drivers/pwm/pwm-bcm2835.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2014 Bart Tanghe <bart.tanghe@thomasmore.be>
   4  */
   5
   6 #include <linux/clk.h>
   7 #include <linux/err.h>
   8 #include <linux/io.h>
   9 #include <linux/module.h>
  10 #include <linux/of.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/pwm.h>
  13
  14 #define PWM_CONTROL             0x000
  15 #define PWM_CONTROL_SHIFT(x)    ((x) * 8)
  16 #define PWM_CONTROL_MASK        0xff
  17 #define PWM_MODE                0x80            /* set timer in PWM mode */
  18 #define PWM_ENABLE              (1 << 0)
  19 #define PWM_POLARITY            (1 << 4)
  20
  21 #define PERIOD(x)               (((x) * 0x10) + 0x10)
  22 #define DUTY(x)                 (((x) * 0x10) + 0x14)
  23
  24 #define PERIOD_MIN              0x2
  25
  26 struct bcm2835_pwm {
  27         struct pwm_chip chip;
  28         struct device *dev;
  29         void __iomem *base;
  30         struct clk *clk;
  31 };
  32
  33 static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
  34 {
  35         return container_of(chip, struct bcm2835_pwm, chip);
  36 }
  37
  38 static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
  39 {
  40         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  41         u32 value;
  42
  43         value = readl(pc->base + PWM_CONTROL);
  44         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  45         value |= (PWM_MODE << PWM_CONTROL_SHIFT(pwm->hwpwm));
  46         writel(value, pc->base + PWM_CONTROL);
  47
  48         return 0;
  49 }
  50
  51 static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
  52 {
  53         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  54         u32 value;
  55
  56         value = readl(pc->base + PWM_CONTROL);
  57         value &= ~(PWM_CONTROL_MASK << PWM_CONTROL_SHIFT(pwm->hwpwm));
  58         writel(value, pc->base + PWM_CONTROL);
  59 }
  60
  61 static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
  62                              const struct pwm_state *state)
  63 {
  64
  65         struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
  66         unsigned long rate = clk_get_rate(pc->clk);
  67         unsigned long long period;
  68         unsigned long scaler;
  69         u32 val;
  70
  71         if (!rate) {
  72                 dev_err(pc->dev, "failed to get clock rate\n");
  73                 return -EINVAL;
  74         }
  75
  76         scaler = DIV_ROUND_CLOSEST(NSEC_PER_SEC, rate);
  77         /* set period */
  78         period = DIV_ROUND_CLOSEST_ULL(state->period, scaler);
  79
  80         /* dont accept a period that is too small or has been truncated */
  81         if ((period < PERIOD_MIN) || (period > U32_MAX))
  82                 return -EINVAL;
  83
  84         writel(period, pc->base + PERIOD(pwm->hwpwm));
  85
  86         /* set duty cycle */
  87         val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle, scaler);
  88         writel(val, pc->base + DUTY(pwm->hwpwm));
  89
  90         /* set polarity */
  91         val = readl(pc->base + PWM_CONTROL);
  92
  93         if (state->polarity == PWM_POLARITY_NORMAL)
  94                 val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
  95         else
  96                 val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
  97
  98         /* enable/disable */
  99         if (state->enabled)
 100                 val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
 101         else
 102                 val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
 103
 104         writel(val, pc->base + PWM_CONTROL);
 105
 106         return 0;
 107 }
 108
 109 static const struct pwm_ops bcm2835_pwm_ops = {
 110         .request = bcm2835_pwm_request,
 111         .free = bcm2835_pwm_free,
 112         .apply = bcm2835_pwm_apply,
 113         .owner = THIS_MODULE,
 114 };
 115
 116 static int bcm2835_pwm_probe(struct platform_device *pdev)
 117 {
 118         struct bcm2835_pwm *pc;
 119         int ret;
 120
 121         pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
 122         if (!pc)
 123                 return -ENOMEM;
 124
 125         pc->dev = &pdev->dev;
 126
 127         pc->base = devm_platform_ioremap_resource(pdev, 0);
 128         if (IS_ERR(pc->base))
 129                 return PTR_ERR(pc->base);
 130
 131         pc->clk = devm_clk_get(&pdev->dev, NULL);
 132         if (IS_ERR(pc->clk))
 133                 return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
 134                                      "clock not found\n");
 135
 136         ret = clk_prepare_enable(pc->clk);
 137         if (ret)
 138                 return ret;
 139
 140         pc->chip.dev = &pdev->dev;
 141         pc->chip.ops = &bcm2835_pwm_ops;
 142         pc->chip.base = -1;
 143         pc->chip.npwm = 2;
 144         pc->chip.of_xlate = of_pwm_xlate_with_flags;
 145         pc->chip.of_pwm_n_cells = 3;
 146
 147         platform_set_drvdata(pdev, pc);
 148
 149         ret = pwmchip_add(&pc->chip);
 150         if (ret < 0)
 151                 goto add_fail;
 152
 153         return 0;
 154
 155 add_fail:
 156         clk_disable_unprepare(pc->clk);
 157         return ret;
 158 }
 159
 160 static int bcm2835_pwm_remove(struct platform_device *pdev)
 161 {
 162         struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
 163
 164         clk_disable_unprepare(pc->clk);
 165
 166         return pwmchip_remove(&pc->chip);
 167 }
 168
 169 static const struct of_device_id bcm2835_pwm_of_match[] = {
 170         { .compatible = "brcm,bcm2835-pwm", },
 171         { /* sentinel */ }
 172 };
 173 MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
 174
 175 static struct platform_driver bcm2835_pwm_driver = {
 176         .driver = {
 177                 .name = "bcm2835-pwm",
 178                 .of_match_table = bcm2835_pwm_of_match,
 179         },
 180         .probe = bcm2835_pwm_probe,
 181         .remove = bcm2835_pwm_remove,
 182 };
 183 module_platform_driver(bcm2835_pwm_driver);
 184
 185 MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be>");
 186 MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
 187 MODULE_LICENSE("GPL v2");