drivers/pwm/pwm-lpss.c

   1 /*
   2  * Intel Low Power Subsystem PWM controller driver
   3  *
   4  * Copyright (C) 2014, Intel Corporation
   5  * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
   6  * Author: Chew Kean Ho <kean.ho.chew@intel.com>
   7  * Author: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@intel.com>
   8  * Author: Chew Chiau Ee <chiau.ee.chew@intel.com>
   9  * Author: Alan Cox <alan@linux.intel.com>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  */
  15
  16 #include <linux/delay.h>
  17 #include <linux/io.h>
  18 #include <linux/iopoll.h>
  19 #include <linux/kernel.h>
  20 #include <linux/module.h>
  21 #include <linux/pm_runtime.h>
  22 #include <linux/time.h>
  23
  24 #include "pwm-lpss.h"
  25
  26 #define PWM                             0x00000000
  27 #define PWM_ENABLE                      BIT(31)
  28 #define PWM_SW_UPDATE                   BIT(30)
  29 #define PWM_BASE_UNIT_SHIFT             8
  30 #define PWM_ON_TIME_DIV_MASK            0x000000ff
  31
  32 /* Size of each PWM register space if multiple */
  33 #define PWM_SIZE                        0x400
  34
  35 struct pwm_lpss_chip {
  36         struct pwm_chip chip;
  37         void __iomem *regs;
  38         const struct pwm_lpss_boardinfo *info;
  39 };
  40
  41 static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
  42 {
  43         return container_of(chip, struct pwm_lpss_chip, chip);
  44 }
  45
  46 static inline u32 pwm_lpss_read(const struct pwm_device *pwm)
  47 {
  48         struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
  49
  50         return readl(lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
  51 }
  52
  53 static inline void pwm_lpss_write(const struct pwm_device *pwm, u32 value)
  54 {
  55         struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
  56
  57         writel(value, lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
  58 }
  59
  60 static int pwm_lpss_wait_for_update(struct pwm_device *pwm)
  61 {
  62         struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
  63         const void __iomem *addr = lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM;
  64         const unsigned int ms = 500 * USEC_PER_MSEC;
  65         u32 val;
  66         int err;
  67
  68         /*
  69          * PWM Configuration register has SW_UPDATE bit that is set when a new
  70          * configuration is written to the register. The bit is automatically
  71          * cleared at the start of the next output cycle by the IP block.
  72          *
  73          * If one writes a new configuration to the register while it still has
  74          * the bit enabled, PWM may freeze. That is, while one can still write
  75          * to the register, it won't have an effect. Thus, we try to sleep long
  76          * enough that the bit gets cleared and make sure the bit is not
  77          * enabled while we update the configuration.
  78          */
  79         err = readl_poll_timeout(addr, val, !(val & PWM_SW_UPDATE), 40, ms);
  80         if (err)
  81                 dev_err(pwm->chip->dev, "PWM_SW_UPDATE was not cleared\n");
  82
  83         return err;
  84 }
  85
  86 static inline int pwm_lpss_is_updating(struct pwm_device *pwm)
  87 {
  88         return (pwm_lpss_read(pwm) & PWM_SW_UPDATE) ? -EBUSY : 0;
  89 }
  90
  91 static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
  92                              int duty_ns, int period_ns)
  93 {
  94         unsigned long long on_time_div;
  95         unsigned long c = lpwm->info->clk_rate, base_unit_range;
  96         unsigned long long base_unit, freq = NSEC_PER_SEC;
  97         u32 ctrl;
  98
  99         do_div(freq, period_ns);
 100
 101         /*
 102          * The equation is:
 103          * base_unit = round(base_unit_range * freq / c)
 104          */
 105         base_unit_range = BIT(lpwm->info->base_unit_bits) - 1;
 106         freq *= base_unit_range;
 107
 108         base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
 109
 110         on_time_div = 255ULL * duty_ns;
 111         do_div(on_time_div, period_ns);
 112         on_time_div = 255ULL - on_time_div;
 113
 114         ctrl = pwm_lpss_read(pwm);
 115         ctrl &= ~PWM_ON_TIME_DIV_MASK;
 116         ctrl &= ~(base_unit_range << PWM_BASE_UNIT_SHIFT);
 117         base_unit &= base_unit_range;
 118         ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
 119         ctrl |= on_time_div;
 120         pwm_lpss_write(pwm, ctrl);
 121 }
 122
 123 static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
 124 {
 125         if (cond)
 126                 pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
 127 }
 128
 129 static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 130                           struct pwm_state *state)
 131 {
 132         struct pwm_lpss_chip *lpwm = to_lpwm(chip);
 133         int ret;
 134
 135         if (state->enabled) {
 136                 if (!pwm_is_enabled(pwm)) {
 137                         pm_runtime_get_sync(chip->dev);
 138                         ret = pwm_lpss_is_updating(pwm);
 139                         if (ret) {
 140                                 pm_runtime_put(chip->dev);
 141                                 return ret;
 142                         }
 143                         pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
 144                         pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
 145                         pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
 146                         ret = pwm_lpss_wait_for_update(pwm);
 147                         if (ret) {
 148                                 pm_runtime_put(chip->dev);
 149                                 return ret;
 150                         }
 151                         pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
 152                 } else {
 153                         ret = pwm_lpss_is_updating(pwm);
 154                         if (ret)
 155                                 return ret;
 156                         pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
 157                         pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_SW_UPDATE);
 158                         return pwm_lpss_wait_for_update(pwm);
 159                 }
 160         } else if (pwm_is_enabled(pwm)) {
 161                 pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
 162                 pm_runtime_put(chip->dev);
 163         }
 164
 165         return 0;
 166 }
 167
 168 static const struct pwm_ops pwm_lpss_ops = {
 169         .apply = pwm_lpss_apply,
 170         .owner = THIS_MODULE,
 171 };
 172
 173 struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
 174                                      const struct pwm_lpss_boardinfo *info)
 175 {
 176         struct pwm_lpss_chip *lpwm;
 177         unsigned long c;
 178         int ret;
 179
 180         lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
 181         if (!lpwm)
 182                 return ERR_PTR(-ENOMEM);
 183
 184         lpwm->regs = devm_ioremap_resource(dev, r);
 185         if (IS_ERR(lpwm->regs))
 186                 return ERR_CAST(lpwm->regs);
 187
 188         lpwm->info = info;
 189
 190         c = lpwm->info->clk_rate;
 191         if (!c)
 192                 return ERR_PTR(-EINVAL);
 193
 194         lpwm->chip.dev = dev;
 195         lpwm->chip.ops = &pwm_lpss_ops;
 196         lpwm->chip.base = -1;
 197         lpwm->chip.npwm = info->npwm;
 198
 199         ret = pwmchip_add(&lpwm->chip);
 200         if (ret) {
 201                 dev_err(dev, "failed to add PWM chip: %d\n", ret);
 202                 return ERR_PTR(ret);
 203         }
 204
 205         return lpwm;
 206 }
 207 EXPORT_SYMBOL_GPL(pwm_lpss_probe);
 208
 209 int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
 210 {
 211         return pwmchip_remove(&lpwm->chip);
 212 }
 213 EXPORT_SYMBOL_GPL(pwm_lpss_remove);
 214
 215 MODULE_DESCRIPTION("PWM driver for Intel LPSS");
 216 MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
 217 MODULE_LICENSE("GPL v2");