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         void __iomem *base;
  33         struct clk *clk;
  34 };
  35
  36 static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
  37 {
  38         return container_of(chip, struct bcm2835_pwm, chip);
  39 }
  40
  41 static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
  42 {
  43         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  44         u32 value;
  45
  46         value = readl(pc->base + PWM_CONTROL);
  47         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  48         value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
  49         writel(value, pc->base + PWM_CONTROL);
  50
  51         return 0;
  52 }
  53
  54 static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
  55 {
  56         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  57         u32 value;
  58
  59         value = readl(pc->base + PWM_CONTROL);
  60         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  61         writel(value, pc->base + PWM_CONTROL);
  62 }
  63
  64 static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  65                               int duty_ns, int period_ns)
  66 {
  67         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  68         unsigned long rate = clk_get_rate(pc->clk);
  69         unsigned long scaler;
  70
  71         if (!rate) {
  72                 dev_err(pc->dev, "failed to get clock rate\n");
  73                 return -EINVAL;
  74         }
  75
  76         scaler = NSEC_PER_SEC / rate;
  77
  78         if (period_ns <= MIN_PERIOD) {
  79                 dev_err(pc->dev, "period %d not supported, minimum %d\n",
  80                         period_ns, MIN_PERIOD);
  81                 return -EINVAL;
  82         }
  83
  84         writel(duty_ns / scaler, pc->base + DUTY(pwm->hwpwm));
  85         writel(period_ns / scaler, pc->base + PERIOD(pwm->hwpwm));
  86
  87         return 0;
  88 }
  89
  90 static int bcm2835_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  91 {
  92         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  93         u32 value;
  94
  95         value = readl(pc->base + PWM_CONTROL);
  96         value |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
  97         writel(value, pc->base + PWM_CONTROL);
  98
  99         return 0;
 100 }
 101
 102 static void bcm2835_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 103 {
 104         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
 105         u32 value;
 106
 107         value = readl(pc->base + PWM_CONTROL);
 108         value &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
 109         writel(value, pc->base + PWM_CONTROL);
 110 }
 111
 112 static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
 113                                 enum pwm_polarity polarity)
 114 {
 115         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
 116         u32 value;
 117
 118         value = readl(pc->base + PWM_CONTROL);
 119
 120         if (polarity == PWM_POLARITY_NORMAL)
 121                 value &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
 122         else
 123                 value |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
 124
 125         writel(value, pc->base + PWM_CONTROL);
 126
 127         return 0;
 128 }
 129
 130 static const struct pwm_ops bcm2835_pwm_ops = {
 131         .request = bcm2835_pwm_request,
 132         .free = bcm2835_pwm_free,
 133         .config = bcm2835_pwm_config,
 134         .enable = bcm2835_pwm_enable,
 135         .disable = bcm2835_pwm_disable,
 136         .set_polarity = bcm2835_set_polarity,
 137         .owner = THIS_MODULE,
 138 };
 139
 140 static int bcm2835_pwm_probe(struct platform_device *pdev)
 141 {
 142         struct bcm2835_pwm *pc;
 143         struct resource *res;
 144         int ret;
 145
 146         pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
 147         if (!pc)
 148                 return -ENOMEM;
 149
 150         pc->dev = &pdev->dev;
 151
 152         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 153         pc->base = devm_ioremap_resource(&pdev->dev, res);
 154         if (IS_ERR(pc->base))
 155                 return PTR_ERR(pc->base);
 156
 157         pc->clk = devm_clk_get(&pdev->dev, NULL);
 158         if (IS_ERR(pc->clk)) {
 159                 dev_err(&pdev->dev, "clock not found: %ld\n", PTR_ERR(pc->clk));
 160                 return PTR_ERR(pc->clk);
 161         }
 162
 163         ret = clk_prepare_enable(pc->clk);
 164         if (ret)
 165                 return ret;
 166
 167         pc->chip.dev = &pdev->dev;
 168         pc->chip.ops = &bcm2835_pwm_ops;
 169         pc->chip.base = -1;
 170         pc->chip.npwm = 2;
 171         pc->chip.of_xlate = of_pwm_xlate_with_flags;
 172         pc->chip.of_pwm_n_cells = 3;
 173
 174         platform_set_drvdata(pdev, pc);
 175
 176         ret = pwmchip_add(&pc->chip);
 177         if (ret < 0)
 178                 goto add_fail;
 179
 180         return 0;
 181
 182 add_fail:
 183         clk_disable_unprepare(pc->clk);
 184         return ret;
 185 }
 186
 187 static int bcm2835_pwm_remove(struct platform_device *pdev)
 188 {
 189         struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
 190
 191         clk_disable_unprepare(pc->clk);
 192
 193         return pwmchip_remove(&pc->chip);
 194 }
 195
 196 static const struct of_device_id bcm2835_pwm_of_match[] = {
 197         { .compatible = "brcm,bcm2835-pwm", },
 198         { /* sentinel */ }
 199 };
 200 MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
 201
 202 static struct platform_driver bcm2835_pwm_driver = {
 203         .driver = {
 204                 .name = "bcm2835-pwm",
 205                 .of_match_table = bcm2835_pwm_of_match,
 206         },
 207         .probe = bcm2835_pwm_probe,
 208         .remove = bcm2835_pwm_remove,
 209 };
 210 module_platform_driver(bcm2835_pwm_driver);
 211
 212 MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be>");
 213 MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
 214 MODULE_LICENSE("GPL v2");