drivers/pwm/pwm-bcm2835.c

   1 /*
   2  * Copyright 2014 Bart Tanghe <bart.tanghe@thomasmore.be>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; version 2.
   7  */
   8
   9 #include <linux/clk.h>
  10 #include <linux/err.h>
  11 #include <linux/io.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/pwm.h>
  16
  17 #define PWM_CONTROL             0x000
  18 #define PWM_CONTROL_SHIFT(x)    ((x) * 8)
  19 #define PWM_CONTROL_MASK        0xff
  20 #define PWM_MODE                0x80            /* set timer in PWM mode */
  21 #define PWM_ENABLE              (1 << 0)
  22 #define PWM_POLARITY            (1 << 4)
  23
  24 #define PERIOD(x)               (((x) * 0x10) + 0x10)
  25 #define DUTY(x)                 (((x) * 0x10) + 0x14)
  26
  27 #define MIN_PERIOD              108             /* 9.2 MHz max. PWM clock */
  28
  29 struct bcm2835_pwm {
  30         struct pwm_chip chip;
  31         struct device *dev;
  32         unsigned long scaler;
  33         void __iomem *base;
  34         struct clk *clk;
  35 };
  36
  37 static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
  38 {
  39         return container_of(chip, struct bcm2835_pwm, chip);
  40 }
  41
  42 static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
  43 {
  44         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  45         u32 value;
  46
  47         value = readl(pc->base + PWM_CONTROL);
  48         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  49         value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
  50         writel(value, pc->base + PWM_CONTROL);
  51
  52         return 0;
  53 }
  54
  55 static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
  56 {
  57         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  58         u32 value;
  59
  60         value = readl(pc->base + PWM_CONTROL);
  61         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  62         writel(value, pc->base + PWM_CONTROL);
  63 }
  64
  65 static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  66                               int duty_ns, int period_ns)
  67 {
  68         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  69
  70         if (period_ns <= MIN_PERIOD) {
  71                 dev_err(pc->dev, "period %d not supported, minimum %d\n",
  72                         period_ns, MIN_PERIOD);
  73                 return -EINVAL;
  74         }
  75
  76         writel(duty_ns / pc->scaler, pc->base + DUTY(pwm->hwpwm));
  77         writel(period_ns / pc->scaler, pc->base + PERIOD(pwm->hwpwm));
  78
  79         return 0;
  80 }
  81
  82 static int bcm2835_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  83 {
  84         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  85         u32 value;
  86
  87         value = readl(pc->base + PWM_CONTROL);
  88         value |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
  89         writel(value, pc->base + PWM_CONTROL);
  90
  91         return 0;
  92 }
  93
  94 static void bcm2835_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
  95 {
  96         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  97         u32 value;
  98
  99         value = readl(pc->base + PWM_CONTROL);
 100         value &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
 101         writel(value, pc->base + PWM_CONTROL);
 102 }
 103
 104 static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
 105                                 enum pwm_polarity polarity)
 106 {
 107         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
 108         u32 value;
 109
 110         value = readl(pc->base + PWM_CONTROL);
 111
 112         if (polarity == PWM_POLARITY_NORMAL)
 113                 value &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
 114         else
 115                 value |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
 116
 117         writel(value, pc->base + PWM_CONTROL);
 118
 119         return 0;
 120 }
 121
 122 static const struct pwm_ops bcm2835_pwm_ops = {
 123         .request = bcm2835_pwm_request,
 124         .free = bcm2835_pwm_free,
 125         .config = bcm2835_pwm_config,
 126         .enable = bcm2835_pwm_enable,
 127         .disable = bcm2835_pwm_disable,
 128         .set_polarity = bcm2835_set_polarity,
 129         .owner = THIS_MODULE,
 130 };
 131
 132 static int bcm2835_pwm_probe(struct platform_device *pdev)
 133 {
 134         struct bcm2835_pwm *pc;
 135         struct resource *res;
 136         int ret;
 137
 138         pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
 139         if (!pc)
 140                 return -ENOMEM;
 141
 142         pc->dev = &pdev->dev;
 143
 144         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 145         pc->base = devm_ioremap_resource(&pdev->dev, res);
 146         if (IS_ERR(pc->base))
 147                 return PTR_ERR(pc->base);
 148
 149         pc->clk = devm_clk_get(&pdev->dev, NULL);
 150         if (IS_ERR(pc->clk)) {
 151                 dev_err(&pdev->dev, "clock not found: %ld\n", PTR_ERR(pc->clk));
 152                 return PTR_ERR(pc->clk);
 153         }
 154
 155         ret = clk_prepare_enable(pc->clk);
 156         if (ret)
 157                 return ret;
 158
 159         pc->scaler = NSEC_PER_SEC / clk_get_rate(pc->clk);
 160
 161         pc->chip.dev = &pdev->dev;
 162         pc->chip.ops = &bcm2835_pwm_ops;
 163         pc->chip.npwm = 2;
 164
 165         platform_set_drvdata(pdev, pc);
 166
 167         ret = pwmchip_add(&pc->chip);
 168         if (ret < 0)
 169                 goto add_fail;
 170
 171         return 0;
 172
 173 add_fail:
 174         clk_disable_unprepare(pc->clk);
 175         return ret;
 176 }
 177
 178 static int bcm2835_pwm_remove(struct platform_device *pdev)
 179 {
 180         struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
 181
 182         clk_disable_unprepare(pc->clk);
 183
 184         return pwmchip_remove(&pc->chip);
 185 }
 186
 187 static const struct of_device_id bcm2835_pwm_of_match[] = {
 188         { .compatible = "brcm,bcm2835-pwm", },
 189         { /* sentinel */ }
 190 };
 191 MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
 192
 193 static struct platform_driver bcm2835_pwm_driver = {
 194         .driver = {
 195                 .name = "bcm2835-pwm",
 196                 .of_match_table = bcm2835_pwm_of_match,
 197         },
 198         .probe = bcm2835_pwm_probe,
 199         .remove = bcm2835_pwm_remove,
 200 };
 201 module_platform_driver(bcm2835_pwm_driver);
 202
 203 MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be");
 204 MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
 205 MODULE_LICENSE("GPL v2");