio_base);
 212
 213         pc->clk = devm_clk_get(&pdev->dev, NULL);
 214         if (IS_ERR(pc->clk))
 215                 return PTR_ERR(pc->clk);
 216
 217         platform_set_drvdata(pdev, pc);
 218
 219         pc->chip.dev = &pdev->dev;
 220         pc->chip.ops = &spear_pwm_ops;
 221         pc->chip.npwm = NUM_PWM;
 222
 223         ret = clk_prepare(pc->clk);
 224         if (ret)
 225                 return ret;
 226
 227         if (of_device_is_compatible(np, "st,spear1340-pwm")) {
 228                 ret = clk_enable(pc->clk);
 229                 if (ret) {
 230                         clk_unprepare(pc->clk);
 231                         return ret;
 232                 }
 233                 /*
 234                  * Following enables PWM chip, channels would still be
 235                  * enabled individually through their control register
 236                  */
 237                 val = readl_relaxed(pc->mmio_base + PWMMCR);
 238                 val |= PWMMCR_PWM_ENABLE;
 239                 writel_relaxed(val, pc->mmio_base + PWMMCR);
 240
 241                 clk_disable(pc->clk);
 242         }
 243
 244         ret = pwmchip_add(&pc->chip);
 245         if (ret < 0) {
 246                 clk_unprepare(pc->clk);
 247                 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 248         }
 249
 250         return ret;
 251 }
 252
 253 static int spear_pwm_remove(struct platform_device *pdev)
 254 {
 255         struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
 256
 257         pwmchip_remove(&pc->chip);
 258
 259         /* clk was prepared in probe, hence unprepare it here */
 260         clk_unprepare(pc->clk);
 261
 262         return 0;
 263 }
 264
 265 static const struct of_device_id spear_pwm_of_match[] = {
 266         { .compatible = "st,spear320-pwm" },
 267         { .compatible = "st,spear1340-pwm" },
 268         { }
 269 };
 270
 271 MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
 272
 273 static struct platform_driver spear_pwm_driver = {
 274         .driver = {
 275                 .name = "spear-pwm",
 276                 .of_match_table = spear_pwm_of_match,
 277         },
 278         .probe = spear_pwm_probe,
 279         .remove = spear_pwm_remove,
 280 };
 281
 282 module_platform_driver(spear_pwm_driver);
 283
 284 MODULE_LICENSE("GPL");
 285 MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>");
 286 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
 287 MODULE_ALIAS("platform:spear-pwm");