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/io.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19
  20 #include "pwm-lpss.h"
  21
  22 #define PWM                             0x00000000
  23 #define PWM_ENABLE                      BIT(31)
  24 #define PWM_SW_UPDATE                   BIT(30)
  25 #define PWM_BASE_UNIT_SHIFT             8
  26 #define PWM_BASE_UNIT_MASK              0x00ffff00
  27 #define PWM_ON_TIME_DIV_MASK            0x000000ff
  28 #define PWM_DIVISION_CORRECTION         0x2
  29 #define PWM_LIMIT                       (0x8000 + PWM_DIVISION_CORRECTION)
  30 #define NSECS_PER_SEC                   1000000000UL
  31
  32 struct pwm_lpss_chip {
  33         struct pwm_chip chip;
  34         void __iomem *regs;
  35         unsigned long clk_rate;
  36 };
  37
  38 /* BayTrail */
  39 const struct pwm_lpss_boardinfo pwm_lpss_byt_info = {
  40         .clk_rate = 25000000
  41 };
  42 EXPORT_SYMBOL_GPL(pwm_lpss_byt_info);
  43
  44 /* Braswell */
  45 const struct pwm_lpss_boardinfo pwm_lpss_bsw_info = {
  46         .clk_rate = 19200000
  47 };
  48 EXPORT_SYMBOL_GPL(pwm_lpss_bsw_info);
  49
  50 static inline struct pwm_lpss_chip *to_lpwm(struct pwm_chip *chip)
  51 {
  52         return container_of(chip, struct pwm_lpss_chip, chip);
  53 }
  54
  55 static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
  56                            int duty_ns, int period_ns)
  57 {
  58         struct pwm_lpss_chip *lpwm = to_lpwm(chip);
  59         u8 on_time_div;
  60         unsigned long c;
  61         unsigned long long base_unit, freq = NSECS_PER_SEC;
  62         u32 ctrl;
  63
  64         do_div(freq, period_ns);
  65
  66         /* The equation is: base_unit = ((freq / c) * 65536) + correction */
  67         base_unit = freq * 65536;
  68
  69         c = lpwm->clk_rate;
  70         if (!c)
  71                 return -EINVAL;
  72
  73         do_div(base_unit, c);
  74         base_unit += PWM_DIVISION_CORRECTION;
  75         if (base_unit > PWM_LIMIT)
  76                 return -EINVAL;
  77
  78         if (duty_ns <= 0)
  79                 duty_ns = 1;
  80         on_time_div = 255 - (255 * duty_ns / period_ns);
  81
  82         ctrl = readl(lpwm->regs + PWM);
  83         ctrl &= ~(PWM_BASE_UNIT_MASK | PWM_ON_TIME_DIV_MASK);
  84         ctrl |= (u16) base_unit << PWM_BASE_UNIT_SHIFT;
  85         ctrl |= on_time_div;
  86         /* request PWM to update on next cycle */
  87         ctrl |= PWM_SW_UPDATE;
  88         writel(ctrl, lpwm->regs + PWM);
  89
  90         return 0;
  91 }
  92
  93 static int pwm_lpss_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  94 {
  95         struct pwm_lpss_chip *lpwm = to_lpwm(chip);
  96         u32 ctrl;
  97
  98         ctrl = readl(lpwm->regs + PWM);
  99         writel(ctrl | PWM_ENABLE, lpwm->regs + PWM);
 100
 101         return 0;
 102 }
 103
 104 static void pwm_lpss_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 105 {
 106         struct pwm_lpss_chip *lpwm = to_lpwm(chip);
 107         u32 ctrl;
 108
 109         ctrl = readl(lpwm->regs + PWM);
 110         writel(ctrl & ~PWM_ENABLE, lpwm->regs + PWM);
 111 }
 112
 113 static const struct pwm_ops pwm_lpss_ops = {
 114         .config = pwm_lpss_config,
 115         .enable = pwm_lpss_enable,
 116         .disable = pwm_lpss_disable,
 117         .owner = THIS_MODULE,
 118 };
 119
 120 struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
 121                                      const struct pwm_lpss_boardinfo *info)
 122 {
 123         struct pwm_lpss_chip *lpwm;
 124         int ret;
 125
 126         lpwm = devm_kzalloc(dev, sizeof(*lpwm), GFP_KERNEL);
 127         if (!lpwm)
 128                 return ERR_PTR(-ENOMEM);
 129
 130         lpwm->regs = devm_ioremap_resource(dev, r);
 131         if (IS_ERR(lpwm->regs))
 132                 return ERR_CAST(lpwm->regs);
 133
 134         lpwm->clk_rate = info->clk_rate;
 135         lpwm->chip.dev = dev;
 136         lpwm->chip.ops = &pwm_lpss_ops;
 137         lpwm->chip.base = -1;
 138         lpwm->chip.npwm = 1;
 139
 140         ret = pwmchip_add(&lpwm->chip);
 141         if (ret) {
 142                 dev_err(dev, "failed to add PWM chip: %d\n", ret);
 143                 return ERR_PTR(ret);
 144         }
 145
 146         return lpwm;
 147 }
 148 EXPORT_SYMBOL_GPL(pwm_lpss_probe);
 149
 150 int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
 151 {
 152         u32 ctrl;
 153
 154         ctrl = readl(lpwm->regs + PWM);
 155         writel(ctrl & ~PWM_ENABLE, lpwm->regs + PWM);
 156
 157         return pwmchip_remove(&lpwm->chip);
 158 }
 159 EXPORT_SYMBOL_GPL(pwm_lpss_remove);
 160
 161 MODULE_DESCRIPTION("PWM driver for Intel LPSS");
 162 MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");
 163 MODULE_LICENSE("GPL v2");