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 #define MAX_PWMS                        4
  36
  37 struct pwm_lpss_chip {
  38         struct pwm_chip chip;
  39         void __iomem *regs;
  40         const struct pwm_lpss_boardinfo *info;
  41         u32 saved_ctrl[MAX_PWMS];
  42 };
  43
  44 static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
  45 {
  46         return container_of(chip, struct pwm_lpss_chip, chip);
  47 }
  48
  49 static inline u32 pwm_lpss_read(const struct pwm_device *pwm)
  50 {
  51         struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
  52
  53         return readl(lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
  54 }
  55
  56 static inline void pwm_lpss_write(const struct pwm_device *pwm, u32 value)
  57 {
  58         struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
  59
  60         writel(value, lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM);
  61 }
  62
  63 static int pwm_lpss_wait_for_update(struct pwm_device *pwm)
  64 {
  65         struct pwm_lpss_chip *lpwm = to_lpwm(pwm->chip);
  66         const void __iomem *addr = lpwm->regs + pwm->hwpwm * PWM_SIZE + PWM;
  67         const unsigned int ms = 500 * USEC_PER_MSEC;
  68         u32 val;
  69         int err;
  70
  71         /*
  72          * PWM Configuration register has SW_UPDATE bit that is set when a new
  73          * configuration is written to the register. The bit is automatically
  74          * cleared at the start of the next output cycle by the IP block.
  75          *
  76          * If one writes a new configuration to the register while it still has
  77          * the bit enabled, PWM may freeze. That is, while one can still write
  78          * to the register, it won't have an effect. Thus, we try to sleep long
  79          * enough that the bit gets cleared and make sure the bit is not
  80          * enabled while we update the configuration.
  81          */
  82         err = readl_poll_timeout(addr, val, !(val & PWM_SW_UPDATE), 40, ms);
  83         if (err)
  84                 dev_err(pwm->chip->dev, "PWM_SW_UPDATE was not cleared\n");
  85
  86         return err;
  87 }
  88
  89 static inline int pwm_lpss_is_updating(struct pwm_device *pwm)
  90 {
  91         return (pwm_lpss_read(pwm) & PWM_SW_UPDATE) ? -EBUSY : 0;
  92 }
  93
  94 static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm,
  95                              int duty_ns, int period_ns)
  96 {
  97         unsigned long long on_time_div;
  98         unsigned long c = lpwm->info->clk_rate, base_unit_range;
  99         unsigned long long base_unit, freq = NSEC_PER_SEC;
 100         u32 orig_ctrl, ctrl;
 101
 102         do_div(freq, period_ns);
 103
 104         /*
 105          * The equation is:
 106          * base_unit = round(base_unit_range * freq / c)
 107          */
 108         base_unit_range = BIT(lpwm->info->base_unit_bits);
 109         freq *= base_unit_range;
 110
 111         base_unit = DIV_ROUND_CLOSEST_ULL(freq, c);
 112         /* base_unit must not be 0 and we also want to avoid overflowing it */
 113         base_unit = clamp_val(base_unit, 1, base_unit_range - 1);
 114
 115         on_time_div = 255ULL * duty_ns;
 116         do_div(on_time_div, period_ns);
 117         on_time_div = 255ULL - on_time_div;
 118
 119         orig_ctrl = ctrl = pwm_lpss_read(pwm);
 120         ctrl &= ~PWM_ON_TIME_DIV_MASK;
 121         ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT);
 122         ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT;
 123         ctrl |= on_time_div;
 124
 125         if (orig_ctrl != ctrl) {
 126                 pwm_lpss_write(pwm, ctrl);
 127                 pwm_lpss_write(pwm, ctrl | PWM_SW_UPDATE);
 128         }
 129 }
 130
 131 static inline void pwm_lpss_cond_enable(struct pwm_device *pwm, bool cond)
 132 {
 133         if (cond)
 134                 pwm_lpss_write(pwm, pwm_lpss_read(pwm) | PWM_ENABLE);
 135 }
 136
 137 static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 138                           struct pwm_state *state)
 139 {
 140         struct pwm_lpss_chip *lpwm = to_lpwm(chip);
 141         int ret;
 142
 143         if (state->enabled) {
 144                 if (!pwm_is_enabled(pwm)) {
 145                         pm_runtime_get_sync(chip->dev);
 146                         ret = pwm_lpss_is_updating(pwm);
 147                         if (ret) {
 148                                 pm_runtime_put(chip->dev);
 149                                 return ret;
 150                         }
 151                         pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
 152                         pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false);
 153                         ret = pwm_lpss_wait_for_update(pwm);
 154                         if (ret) {
 155                                 pm_runtime_put(chip->dev);
 156                                 return ret;
 157                         }
 158                         pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true);
 159                 } else {
 160                         ret = pwm_lpss_is_updating(pwm);
 161                         if (ret)
 162                                 return ret;
 163                         pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period);
 164                         return pwm_lpss_wait_for_update(pwm);
 165                 }
 166         } else if (pwm_is_enabled(pwm)) {
 167                 pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE);
 168                 pm_runtime_put(chip->dev);
 169         }
 170
 171         return 0;
 172 }
 173
 174 static const struct pwm_ops pwm_lpss_ops = {
 175         .apply = pwm_lpss_apply,
 176         .owner = THIS_MODULE,
 177 };
 178
 179 struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
 180                                      const struct pwm_lpss_boardinfo *info)
 181 {
 182         struct pwm_lpss_chip *lpwm;
 183         unsigned long c;
 184         int ret;
 185
 186         if (WARN_ON(info->npwm > MAX_PWMS))
 187                 return ERR_PTR(-ENODEV);
 188
 189         lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
 190         if (!lpwm)
 191                 return ERR_PTR(-ENOMEM);
 192
 193         lpwm->regs = devm_ioremap_resource(dev, r);
 194         if (IS_ERR(lpwm->regs))
 195                 return ERR_CAST(lpwm->regs);
 196
 197         lpwm->info = info;
 198
 199         c = lpwm->info->clk_rate;
 200         if (!c)
 201                 return ERR_PTR(-EINVAL);
 202
 203         lpwm->chip.dev = dev;
 204         lpwm->chip.ops = &pwm_lpss_ops;
 205         lpwm->chip.base = -1;
 206         lpwm->chip.npwm = info->npwm;
 207
 208         ret = pwmchip_add(&lpwm->chip);
 209         if (ret) {
 210                 dev_err(dev, "failed to add PWM chip: %d\n", ret);
 211                 return ERR_PTR(ret);
 212         }
 213
 214         return lpwm;
 215 }
 216 EXPORT_SYMBOL_GPL(pwm_lpss_probe);
 217
 218 int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
 219 {
 220         int i;
 221
 222         for (i = 0; i < lpwm->info->npwm; i++) {
 223                 if (pwm_is_enabled(&lpwm->chip.pwms[i]))
 224                         pm_runtime_put(lpwm->chip.dev);
 225         }
 226         return pwmchip_remove(&lpwm->chip);
 227 }
 228 EXPORT_SYMBOL_GPL(pwm_lpss_remove);
 229
 230 int pwm_lpss_suspend(struct device *dev)
 231 {
 232         struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
 233         int i;
 234
 235         for (i = 0; i < lpwm->info->npwm; i++)
 236                 lpwm->saved_ctrl[i] = readl(lpwm->regs + i * PWM_SIZE + PWM);
 237
 238         return 0;
 239 }
 240 EXPORT_SYMBOL_GPL(pwm_lpss_suspend);
 241
 242 int pwm_lpss_resume(struct device *dev)
 243 {
 244         struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev);
 245         int i;
 246
 247         for (i = 0; i < lpwm->info->npwm; i++)
 248                 writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM);
 249
 250         return 0;
 251 }
 252 EXPORT_SYMBOL_GPL(pwm_lpss_resume);
 253
 254 MODULE_DESCRIPTION("PWM driver for Intel LPSS");
 255 MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
 256 MODULE_LICENSE("GPL v2");