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